Schneider Motor Protection System

Final Year Honours Thesis, 2017

By: Adam Jose Portillo Supervisor: Associate Professor Graeme Cole MURDOCH UNIVERSITY SCHOOL OF ENGINEERING AND INFORMATION TECHNOLOGY

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Abstract Faults occur in electrical systems and electrical wiring. A fault can result in minimal or

catastrophic consequences. Motor protection relays have been developed to detect the different

types of faults that can occur to a motor depending on the application of the motor. Today,

there are smart relays that can monitor the performance of the motor, perform calculations and,

detect different types of faults.

These smart relays come with their software that becomes a UMI (user-machine interface) to

the user, allowing them to constantly monitor the condition of the motor on a computer.

Different manufacturers have developed their smart relay which functions in different ways.

There are three motor protection units available at Murdoch University; two are from

Schneider, and the other one is from Schweitzer Engineering Laboratories (SEL’s).

The first part of this report covers the previous work that was done on the motor protection

system which is set up in the Pilot Plant of the Engineering and Energy building at Murdoch

University. The report also talks about the background of motor protection, faults that can occur

to a motor and, the different mechanisms employed in industries for motor protection.

The Schneider Sepam series m40 was used in this project to detect different faults going

through to the motor. The various functions, operating procedure of the Sepam series m40

system and the step by step approach followed to communicate with the Schneider protection

unit, detect various faults and, protect the motor from the detected faults are documented in

this report.

After completion of this project, two out of three faults were successfully simulated, and the

protection system was able to protect the motor from the simulated faults. The successfully

detected faults were the Undervoltage fault (fault 2) and the direction change fault (fault 3).

The Undercurrent fault (fault1) was not successfully simulated.

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Acknowledgements I would to firstly thank the staff and people who helped me complete my thesis. My thesis

supervisor Graeme Cole and technical staff Mark Burt, Will Stirling, Iafeta Lava (Jeff) and a

special thanks to Graham Malzer, for his assistances with wiring and his technical assistance

with my project.

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Table of Contents Abstract ................................................................................................................................................... i

Acknowledgements ............................................................................................................................... ii

Table of Figures..................................................................................................................................... v

Table of tables ...................................................................................................................................... vi

Author’s Declaration .......................................................................................................................... vii

Nomenclature ..................................................................................................................................... viii

1. Chapter 1: Project Overview ....................................................................................................... 1

1.1 Description of the Project ..................................................................................................... 2

1.2 Aim of the Project ................................................................................................................. 2

2. Chapter 2: Literature Review ...................................................................................................... 4

2.1 Background ........................................................................................................................... 4

2.1.1 Faults .............................................................................................................................. 4

2.1.2 Protection ....................................................................................................................... 6

2.2 Function of the Schneider Motor Protection System ....................................................... 13

3. Chapter 3: Method ...................................................................................................................... 15

3.1 Previous Work Done ........................................................................................................... 15

3.2 Structure of Work ................................................................................................................. 17

4. Chapter 4: Approach and Work to be Carried Out ............................................................... 19

4.1 Improvements that need to be made ................................................................................. 19

4.2 Testing .................................................................................................................................. 20

4.2.1 Parts Acquired............................................................................................................. 20

4.2.2 Test Circuit 1 ............................................................................................................... 21

4.2.3 Test Circuit 2 ............................................................................................................... 22

4.3 Other Improvements........................................................................................................... 23

5. Chapter 5: Implementation ....................................................................................................... 27

5.1 Control Circuit Wiring ....................................................................................................... 27

5.2 System Test .......................................................................................................................... 27

5.2.1 Test 1 ............................................................................................................................ 27

5.2.2 Test 2 ............................................................................................................................ 29

5.3 Using the Schneider Unit and Software SF2841 ............................................................... 29

5.3.1 Using the Schneider Unit ............................................................................................ 29

5.3.2 Using the Schneider Software SF2841....................................................................... 32

6. Chapter 6: Results ....................................................................................................................... 37

6.1 Fault 1 .................................................................................................................................. 37

6.2 Fault 2 .................................................................................................................................. 38

6.3 Fault 3 .................................................................................................................................. 41

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6.4 Result Summary .................................................................................................................. 44

7. Chapter 7: Future Works and Summary ................................................................................. 45

7.1 Future Works ........................................................................................................................ 45

7.1.1 Schneider Motor Protection System.............................................................................. 45

7.1.2 SEL’s Motor Protection System ................................................................................... 48

7.2 Conclusion ........................................................................................................................... 52

References ............................................................................................................................................ 53

Appendix A .......................................................................................................................................... 56

Appendix B .......................................................................................................................................... 59

Calculation for fault 1 ..................................................................................................................... 59

Calculation for fault 2 ..................................................................................................................... 60

Calculation for fault 3 ..................................................................................................................... 61

Appendix C .......................................................................................................................................... 62

Appendix D .......................................................................................................................................... 63

Drawing 1 Switchboard Equipment Layout ................................................................................. 65

Drawing 2: Push Button Inputs to Myrio ..................................................................................... 66

Drawing 3: Motor Control Circuit ................................................................................................ 67

Drawing 4: Motor Control Circuit Part 2 .................................................................................... 68

Drawing 5: SSR Terminal .............................................................................................................. 69

Drawing 6: Myrio Terminal ........................................................................................................... 70

Drawing 7: VT’s Circuit Power Diagram ..................................................................................... 71

Drawing 8: Current Input Connection ......................................................................................... 72

Drawing 9: Motor Fault Circuit Schematic Wiring Diagram.................................................... 73

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Table of Figures Figure 1: Schneider Series 40 [16] ....................................................................................................... 2

Figure 2: Main causes of motor damages in industry [6] .................................................................. 9

Figure 3: Protective functions to defect motor faults [6] ................................................................... 9

Figure 4: Modbus network configuration [7] ................................................................................... 12

Figure 5: CCA783 RS232 serial cable for the Sepam [7] ................................................................ 12

Figure 6: Block diagram of the Schneider Motor Protection System ............................................ 14

Figure 7: The previous work done by Christopher McGivern [5] ................................................. 15

Figure 8: Flowchart of work structure ............................................................................................. 17

Figure 9: Physical test circuit wiring ................................................................................................. 22

Figure 10: Test simulated circuit, replica of figure 9 ....................................................................... 22

Figure 11: Final control circuit wiring diagram .............................................................................. 23

Figure 12: Current wiring of the system ........................................................................................... 26

Figure 13: wiring of the system prior to this project [5] ................................................................. 26

Figure 14: Terminal block for the relay ............................................................................................ 28

Figure 15: Relay block that goes to the terminal block ................................................................... 28

Figure 16: Lights on the Sepam unit ................................................................................................. 30

Figure 17: General characteristics page on the SF2841 (Schneider Software) ............................. 34

Figure 18: Setting a fault on the SF2841 software ........................................................................... 34

Figure 19: The icons that are shown in the software ....................................................................... 36

Figure 20: Location of fault 1 in the circuit ...................................................................................... 37

Figure 21: Location of fault 2 in the circuit ...................................................................................... 38

Figure 22: Fault 2 undervoltage settings ........................................................................................... 39

Figure 23: Fault message of the fault is displayed on the Sepam screen ........................................ 40

Figure 24: The alarms displayed on the computer of the Schneider software alarms page,

displaying the fault, time and condition ............................................................................................ 40

Figure 25: The block diagram of how the fault works [7] ............................................................... 41

Figure 26: Location of fault 3 in the circuit ...................................................................................... 41

Figure 27: Block diagram of how the fault works on the Sepam [7] .............................................. 42

Figure 28: Fault 3 settings .................................................................................................................. 42

Figure 29: Fault 3 that is displayed on the Sepam ........................................................................... 43

Figure 30: The fault shown on the alarms page on the Sepam software ........................................ 43

Figure 31: Improvement made to the control circuit ...................................................................... 47

Figure 32: Improvements made to the control line .......................................................................... 47

Figure 33: The motors that would be used for the fourth fault [5] ................................................ 48

Figure 34: The wiring of the voltage and current transformers [12] ............................................. 50

Figure 35: Table 53 from AS/NZS 3008.1.1:2017 ............................................................................ 57

Figure 36: Table 54 from AS/NZS 3008.1.1:2017 ............................................................................ 57

Figure 37: The original circuit with the original resistor ................................................................ 59

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Table of tables Table 1: Contactor models for the faults and function .................................................................... 20

Table 2: The parameters that can be shown on the Sepam unit ..................................................... 30

Table 3: Definition of the lights from figure 16 ................................................................................ 31

Table 4: Messages of the faults sent from the Sepam to the computer .......................................... 32

Table 5: Definition of each icon on the Schneider software ............................................................ 36

Table 6: Comparison of calculation and datasheet result ............................................................... 38

Table 7: Measured voltage from the Sepam when fault 2 is applied .............................................. 39

Table 8: The result that would be seen when there is a direction change ...................................... 43

Table 9: Myrio Input connections ..................................................................................................... 62

Table 10: Myrio Output Connections ............................................................................................... 62

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Author’s Declaration I declare that this thesis is my own account of research and contains as its main content work

which has not previously been submitted for at any tertiary institution.

Adam José Portillo

Word Count Approximately 13, 148

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Nomenclature

Abbreviation Description

VSD Variable Speed Drive

GPO General Power Outlet

PLC Programmable Logic Controller

AC Alternating Current

DC Direct Current

VT Voltage Transformer

CT Current Transformer

VLL Voltage line to line

VLN Voltage Line to Neutral

UMI User Machine Interface

Wh Watt Hours

Vah Voltage Amp Hours

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1. Chapter 1: Project Overview It is important to protect all electrical equipment in an electrical circuit. The type of protection

mechanism employed depends on the equipment that is used, the type of protection that the

component requires, and the power rating of the components. If there is no protection in a

system, the consequences can be very high, which could lead to the damage of expensive

equipment. In electrical circuit design, it is important to have motor protection systems that

prevent electrical motors from overheating and faults that may develop slowly through time

which can lead to large consequences in the future.

Smart relays have been developed to protect motors from different faults that may occur to the

motor. Their function is to monitor and keep the user informed of the performance of the motor

at all times. These smart relays come with their software which is used to constantly send

information to a computer. When a fault occurs, the user can view it on the computer and after

the fault has been rectified, the user can reset the system through the computer back to normal

operating mode. Depending on the application of the motor, the user can set on the smart relay

the type of faults the system should detect. For example, the user can set the system to detect

an under-current or under-voltage fault.

The type of motor used for this project is a 3 phase squirrel cage star connected induction motor

rated at 3kW. The motor protection units that are available at Murdoch University are a

Schneider series m40, seen in figure 1, Schneider series 20 and a third motor protection unit

that is developed by SEL’s which is a different manufacturers protection unit that has the same

ability as the Schneider protection unit. The motor Protection relay that is going to be used for

this project is the Schneider Sepam m40, which is used to monitor both the current and the

voltage that is going to the motor.

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1.1 Description of the Project The Schneider Motor Protection System was previously worked on by students enrolled in the

ENG454 unit in semester 1, 2016 and by a previous thesis student (Christopher McGivern) in

semester 2, 2016. The aim of developing this system is to use it as a teaching tool in laboratory

classes for electrical power and industrial computer system engineering courses. This system

provides electrical protection to the motor to prevent the motor from getting damaged as a

result of the simulated faults. Both the Schneider and the SEL’s system simulates different

faults and detects the fault that has occurred in the circuit. The idea is for the SEPAM or the

SEL’s system to detect and display the fault that has occurred thereby alerting the operator that

a repair needs to be performed on the electrical system.

The project requires firstly to investigate how the system functions and also to familiarize with

the software and the equipment that is needed to run the Schneider system. Once the Schneider

system is operational, the SEL’s system can be developed, which would be used in the future

for teaching purposes.

1.2 Aim of the Project The aim of the project is to build the Schneider motor protection unit to simulate different faults

to a motor. The primary objective is to simulate three different types of faults. These faults

Figure 1: Schneider Series 40 [16]

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include: under-current, under-voltage, and change in direction fault. Once this primary

objective has been achieved, the fourth fault can be added to the system. A manual would be

developed to help students to easily and safely operate the system because as mentioned earlier,

the system would be used for teaching and learning purposes.

The manual which would be developed once the system is operational would include circuit

diagrams, instruction of how to include different faults to the system, changing parameters in

the software, operating the Schneider monitor and also, the safety requirements when operating

the system.

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2. Chapter 2: Literature Review This chapter focuses on the background information on faults, electrical systems protection,

motor protection, relay protection, smart relays, importance of protection in a system, and the

effects of not having protection in an electrical system. This chapter also contains a summary

of the previous work carried out on the two motor protection systems in the pilot plant.

2.1 Background

2.1.1 Faults

A fault is defined as an abnormal condition that causes a reduction in the basic insulation and

strength between phase conductors or between phase conductors and earth or any earthed

screens surrounding the conductors. Electrical systems are subject to many kinds of faults.

These faults can occur at the same instant at different points in the system or even in a different

phase. A fault would only be detected when there is an excess in current; reduction of

impedance between two conductors which becomes a value that is below that of the lowest

load impedance to the normal circuit [1].

There are different ways that a fault can eventually occur, such as: punctured or broken

insulators, open circuit conductors, abnormal loading, mechanical damage, accidental contact

with earth or earthed screens or flashover in the air caused by over-voltages [1].

When operating motors and rotating electrical equipment, it is important to take into

consideration the possible failures that may occur in the equipment. However, the frequency

of failures to occur in generators and large motors are low, but the monetary consequence of a

failure can be serious [3]. Listed below are the different faults that can occur in a motor or in

an electrical system that need to be detected:

Over-voltage

Over-current

Winding Faults

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Voltage Unbalances

Current Unbalances

Under-voltage

Phase Interruption

Over-voltage- This is the condition when the voltage is greater than the rated voltage; this

would normally damage electric and electronic devices [4]. Overvoltage would affect the

motor’s cores due to excess of flux produced inside the magnetic circuit; causing the flux to

saturate the core, producing high eddy current losses in the core which may cause internal

damages to the motor from over excitation [3].

Over-current- This condition can occur when the current is higher than the rated current of the

motor; caused by a short circuit, loose connection or by a ground fault [4].

Winding Faults- An important part of a motor are the windings that are inside a motor. The

temperature of the motor windings can increase if they operate for such a long time, which can

affect the life span of the motor [4]. Due to the heat applied to the windings of the motor, over

time, the insulation on the windings can breakdown. This could result in shorting the windings

to the earthed housing of the motor that can cause short circuits [5].

Voltage Unbalances- This would happen when the magnitude of the phase or the line voltages

are different, and the phase angles are different from a balanced load. This would then cause

speed variation, additional losses, and current unbalances [4].

Current Unbalances- This can also result from voltage unbalances, which leads to higher losses

due to circulating currents in the windings that can cause bearing failures to the motor and there

is an increase of heat in the motor [4].

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Under Voltage- When the voltage is low, it prevents the motor from obtaining its rated speed

once it has started. Therefore, it losses speed and draws in more current which also increases

the temperature of the windings. [3].

Phase Interruption- This is when one of the three phases is interrupted, and two of the three

phases are used to run the motor [4].

A fault happening in a motor can result in serious consequences in a company. Therefore, it is

important to have protection in motors to prevent any faults from occurring. If the fault is still

connected, the whole power system remains at risk. For power generation, a fault can affect

different groups of generators in a different station to synchronism; a risk in damaging a healthy

plant by an affected plant [6].

2.1.2 Protection

Faults in electrical systems can result in serious consequences that may affect the electrical

service that is being provided to a consumer or the electrical equipment that is used to run the

system. Hence, protection is important to ensure maximum return on the equipment invested,

thereby keeping the user satisfied with a reliable power system. This would allow the power

system to be running continuously without any major breakdowns [1].

Without protection, it is impossible to operate any power system. The function and importance

of protection are to remove as fast as possible any affected element or equipment of the power

system [6]. For a power system to be safe or fit to continuously run, the system must adopt

components that are durable and require little maintenance. Another way is to predict any

possible faults that may occur that can cause the power system to shut down for a long time

[6].

To install a protection system that will be suitable for a particular power system, it is important

that the protection system meets the requirements of the power system. The protection

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component has three main functions, they are: to ensure the safety of personnel, minimize

damage and repair expenses, and safeguard the whole system to maintain continuous operation.

Other requirements for a protection system to be suitable for the first detection and localization

of the faults are: selectivity- isolating and detecting the faulty component; stability- to leave

the circuits intact and continuously operating; sensitivity- being able to detect even the smallest

fault or short circuit currents; speed- to operate as fast as possible; dependable- the protection

must trip when it is supposed to; and secure- it must not trip when there is not a fault [6].

Some examples of protection components include: fuse- a self-destructive protection device

that consist of a wire carrying current during normal operation and would blow up when there

is abnormal current flowing through the wire, causing the circuit to break. The second example

of a protection component is a circuit breaker, it allows current to flow through the breaker in

normal operating conditions. However, if abnormal current passes through the breaker, it would

trip instantly thereby breaking the circuit. The breaker helps to isolate the electrical system

from the power supply so the user can remove the faulty component or equipment. The circuit

can be reset to normal conditions once the fault has been cleared. To attain accurate voltage

and current measurements to assess whether the system is healthy or not, voltage and current

transformers are used to obtain these measurements. Relays are also used to isolate the circuit

by opening any faulty circuits in the power system [6].

2.1.2.1 Relay Protection

Relays or otherwise known as protective relays can take corrective action as quickly as possible

when an abnormal condition is detected in the power system and would then return the power

system to its normal conditions; where power systems are liable to disturbances that occur

through arbitrary load changes and faults are created usually from equipment or operator

failure. The essential requirement of a relay protection system is speed. This allows any

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protective intervention to occur automatically and with minimal disruption to the power system

and without any human intervention [6].

However, having a relay protection system does not necessarily mean that an equipment in the

electrical system cannot go bad because if electrical equipment is used for a long period and

not managed properly, it become damaged due to wear and tear. When this happens, the

protection system can only then detect the damage and then react to prevent any further damage

from happening to any other equipment in the system [3].

The control aspect of a relay protection system requires an operator who would then return the

system to an acceptable condition by making sure the fault has been cleared from the power

system, and this has to be done as quickly as possible. The reliability of a relay protection

system is known as the measure of the degree of certainty that a component would work to its

expectation. Relays are different to other equipment in terms of reliability because relays can

be unreliable in two different ways; they can fail to operate when they are expected to, or they

can operate when they are not supposed to. A reliable relay protection system must be

dependable and secure. Relay protection dependability is defined as a measure of the certainty

that relays will not operate incorrectly for any fault. Most protection relay systems are designed

for dependability [3].

2.1.2.2 Motor Protection Relay

Motors are widely used in the industry; they are described as the "Workhorse of industry"

because they can convert electrical power into mechanical power. A particular type of motor

that is commonly used is the Squirrel cage induction motor because of their small, rugged

construction, and good starting and running torque. However, there are some motors that can

get damaged either by faults occurring in the electrical circuitry or other reasons According to

ABB Group, statistics gathered on the causes of motor damage shown in figure 2 [6].

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Figure 3 below, shows the protective functions that are needed to detect motor faults according

to the ABB group. From the graph, it can be seen that 81% of these failures could have been

avoided if accurate and effective relay protection system were in place [6].

The life of a motor is determined by two factors; the mechanical and the electrical life of the

motor. Mechanical life is the life of the mechanical components which consist of the bearings,

shaft, fan, and frame. The electrical life of a motor consist of the stator winding, insulation and

26%

30%20%

5%

19%

Long Time OverheatingInsulaiton FaultRotor or Bearing FaultFaulty ProtectionOther Causes

Figure 2: Main causes of motor damages in industry [6]

26%

30%

20%

5%

19%

Thermal overload protection

Short-circuit and earth fault protection

Start-up supervision and thermal sensor unit

Continous self-testing of the protective relay

Other protective functions/undetectable faults

Figure 3: Protective functions to defect motor faults [6]

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making sure that all wiring connections are made properly and regularly checked. The electrical

life of the motor can be extended by ensuring that the windings and insulation are not under

such excessive temperatures that can create overloading and loss of phase fault. A good motor

protection system would continuously monitor the current going into the motor. This would

detect any overloading fault conditions and automatically disconnect the motor when there is

an abnormal condition. If the right protection system is installed, it would extend the life of the

motor and prevent future damages [6].

Early designs of motor protection relay consisted of having a single function with the purpose

of protecting the motor from overloading and to guarantee that it wouldn’t draw excess current

than its rated current. This was achieved by continuously monitoring the current that would go

into the motor. If the current exceeds the rated current, then it would disconnect the motor

thereby preventing it from overheating. An example of this type of protection relay is the

‘solder pot’ relay, which counted the time taken for the solder in the circuit to melt. The melted

time of the solder depends on the current passing through the circuit and that melting time was

used by the relay to determine if the motor is operating at the rated current or not. Another

example is the bi metal type relay which disconnects the motor when the load current passing

through a resistor heated in the bi metallic strip sufficiently bends it beyond from the preset

limit. Hence, protection is based on monitoring the phase currents [6].

2.1.2.3 Smart Relay Protection

Smart protection relays or more commonly known as microprocessor relays are an improved

version of the electromechanical relays and are more accurate and reliable. They are digital

electronic relays that perform calculations based on pre-programmed series of instructions and

measured current and voltage signals to determine if there is an abnormal condition in the

electrical system. They protect themselves by isolation through a transformer; limiting the

voltage and the current to protect internal circuits of the relay from being destroyed [6].

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Electromechanical relays are designed for a particular application and have specified current

limit, while smart relays can be used for multiple applications and do not have a specified

current limit. The accuracy of a smart relay is greater than that of an electromechanical relay;

where the accuracy of an electromechanical relay would depend on the frequency and

harmonics which could affect the readings, the accuracy of the smart relay depends on the

voltage and current readings from the measurement transformers [6].

Most smart relays come with a digital display, allowing the user to monitor the electrical power

system. These devices come with relay settings that can be adjusted by either potentiometers

or through a software application on a computer. The measured value of various parameters

can be seen on a digital display in a cyclic order. If a fault occurs and the smart relay breaks

the circuit to protect the electrical equipment, it stores the value of the measured parameters as

at when the fault occurs in its memory. This is useful because this information can later be used

to assist in any analysis of the cause of the fault [6].

2.1.2.3.1 Schneider Protection Relay

Schneider protection relay, can protect from or trigger different faults, such as: under-voltage,

directional active over-power, remanent over-power, positive sequence under-voltage and

phase rotation directional check, phase undercurrent, temperature monitoring, negative

sequence unbalances, broken conductor, negative sequence overvoltage, excessive starting

time, locked rotor, thermal overload, etc. The level of protection depends on the Schneider

protection unit. The Schneider system can also be connected to a Modbus network allowing

multiple systems to be connected in one electrical system, as seen in figure 4. The Schneider

protection relay has its software to change current parameters and limits in the electrical system

[7].

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The Schneider protection system comes with a software which is a UMI used to monitor the

performance of the motor. The current set point, voltage set point, and the winding rating of

the voltage and current transformers can be set through the software so the system will be able

to give accurate readings. Through the software and depending on the application that the motor

is used for, the user can set different faults that may potentially affect the motor once it is

running. Using the parameters read from the electrical system, the protection unit can calculate

the positive and negative sequence voltages and based on that calculation, the protection unit

will be able to trigger different faults. The protection unit is connected through a CCA783 cable

that is similar to an RS232 serial cable. The computer can communicate to the module and

receive real-time data and the system is setup in a master-slave configuration. Figure 5 shows

the construction of the RS232 cable.

Figure 4: Modbus network configuration [7]

Figure 5: CCA783 RS232 serial cable for the Sepam [7]

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2.1.2.3.2 SEL Protection Relay

The SEL protection relay is designed to protect small, medium or large three-phase motors and

can detect different faults, such as: under and over voltage, under-power, under and over

frequency, read reactive power and power factor, over-current, current unbalances, motor

thermal, breaker failure logic, and phase reversal. Similar to the Schneider motor protection

unit, they are connected in a master and slave configuration where the system is always reading

and sending measured parameters to the computer. Also, this unit comes with its own software

where the user can configure different faults and monitor the motor as it is running. The SEL’s

motor protection unit software is called AcSelerator Analytic Assistant. Also, in the same

software, the user can view the performance of the motor graphically either through a phasor

diagram animation or by waveform graph analysis.

2.2 Function of the Schneider Motor Protection System The basic function of the Schneider Motor protection system is best described through the

block diagram in figure 6. The system is controlled by the control circuit or by the computer

through the LabVIEW program. The SSR block is used isolate the voltages from the output of

the Myrio card which uses 3.3V and the contactors that make use of 24VDC. When the start

button is pressed, the forward contactor would be activated and at the same time, the voltage

and current transformers are reading the voltage and current going to the motor. If one of the

fault buttons is pressed, one of the contactors is latched and the voltage and current transformers

would read the values going through to the motor. The Sepam would read the abnormal

condition and trigger the protection relay which is normally closed to open. This would break

the circuit and therefore disconnect the motor from the power supply.

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Figure 6: Block diagram of the Schneider Motor Protection System

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3. Chapter 3: Method The first part of this chapter talks about the previous work that was started on both of Schneider

and SEL’s motor protection unit and the faults that both systems were simulating. This chapter

also includes a flow chart of the work carried out in this project.

3.1 Previous Work Done The Schneider Motor Protection system was worked on by Christopher McGivern in semester

2, 2016 for his final thesis project. At the end of his project, he was able to organise the system

in a server box, seen in figure 7. The Sepam was placed in front of the server box along with

the control buttons. The three-phase motor was placed inside the server box along with the

protection relay and input/output Myrio card. The system was designed in such a way that it

could be controlled either by a computer or by fixed physical buttons in front of the server box.

Figure 7: The previous work done by Christopher McGivern [5]

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The system was designed to simulate three different faults (fault1, fault 2 and fault 3). Fault 1

was a current imbalance fault, where a resistor was placed in series with phase 1 to cause a

change in current to the motor. Fault 2 was a loss of phase fault, which was achieved by

disconnecting phase 3 from the motor. This would only leave phase 1 and 2 connected to the

motor. The third fault that the system was designed to simulate was the change in direction

fault. When fault three button is pressed, phase 1 and three would be swapped which would

cause the motor to change its direction.

However, the system did not function as required. The Sepam failed to detect any of the

simulated faults, rather, whenever the fault was activated, the VSD connected to the motor

would shut down [5]. Another issue that the system had was that when the system was running

under normal operating conditions, the Sepam was reading the wrong voltages and this error

was documented in Christopher McGivern thesis report [5]. Also, an improvement had to be

made on the change in direction fault control circuit. This is because upon closer examination

of the circuit, it was discovered that if the change in direction fault was activated, it would go

straight to the motor and it can potentially damage the motor. Thus a control circuit with an

electrical interlock between the two directions would have to be developed.

The SEL’s motor protection system was developed by students enrolled in ENG454 in semester

1, 2015. This system was built as a standalone system on a table top inside the pilot plant. A

program written into the Moeller PLC was used to simulate different faults to the motor. The

faults that were simulated in the SEL's system were: over-current, earth fault, thermal overload,

locked rotor, load jam, phase reversal, current unbalance and under-voltage. The main

difference between the SEL’s and Schneider protection system is that the SEL’s system makes

use of a Moeller PLC, while the Schneider system makes uses of a Myrio card.

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3.2 Structure of Work The flow chart in figure 8 below shows the step by step approach that was followed to complete

this project.

Figure 8: Flowchart of work structure

Revision of the system

wiring and understanding

how the system was built

Rewire and reconstruction

of the system

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The first step involves studying and understanding the Schneider motor protection system. To

identify all major components, such as: voltage and current transformers, VSD, Schneider

Sepam motor protection unit, Myrio, lights, voltage supplies, motor, electrical main switch,

circuit breakers and 24V power supply. To verify if the wiring of each component conforms to

what is mentioned in the manual. Finally, to analyse the system to determine what needs to be

improved and the components needed to make the system operational.

As mentioned in section 3.1 (previous work done) of this report, the control circuit for the

change in direction fault did not include a mechanical interlock which is necessary to prevent

the motor from getting damaged. The second step of this project has to do with redesigning the

control circuit to include the mechanical interlock. This would be done initially on a small scale

without any connection of three-phase power or the three-phase motor. Once the small-scale

control circuit has been tested, it would be installed on the main Schneider protection unit.

Upon completion of the second step, it will be necessary to procure the required components

to make the installation of the control circuit possible. The procurement of these components

would be the third step of this project.

The fourth step of this project would be to install the control circuit in the main protection

system. This will be done with caution because of the three-phase power connected to the main

system. However, another test of the control circuit would be carried out with only the DC

voltage supply connected to the system to make sure that the control circuit is properly wired.

After verification of the control circuit connection, the three-phase power will be connected to

the system.

The final step of this project would be connecting the motor to the protection system and testing

the system to verify if it would detect the simulated faults. Also, a manual would be developed

which will contain details on how the system should be operated.

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4. Chapter 4: Approach and Work to be Carried Out This chapter summarizes the necessary change that need to be implemented on the system. It

also talks about the testing approach that was followed in testing the system and why some

components were not suitable for the system.

4.1 Improvements that need to be made After studying the previous work done on the system, some changes had to be done on the

system to make it operable. The wiring of the system was messy and too difficult to determine

which wire connects to which device. It would be dangerous to operate the system in that

manner. Thus, the system had to be rewired and inspected by a technical staff (because of the

415V used by the three-phase motor).

The control circuit also needed to be adjusted. Previously, the control that was developed had

no electrical interlock between the forward and reverse of the motor. A control circuit with an

electrical interlock had to be developed to prevent the motor from getting damaged if a change

in direction was suddenly initiated. The new control circuit would make use of momentary

push buttons rather than toggle switches because it is easier to incorporate a push button in a

control circuit than it is using a toggle switch.

The relays that were installed in the system for switching 415V supply of the motor were only

rated at 250VAC (underrated) and therefore, needed to be replaced to prevent the relays from

getting damaged. A 4P circuit breaker would need to be purchased to protect the voltage

transformers and the Sepam protection unit from any short circuit current or voltage spikes.

Graham Malzer, a Murdoch University technical staff examined the system and realised that

the system was not properly earthed. This means that before the system could be operated, the

system would have to be properly earthed. Also, as mentioned in Christopher McGivern’s

thesis report, the voltage readings of the voltage transformers were not accurate.

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To make the system ok to operate, all the components would need to be suitably rated for the

system and the control circuit would have to be adjusted to include the following:

When the start and stop button are pressed at the same time, the motor must not start.

Electrical interlock between the forward and reverse direction of the motor.

A reset button to disable and to clear the fault.

Integrate the emergency stop button into the circuit.

A Sepam trip circuit.

Momentary push buttons.

4.2 Testing

4.2.1 Parts Acquired

Contactors rated at 230VAC were acquired for the auxiliary blocks and contactors rated at

460V were acquired for the three phase contacts. Two contactors with mechanical interlock

capabilities suitable for switching the motor direction and three contactors suitable for

implementing the faults were found in the engineering storeroom.

Table 1: Contactor models for the faults and function

Function Brand Model

Fault 1 Schneider LCI D09 BD

Fault 1- Trip Allen Bradley LCI D09 BD

Fault 2 Allen Bradley 100-CA3E*100

Forward Allen Bradley 100-CA3E*100

Fault 3 Allen Bradley 100-CA3E*100

E-Stop Allen Bradley C30D00C

Trip Circuit Schneider CAD 32 BD

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Fault 1 requires two contactors, one to switch off phase 1 line and the other contactor to switch

to a different line which is parallel to the main line causing the current to go through a 150Ω

resistor. One of the contactors would remain normally closed and would be activated once the

system is energised. When the fault 1 button is pressed, the contactor would be deactivated and

the other contactor would be activated. Fault 2 required one contactor to disconnect phase 3

thereby causing a loss of phase fault. Once the system is energised, the reset button has to be

pressed and all contactors have to be in their initial condition before the motor is turned on to

prevent the motor from getting damaged. Fault 3 makes use of the two contactors that are

mechanically interlocked. If one of the contactor is enabled, the other contactor cannot be

activated because of the mechanical interlock. The control circuit was designed to include an

electrical interlock so that it would be impossible to reverse the motor when it is in the forward

direction.

4.2.2 Test Circuit 1

A test control circuit was developed to make sure it is done properly on the main system. The

LabVIEW program was developed in such a way that if the start and stop button are pressed at

the same time, the motor would not start. A reset button was included in the control circuit to

clear the faults and to reset the contactors so that the system can be restarted. Previously, two

separate relays were used to start and stop the system. One of the relays was removed because

a single relay can be used for the purpose of starting and stopping the system. The system was

also adjusted in such a way that the start button cannot start the system without the LabVIEW

program. This means that when the start button is pushed, a signal is sent to the LabVIEW

program and the LabVIEW program would then activate a SSR block to start the system.

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4.2.3 Test Circuit 2

A similar test circuit was developed using iCircuit computer software to simulate the control

circuit to identify areas that need improvement and to test the electrical interlocking of the

system. The simulated circuit is a replica of the physical circuit shown in figure 9. The circuit

had to be developed because the previous circuit had been dismantled and was necessary to

make sure that the interlock between the forward and reverse of the motor had been done

properly.

Figure 9: Physical test circuit wiring

Figure 10: Test simulated circuit, replica of figure 9

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4.3 Other Improvements The emergency stop circuit was also improved. The previous E-Stop circuit was only

implemented in LabVIEW program and not hardware implemented. The emergency stop

contactor was placed on the three phase power supply line before the circuit breakers. Using

one of the normally closed contacts of the emergency stop button, 24VDC was fed to the

emergency stop contactor. A strobe light which is controlled by the Myrio card through a SSR

block was installed to indicate the status of the emergency stop button. When the emergency

button is pressed, a contactor will disconnect the three phase supply to the system, shutdown

the LabVIEW program, and activate the strobe light.

The Sepam output trip circuit was developed using an output of the Sepam protection unit. The

output of the Sepam can be set as normally closed or normally open through the program logic

page of the Sepam software. For this project, the output that was used for the trip circuit is set

Figure 11: Final control circuit wiring diagram

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to normally closed. The output of the Sepam is used to control the motor contactor, seen in

figure 11. When the run SSR is activated and the Sepam output (set as normally closed) is not

activated, the three phase motor will start. However, if a fault is triggered, the Sepam output

will open which will de-energise the motor contactor and cause the motor to stop.

The LabVIEW program was developed and saved on the Myrio card and so the system does

not require for the user to download the program. If the power supply is disconnected and then

reconnected, the user would have to wait for a couple of seconds until the blue light on the

Myrio card inside the cabinet begins to flash; the flashing blue is the indication that the program

is running and the system can be operated. In the event that the emergency stop button is

pushed, the mains power has to be switched off before the emergency stop button is released.

Another alteration that was made to the wiring was the fault indication lights. The fault

indication light were wired in parallel to the relay coils that control the faults. Therefore, if the

relay is broken and the fault is activated, the indication light will turn on but the fault will not

be activated because of the broken relay. To rectify this, the indicator lights were wired to the

auxiliary contactors that control the faults. This way, the indicator lights can only come on if

the fault contactors are functional.

Further analysis of the system showed that the voltage transformers were not wired according

to the directions given in the manual. When a multimeter was used to check the voltage reading

of the voltage transformers, the reading was incorrect as the expected voltage reading of

415𝑉𝐿−𝐿 was not displayed on the multimeter. Wrongly connecting the voltage transformers

will make the Sepam protection unit not to function properly. The voltage transformers were

rewired following the instructions in the manual and a multimeter was used to measure the

voltage. A voltage reading of 415𝑉𝐿−𝐿 was displayed on the multimeter screen which means

25 | P a g e

that the voltage transformers have now been wired properly and therefore, the Sepam would

get accurate readings from the voltage transformers which is very important.

The current transformers were also rewired. Initially, they were placed upstream from the VSD

which would give false readings for the detection of faults. The current transformers have now

been placed downstream of the VSD so that is can properly detect any change in current. Star

configuration was used in connecting the current transformers. For noise mitigation, the system

had to be properly earthed. The earthing of the system had to be done according to AS/NZS

3000:2007 which requires all the rails and cabinet to be earthed. Before running the system,

proper evaluation and insulation test has to be done.

The circuit breakers installed on the system were rated at 6kA but the circuit breakers installed

in the Pilot Plant are rated at 10kA. To make sure that the 6kA circuits were well suited for the

system, a calculation (shown in appendix A) was done to determine the short circuit current of

the system. The result of this calculation showed that the 6kA circuit breakers are suitable for

the system. An additional four pole circuit breaker was purchased to protect the Sepam from

any voltage spikes that may occur in the circuit. The 6kA circuit breaker that was previously

installed on the system was installed at the main power supply to the system for the full system

protection.

All major three-phase and single-phase components do not need to be changed but the wiring

of some of the components require adjustments. Also, new components would have to be added

to the system. The colour of the DC wires would also be changed because both the 24VDC and

phase 1AC wires were red colour which made troubleshooting difficult. Violet coloured wires

would be used to replace the red wires of the 24VDC wiring because it can easily be

distinguished from red wires and the violet wires will have the same thickness and current

rating as the three-phase wires.

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Previously, the motor was placed on the floor of the cabinet. A decision was made to move it

outside the cabinet to make space for other components. A Three-phase outlet was placed on

side of the cabinet so that the motor can be connected to it. Another reason for moving the

motor outside is that by placing a three-phase connector outside the cabinet, different motors

can be connected to the system with the use of a plug as the Sepam is capable of monitoring

different types of motors. To power the 24VDC supply from the UNO power unit, another

general point outlet (GPO) was placed next to the GPO that was there previously. The wiring

was done neatly and spaced as best as possible. Figure 13 shows the previous wiring of the

system while figure 13 shows the current wiring of the system. Labels were also used for the

wiring to make it easier to troubleshoot.

Figure 13: wiring of the system prior to this project [5] Figure 12: Current wiring of the system

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5. Chapter 5: Implementation This chapter discusses how the control circuits were developed and tested before running the

system. It talks about the various changes that were made to the previous circuit and the results

obtained from the system test.

5.1 Control Circuit Wiring The contactors that were used for the test circuit were installed on the floor of the Schneider

system. Fault 1 resistor was placed on the side walls of the cabinet. Once all the auxiliaries for

the contactors, the violet wire, momentary contact buttons, and other components were

acquired, the 24VDC wiring of the system began. Wiring of the control circuit was done using

the wiring diagram that was developed during the initial test of the control circuit. The wires

for the control circuit were changed to purple, old terminal blocks were removed, new terminal

blocks were installed and bridging links were used were necessary.

5.2 System Test

5.2.1 Test 1

Before proceeding with the implementation of this project, an external DC power supply was

used to test the control circuit to determine if further adjustments needed to be made to the

circuit. During this phase, it was discovered that relay RK1 and K9 were not properly wired.

Figure 15 shows +ve and –ve of the relay coil while Figure 14 shows A1 and A2 of the terminal

block which the relay coils plug into. When attached together, the -ve of the relay coil connects

to A1 and the +ve of the relay coil connects to A2 but, A1 is meant for +ve connection of a

relay coil and A2 is meant for –ve connection of a relay coil. Because the terminal block and

the relay coil did not match accordingly (polarity), there was a short circuit inside the relay coil

causing the system to draw a lot of current from the power source. To rectify this, the

connection was done with respect to the polarity shown on the relay coil and not the relay

terminal block.

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Figure 14: Terminal block for the relay

Figure 15: Relay block that goes to the terminal block

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5.2.2 Test 2

After the 24VDC and three-phase wiring was complete, the system was tested without

connecting the motor. Immediately the power was supplied to the system, the VSD triggered

the main circuit breaker in the Pilot Plant. This circuit breaker trip was because the VSD was

interfering with other electrical components in the system. It was later discovered (after further

study of the VSD manual) that the earthing requirement of the VSD is different from that of

the systems in the Pilot Plant. For this reason, the VSD was removed from the Schneider

Protection system. Removing the VSD means that the motor will jump when power is supplied

to the motor because the VSD provides a starting sequence for the motor which prevents the

initial jump of the motor on start-up.

Using a multimeter, the voltage at the voltage transformers was measured to compare the

measured values to that displayed on the Sepam. The primary and secondary winding of the

voltage transformers were set in the Sepam software. The general characteristics page of the

Sepam software allows the user to set both windings.

5.3 Using the Schneider Unit and Software SF2841

5.3.1 Using the Schneider Unit

The Schneider Protection unit, also known as the Sepam Series 40 m40, monitors the

performance of the motor. Once the Sepam unit is powered, the first thing it displays is the

measured current. Pressing the metering button on the Sepam will make the Sepam display the

current in different ways (current in each phase, maximum current, average current). If the

metering button is held down, a display will come up on the Sepam which shows a page where

the user can select what should be displayed on the Sepam monitor. Table 2 shows the different

parameters the user can choose to display.

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Table 2: The parameters that can be shown on the Sepam unit

Parameter Display

Voltage Phase-Phase Voltage

Phase to Neutral Voltage

Phase-Phase Voltage as a graph

Zero Sequence Voltage

Current Current in each Phase

Maximum Current

Average Current

Zero Sequence Current

Sum of the Current

Power Active Power

Reactive Power

Apparent Power

Power Factor

Maximum Active Power and Maximum

Reactive Power

Frequency Measures the Frequency in Hertz

Energies Active power in Wh

Reactive Power VAh

The Sepam series 40 is the device which will be used in this project to detect the different

faults. This protection unit has four outputs which are located at the back of the Sepam unit.

When there is a fault, all four outputs are triggered. On the opening page of the software, the

logic of each output can be changed to suit a particular application. For this project, each output

has been set to carry out a different function when a fault occurs. There are a series of lights on

the top bar of the unit. Table 3 shows what each light shown in figure 16 represents.

Figure 16: Lights on the Sepam unit

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Table 3: Definition of the lights from figure 16

Led Indicator Front Panel Label Meaning

On Power On

Spanner Module Unavailable

Led 1 I > 51 Tripping of protection 50/51 unit 1

Led 2 I >> 51 Tripping of protection 50/51 unit 2

Led 3 IO > 51N Tripping of Protection 50N/51N

unit 1

Led 4 IO >> 51N Tripping of Protection 50N/51N

unit 2

Led 5 Ext

Led 6

Led 7 Circuit Breaker Open (I11)’

Led8 Circuit Breaker Closed (I12)’

Led 9 Trip Tripping by circuit control

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5.3.2 Using the Schneider Software SF2841

The type of protection that the Sepam unit can provide is based on the type of unit that is

purchased. Different Sepam units provide different types of protection. Listed in table 4 below

are the type of protection that the Sepam unit used in this project can provide.

Table 4: Messages of the faults sent from the Sepam to the computer

Type of Fault Message Display of Sepam and sent to the

Computer

ANSI Code

Under-voltage Undervoltage 27/27S

Positive Sequence under-

voltage and phase rotation

direction check

Undervoltage. PS 27D/47

Rotation

Remanent Under-voltage 27R

Directional active over-power Reverse P 32P

Directional reactive over-power Reverse Q 32Q/40

Phase undercurrent Under Current 37

Temperature monitoring 38/49T

Negative sequence/ Unbalance Unbalance I 46

Broken Conductor Broken Conduct 46BC

Negative sequence over-voltage Unbalance V 47

Excessive starting time, locked

rotor

Rotor Blocking 48/51LR/14

STRT LockedROTR

Thermal Overload Thermal Alarm 49 RMS

Thermal Trip

Start Inhibit

Phase over-current Phase Fault 50/51

Phase over-current cold load

Pick-Up/Blocking

50/51

Breaker Failure 50BF

Earth Fault Earth Fault 50N/51N

Earth Fault Cold load Pick-

Up/Blocking

50N/51N

Voltage Restrained phase over-

current

O/C V Restraint 50V/51V

Over-voltage Overvoltage 59

Neutral voltage displacement V0 Fault 59N

Start per hour 66

Directional phase overcurrent Dir. Phase Fault 67

Directional earth fault Dir. Earth Fault 67N/67NC

Recloser Final Trip 79

Cleared Fault

Over-frequency Over Freq. 81H

Under-frequency Under Freq 81L

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The first column of table 4 shows the type of protection the unit can provide. The second

column shows the message that will be displayed on the Sepam unit when one of the faults is

detected. This message will also be sent to the computer and displayed on the alarms page of

the software so that the operator can identify the fault. The ANSI code which represents each

fault is shown in column three of table 4.

The American National Standard Institute also known as ANSI developed a code for functions

that are used in switching or protective relaying systems by using appropriate letters and

numbers to determine what type of function is defined in a protective device [3]. For example,

a fault can be known as 50N/51N. The ‘’50’’ represents the fault or function of the protective

device, the ‘’/’’ can mean that it has a double function, and the ‘’51N’’ means the fault number

is 51 and it’s related to neutral or earth fault. Therefore, if the protection unit display shows

50N/51N when a fault occurs, it means that the fault that has occurred is an earth fault.

A CCA783 cable would be used to connect the Sepam protection unit to a computer. The

Sepam is set up in a master slave communication configuration with the computer as the master

of the network. Data is sent from the Sepam to the computer upon request from the computer.

The Sepam software becomes a user machine interface (UMI) to the user where the user can

monitor the performance of the motor. Some of the parameters that the user can monitor are

the voltage, current, and frequency that is going to the motor. Also, the user can change

different parameters such as; the windings of the current transformers, and the phase to phase

voltage reading at the primary and secondary winding of the voltage transformer. The voltage

that is set on the primary winding of the voltage transformer becomes the set-point voltage and

the set base current which is based on the selected current transformer becomes the set-point

current as shown in figure 17. For this project, the voltage reading at the primary winding of

the voltage transformers is 406V and the Crompton 781-943 current transformer windings are

100/5.

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Depending on the application of the motor, the user can set on the software which faults should

be monitored by the Sepam protection unit. Also, the user can select what action the Sepam

unit should take if a fault occurs. Figure 18 shows the three options the user can choose from.

Figure 17: General characteristics page on the SF2841 (Schneider Software)

Figure 18: Setting a fault on the SF2841 software

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On: This tells the Sepam to monitor a particular fault. If the ‘’on’’ box is unchecked as

it is in figure 18, the Sepam would not do anything if that fault occurs. Also, if the ‘’on’’

box is checked and others are unchecked, the Sepam will display the fault if it occurs

but would not trip the circuit breaker which means that the motor would keep running.

Latching: If the latching and trip CB box are checked, the Sepam has to be physically

reset either by the push button on the monitor or through the software even if the fault

that occurred has been cleared.

Trip CB: Selecting this option means that the Sepam would trip the circuit if a fault

occurs. However, if the latching box is unchecked, the motor can start running when

the fault is cleared and the start button is pushed.

Element 1 and 2: Some faults have two elements and some have one. This option allows

the user to configure the Sepam to detect either one or two conditions associated with

a fault. Therefore, if element 1 does not occur, the Sepam would monitor the motor for

element 2.

Delay: When a fault occurs, the user can set the Sepam to react to the fault after a certain

period. This period can be in milliseconds or seconds.

Voltage Threshold: The voltage threshold is the percentage of deviation from the

voltage set point allowed before the Sepam detects a fault. From figure 18, the positive

sequence under-voltage threshold has been set for 15% which means that if the positive

sequence voltage is below 15% of the set point voltage, the Sepam would detect an

under-voltage fault and take the necessary action required to deal with the fault.

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There are different tabs with different icons on the Sepam software that represent different

pages and settings. Table 5 shows what each icon represent on figure 19.

Table 5: Definition of each icon on the Schneider software

Number Function or Page

1 Sepam Parameters

2 Protection

3 Equations

4 Matrix

5 Function

6 Sepam Diagnosis

7 Metering

8 Network Diagnosis

9 Switchgear Diagnosis

10 Alarms

11 Fault Recording

Figure 19: The icons that are shown in the software

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6. Chapter 6: Results This chapter talks about the results obtained from the simulation of the three different faults

developed in this project. Also, this chapter mentions what was displayed on the Schneider

motor protection unit. The motor that was connected to the system to simulate the different

faults is an Asea 3kW three-phase squirrel cage motor. How the different faults work and how

the Sepam unit detects these fault is discussed in this chapter.

6.1 Fault 1 Fault 1 is a fault that changes the current in one of the phase (phase 1) of the three-phase supply

to the motor. A contactor is used to activate this fault by making the current flow through a

resistor thereby causing a reduction in the current on that phase. When this fault was activated,

the resistor used for the fault exploded. The datasheet of the resistor was again studied and it

was discovered that the 150Ω resistor would need to have a heat sink attached for it to have a

power dissipation rating of 150W (suitable for this application). The resistor was not fitted with

a heat sink which made the power dissipation rating fall to 55W (not suitable for this

application) resulting in the explosion of the resistor. Figure 20 shows the wiring diagram of

fault 1.

Figure 20: Location of fault 1 in the circuit

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There were two other resistors available (100Ω and 50Ω). Contained in appendix A of this

report is the full calculation that was carried out to determine the power dissipation at the

resistor when the fault is applied. Table 6 shows a comparison between the calculated power

dissipated at the resistor and the rated power of the other two resistors that were available.

Table 6: Comparison of calculation and datasheet result

From table 8, it is obvious that the calculated power is higher than the rated power. Hence, this

fault could not be implemented.

6.2 Fault 2 This is a loss of phase fault. A contactor (shown in figure 21) placed in series with phase 3 is

used for this fault. When fault 2 is activated, the contactor disconnects phase 3 from the motor

supply which results in an under-voltage fault. The voltage readings obtained when this fault

was simulated is shown in table 7 below.

Figure 21: Location of fault 2 in the circuit

Resistor (Ω) Rated Power (W) Rated Power without Heatsink (W) Calculated Power (W)

50 50 20 52.24

100 100 50 104

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Table 7: Measured voltage from the Sepam when fault 2 is applied

Line Voltage Line to Line (VL-L) Line Voltage (VLN)

V21 426 V1 245

V32 367 V2 247

V13 391 V3 191

The voltage at line 3 fell below 85% of the line to neutral voltage set point and the line to line

voltage fell below 96% of the voltage set point (calculations in appendix A). Figure 22 shows

the setting in the software for the under-voltage fault. The Sepam was set to detect a fault if the

phase to phase or line to line voltage falls below 95% of the set point voltage.

From figure 22, the Sepam has been set to monitor both element 1 which is the line to line

voltage and element 2 which is the line to neutral voltage conditions. Figure 24 shows the

display of the Sepam unit and the indicator lights on the Schneider protection unit when this

fault was simulated.

Figure 22: Fault 2 undervoltage settings

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Once the under-voltage fault was detected, the Sepam sent a message to the computer to inform

the user that the fault has occurred. This message was also displayed on the Sepam unit as seen

in figure 23. ANSI code 27/27S which means that one of the supply lines of the motor has been

affected represents this fault. Figure 24 shows the message displayed on the alarms page of the

software.

Figure 23: Fault message of the fault is displayed on the Sepam screen

Figure 24: The alarms displayed on the computer of the Schneider software alarms page, displaying the fault, time and condition

41 | P a g e

The block diagram shown below shows the condition for which the Sepam unit is configured

to detect the fault. According to the diagram, if the voltage on any of the phases drop below

the set point voltage, the Sepam would detect the fault.

6.3 Fault 3 Fault 3 is the change of direction fault. The two contactors used to implement this fault have

both mechanical and electrical interlock to prevent damage to the motor. This fault could not

be implemented with the use of a button because of the placement of the voltage transformers

in the circuit. The contactors connected to the circuit for implementing the change of direction

fault were placed after the voltage transformers connection as seen in figure 26. Therefore, if

the contactors swap phase 1 and phase 3, the voltage transformers would not be able to detect

it. However, this fault was simulated manually by swapping the power supply lines before the

voltage transformers connection so that the voltage transformers can detect the change.

Figure 25: The block diagram of how the fault works [7]

Figure 26: Location of fault 3 in the circuit

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Referring to the block diagram in figure 27, there are two conditions for the change of direction

fault to be detected. The first condition is the positive sequence voltage. A percentage in the

range of 15% to 60% can be selected as the positive sequence voltage threshold. If 20% is

selected, the Sepam would monitor the system for when the positive sequence voltage falls

below 20% of the set point voltage. The second condition is the line to line voltage. The Sepam

would monitor the system for when the line to line voltage falls below the line to neutral voltage

set point. If both conditions are fulfilled, the Sepam would trip.

For this project, the positive sequence under-voltage was set to 15% (as seen in figure 28).

When the system is operating under normal conditions, the positive sequence voltage remains

at 247V but when phase 1 and 3 supply lines were swapped, the positive sequence voltage

became 0 which caused the Sepam to trip.

Figure 27: Block diagram of how the fault works on the Sepam [7]

Figure 28: Fault 3 settings

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Table 8: The result that would be seen when there is a direction change

The message that was displayed on the Sepam when this fault was simulated is Undervolt P.S

ANSI code 27D. The fault message was also displayed on the alarms page of the software as

shown in figure 30.

Positive Sequence Voltage Without Positive Sequence Voltage

With Fault

Reading 247 0

Figure 29: Fault 3 that is displayed on the Sepam

Figure 30: The fault shown on the alarms page on the Sepam software

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6.4 Result Summary How the various faults were simulated have been discussed in this chapter. Wiring diagrams

have been presented to show how various components like voltage transformers, current

transformers, and contactors have been wired in order to simulate the different faults.

Implementation of fault 1 was not successful because of the power rating of the available

resistor. Fault 2 and 3 were implemented successfully but only fault 2 could be implemented

with the use of the fault 2 button. Fault 3 was implemented manually by swapping phase 1 and

3 of the three-phase supply because of the position of the voltage transformers.

This chapter also talked about the communication of the Sepam with the computer. When a

fault occurs, the Sepam trips and disconnects the power supply to the three-phase motor and

sends a message to the computer to inform the user that a fault has occurred. The message sent

to the computer also contains information about the type of fault that has occurred, the time the

fault occurred, and on which phase the fault occurred. Negative sequence/current unbalance

fault was another fault that was detected but not documented during this project. The fault was

as a result of fault 2 because when one of the three phase was disconnected, the current going

to the motor was also affected.

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7. Chapter 7: Future Works and Summary This chapter talks about the work that is yet to be done on the Schneider protection unit and a

summary of the works that has been done for this project. Some of the future works require a

bit more investigation while others require the purchase and installation of components. Also,

this chapter mentions the SEL’s protection unit which is another type of motor protection unit

and the work that has been done on the SEL’s system. There are some recommendations

given in this chapter on how to improve the Schneider protection system.

7.1 Future Works

7.1.1 Schneider Motor Protection System

7.1.1.1 Replacement of the Resistor for fault 1

A suitable resistor required to successfully implement fault 1 has to purchased and installed on

the system. All the resistors available do not have the required power rating to implement fault

1. In case it is not possible to purchase a new resistor, the 100Ω resistor available in the Pilot

plant can be used if fitted with a large enough heat sink or by use of an alternative method

(need to be investigated) to cool the resistor to prevent it from exploding. Also, care has to be

taken if it is decided to fit the resistor with a heat sink to make sure that the heat sink will be

of good standard so that the resistor can dissipate power at its full potential.

Currently, this fault has been disconnected. The push button used to activate this fault still

works and if pushed, will energise the contactor and turn on the fault indicator light but the

current won’t go through the resistor, hence, there is no change in the current. A 100Ω and 50Ω

resistor are currently inside the system but are not connected. All that is required is to connect

a suitable resistor and fault 1 can be simulated.

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7.1.1.2 VSD Implementation

The VSD that was initially used for the system was interfering with the electrical equipment in

the Pilot plant thereby causing the circuit breaker to trip. As stated in chapter 5 of this report,

the VSD earthing requirement is different from that used in the Pilot Plant. It would be

advisable to purchase a VSD that has the same earthing requirements as the systems in the Pilot

Plant. With the use of a VSD, over-frequency and under-frequency fault can also be simulated.

Currently, the VSD in the Schneider system has been bypassed and was not used for the final

implementation of this project.

Also, a VSD is needed for the motor to start smoothly. When three-phase power is supplied

directly to the motor, it starts with a sudden jump because of the jump in current and torque. A

VSD will allow the motor to have a starting sequence thereby eliminating the initial jump that

occurs when power is supplied directly to the motor. The SEL’s system makes use of a SEW

VSD which has the same earthing requirement as the systems in the Pilot Plant.

7.1.1.3 Position of the Voltage transformers

Another change that will be necessary is the change of the position of the voltage transformers.

The voltage transformers are placed before the contactors that are used to swap phase 1 and

phase 2 of the three-phase supply to the motor. Hence, the voltage transformers will not detect

the swap of phase which is used to simulate the change in direction fault. The voltage

transformers were put in the position they are right now because they are constantly feeding

voltage readings to the Sepam and if there is no voltage reading, the Sepam would detect an

under-voltage fault.

To solve this issue, an alteration will have to be made to the control circuit using the normally

closed condition in the auxiliary blocks of both the forward and backward contactor used for

fault 3 (change of direction fault). Also, it would be required to obtain another contactor that

would be energised once the run button is pushed. This third contactor would be able to provide

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constant voltage to the Sepam and would be able to detect the change of direction fault. Shown

in figure 31 and 32 are the proposed circuit diagrams that can be used for simulating fault 3.

Figure 31: Improvement made to the control circuit

Figure 32: Improvements made to the control line

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7.1.1.4 Additional Faults

There are some additional faults that can be simulated with this system. A motor can be

attached to the main motor with the use of a belt. The attached motor will become an external

load for the main motor. A similar set-up was developed for the SEL’s motor protection system.

An adaptor would have to be attached to one of the motors as shown in figure 33 to be able to

plug it into the Schneider system three-phase power supply outlet. With the addition of an

external load and proper system configuration, the Schneider system would be able to detect

faults like over-voltage (ANSI code 59) and excessive starting time (ANSI code 48/51LR/14)

fault.

7.1.2 SEL’s Motor Protection System

7.1.2.1 Previous Work

The SEL’s motor protection system was last worked on by ENG 454 students in 2015.

Currently, the SEL’s protection unit is on a table inside the Pilot Plant. Some of the components

used in the SEL’s system have been used in this project for the Schneider protection unit. The

SEL’s protection unit which is similar to the Schneider protection unit was developed by

Shweitzer Engineering Laboratories. Faults like under-voltage, over-voltage, under-frequency,

over-frequency, and direction change can also be detected by the SEL’s protection unit.

Figure 33: The motors that would be used for the fourth fault [5]

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7.1.2.2 Required Components

It is advisable that an understanding of the Schneider protection system be developed before

moving on to the SEL’s system. Some main components required for the SEL’s system are;

voltage transformers, current transformers, and 6kA rated circuit breakers for the power

requirement of the system. A four pole circuit breaker is also needed to protect the SEL’s

protection unit from any voltage spikes that may come from the voltage transformers. Some

available components include; a VSD which is necessary for smooth starting of the motor, and

a box of 2Ω resistors which would be useful for fault simulations. However, further calculations

have to be carried out to determine if the available resistors are suitable for simulating the fault

in order to prevent the resistors from exploding the same way it happened during the execution

of this project. The available resistors are from the same manufacturers of the resistor that

exploded.

7.1.2.3 Voltage and Current Transformers

The voltage and current transformers would have to be connected into a star configuration as

the motor is connected in a star configuration (seen in figure 34). The SEL’s system can make

use of the same type of voltage transformers used for the Schneider system. However, the

current transformers used for the Schneider system are old and difficult to find. It would be

preferable to purchase a new current transformer for the SEL’s system. The model of the

voltage transformer used for the Schneider system is a Block USTE 100/2x115 voltage

transformer and the winding of the current transformer is 100A/5A.

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7.1.2.4 Using the Myrio

Either a Moeller or Myrio would be suitable for the SEL’s system. The advantage of using a

Myrio is that it has already been used for the Schneider system. Also, LabVIEW program is

available on almost all the computers in the Engineering building. There were difficulties

encountered by Christopher McGivern during his final thesis when he tried to connect the

Moeller PLC to the computer but making the same connection was easy using a Myrio as long

as the Myrio and LabVIEW program on the computer are the same version. With a Myrio, it is

also possible to interlock the direction change of the motor using the software. The main

disadvantage of the Myrio card is that SSR blocks have to be used to isolate the voltage from

the Myrio to the control circuit.

7.1.2.5 Control Circuit

The relays currently used in the SEL’s system to conduct the faults has to be replaced

because they are rated at 250VAC and the three-phase line to line voltage is 415V.

Contactors with the necessary rating and 24VDC coil are recommended for this system. Two

Allen Bradley 100-CA3E contactors can be used for the change of direction fault because

Figure 34: The wiring of the voltage and current transformers [12]

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they have mechanical interlock which is necessary to prevent damage to the three-phase

motor.

A new control circuit would have to be developed to include the new contactors. The

contactors should be wired in such a way that they will latch once a fault button is activated.

Previously, the ENG 454 students that worked on the SEL’s system made use of toggle

switches but momentary switches are used mostly in industries. It would also be advisable to

include indicator lights to signal which particular fault has occurred. The indicator lights can

be triggered by the outputs of the SEL’s protection unit. Also, it should only be possible to

start the motor when all the faults have been cleared except for the change of direction fault.

7.1.2.6 Other Functions and Signalling

An emergency stop would have to be added to the system as there was none connected when

the ENG 454 students worked on the system. The emergency stop has to be included both

physically using a contactor and in the Myrio program. A strobe light like the one used in the

Schneider system can be used to indicate when the emergency stop has been activated. It is

also recommended that the emergency stop contactor be placed at the point where the three-

phase power is supplied to the system.

Another contactor can be used for the trip circuit. An output of the SEL’s protection unit should

be set as normally closed using the SEL’s program that comes with the unit. This output would

be placed in series with the start sequence SSR output or the start circuit; a circuit similar to

that of the Schneider system trip circuit. See appendix D, drawing 3. It would also be good to

place the system in a cabinet. All the components can be put in the cabinet, wired neatly and

labelled appropriately. The wires can be colour coded according to what voltage the wire is

carrying. For three-phase voltage the standard red, blue and white can be used and another

different colour for the 24VDC voltage.

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The system should be properly wired, locked and tested before running the system. It is

recommended that the system should be locked when the three-phase power is connected in

order to prevent any harm to individuals. Only technical staffs should be able to remove the

cabinet lock and make sure the system has been isolated from three-phase power before any

student can work on the system. A user manual should also be developed for future users of

the system to help them understand how the system works.

7.2 Conclusion Overall, the Schneider protection system is electrically safe as it has been properly sealed. Only

authorized personnel can gain access to the system to make required changes. This document

provides a manual that explains how to run the system and includes a brief description of how

the system works. All the wires inside the cabinet have been labelled according to the circuit

diagrams to make it easier to troubleshoot. Before working on the system, the three-phase plug

has to be disconnected and padlocked and the student has to consult with one of the technical

staffs. Changes to the DC part of the circuit can be tested using an external power supply unit.

All changes made to the system has to be revised by a technical staff before running the system.

The Schneider system currently has no out of service tag as all components are fully functional.

The program developed for the system has been saved on the Myrio card. Hence, it is not

necessary to plug the Myrio card to the computer but the user will have to wait for 10 seconds

after power is supplied to the system before the program starts to run. The system has gone

through an insulation test and can be used to run the motor safely. All the drawings of the

system have been updated. The Schneider protection system still needs some improvements

and details about the various improvements has been documented in the future works section

of this report.

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References

[1] A. o. I. o. E. E. Electricity Training, Power system protection, London : Institution of

Electrical Engineers, 1995.

[2] Y. Gritli, L. Zarri, C. Rossi, F. Filippetti, G. Capolino and D. Casadei, "Advanced

diagnosis of electrical faults in wound-rotor induction machines," IEEE Transactions

on Plasma Science, vol. 41, no. 8, p. 4012, 2013.

[3] H. Horowitz and G. Phadke, Power system relaying, vol. 3rd, Chichester,

England;Hoboken, NJ;: John Wiley & Sons/Research Studies Press, 2008.

[4] O. Uyar and M. Çunkaş, "Fuzzy logic-based induction motor protection system,"

Neural Computing and Applications, vol. 23, no. 1, pp. 31-40, 2013.

[5] C. McGivern, "Design and implementation of a standalone motor protection relay

apparatus," 2016.

[6] L. Hewitson, M. Brown and B. Ramesh, Practical power system protection, Burlington,

MA;Oxford;: Elsevier/Newnes, 2004.

[7] S. Electric, Sepam Series 40 Protective User Manual, 2007.

[8] Y. Zhang, "SEL Motor Protection System: SEL701-1 monitor," 2014.

[9] M. Zahri, Y. Menchafou, H. El Markhi and M. Habibi, "Simplified method for single

line to ground-fault location in electrical power distribution systems," Internation

Journal of Electrical and Computer Engineering , vol. 5, no. 2, pp. 221-230, 2015.

[10] M. Yazdani-Asrami, M. Taghipour-Gorjikolaie, S. Mohammad Razavi and S. Asghar

Gholamian, "A novel intelligent protection system for power transformers considering

54 | P a g e

possible electrical faults, inrush currents, CT saturation and over-excitation,"

International Journal of Electrical Power and Energy Systems, vol. 64, pp. 1129-1140,

2015.

[11] R. Torres, A. Hagphanah, T. Bower, R. Delay and R. Paes, "Adjustable speed drives

and motor protection," 2014.

[12] SEL, "SEL-701 Motor Protection Relay," 2007.

[13] H. Saadat, Power system analysis, Sydney;Boston;: McGraw-Hill Primis Custom, 2002.

[14] P. C. M. Lamim Filho, F. B. Batista, R. Pederiva and V. A. D. Silva, "Electrical fault

diagnosis in induction motors using local extremes analysis," Journal of Quality in

Maintenance Engineering, vol. 22, no. 3, pp. 321-332, 2016.

[15] K. Jia, E. Christopher, D. Thomas, M. Sumner and T. Bi, "Advanced DC zonal marine

power system protection," IET Generation, Transmission & Distribution, vol. 8, no. 2,

pp. 301-309, 2014.

[16] J. Glover, M. Sarma and J. Overbye, Power system analysis and design, Stamford, CT:

Cengage Learning, 2012.

[17] C. Christopoulos and A. Wright, Electrical power system protection, London;Boston;:

Kluwer, 1999.

[18] C. R. Bayliss, Transmission and distribution electrical engineering, Oxford;Boston;:

Elsevier/ Newnes, 2012.

[19] S. Bagheri, Z. Moravej and G. B. Gharehpetian, "Effect of transformer winding

mechanical defects, internal and external electrical faults and inrush currents on

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performance of differential protection," IET GENERATION TRANSMISSION &

DISTRIBUTION, vol. 11, no. 10, pp. 2508-2520, 2017.

[20] B.n.d, Control Isolating Transformer USTE 100/2x115.

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Appendix A Calculating the short circuit current.

Purpose: Calculate maximum short circuit current of 35mm2 4C&E cable based on thermal

consideration

Method: Calculation based on AS/NZS 3008.1.1:2017 Section 5 pp.120-123

Assumptions were for this calculation; they were:

1. Fault clearing time does not exceed 50 cycles (or 1 second)

2. PVC/PVC Cable insulation

3. Maximum temperature 160°C (Table 53)

4. Maximum temperature 200°C (Table 54)

Data

From AS3008 Table 52

Temp Initial = 75°C

Temp Final K = 160°C (Table 53 <=300mm2 cable), table shown in figure 36

Temp Final K = 200°C (Table 54), table shown in figure 35

S = CSA = cable CSA in mm2 =35

Hence, K = 111(160°C) or 140 (200°C)

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Figure 35: Table 53 from AS/NZS 3008.1.1:2017

Figure 36: Table 54 from AS/NZS 3008.1.1:2017

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Calculation for the short circuit current

𝐼2𝑡 = 𝐾2𝑆2

Where: t= 1, K1=111, K2=140, S<-35 and K=K1

Substituting the values into the equation above:

Solving for I1

𝐼1 < − (1112 × 352

1)

0.5

𝐼1 < 3885

Solving for I2

𝐼2 < − (1402 × 352

1)

0.5

𝐼2 < 4900

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Appendix B

Calculation for fault 1

Converting line to line to line to neutral

𝑉𝐿𝑁 =𝑉𝐿−𝐿

√3=

415.0

√3

𝑉𝐿𝑁 = 239.6

Finding the Motor Resistance with the current in the line I=2.84

𝑅𝑀𝑂𝑇𝑂𝑅 =𝑉𝐿𝑁

𝐼=

239.6

2.84

𝑅𝑀𝑂𝑇𝑂𝑅 = 84.36

Figure 37: The original circuit with the original resistor

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Calculation for fault 2 Voltage Line to Line set point

𝑉𝐿𝐿 = 406

For Line to Line voltage (Element 2)

According to table 9 when fault 2 is applied the line to line is affected to V13 & V23, then:

𝑉13 = 367𝑉 & 𝑉23 = 391𝑉

Therefore, the percentage drop is then, using V23:

𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 = 391.0

406× 100

𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 = 96.30%

For Line to Neutral voltage (Element 2)

Converting it to line to neutral

𝑉𝐿𝑁 =𝑉𝐿−𝐿

√3=

406.0

√3

𝑉𝐿𝑁 = 234.4

According to Table 9, when fault 2 is applied to line 3, the voltage in line 3 drops to:

𝑉3 = 191.0

Therefore, the percentage drop is then

𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 = 191.0

234.4× 100

𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 = 81.62%

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Calculation for fault 3 For fault 3 it requires to calculate the positive sequence voltage, the equation below

𝑉1 =1

3(𝑉𝐴𝑁 + 𝑉𝐵𝑁𝑎 + 𝑉𝐶𝑁𝑎2)

Where: 𝑎 = 1 120°

Voltages are from the Sepam monitor

VAN = 2470°

VBN = 247 − 120°

VCN = 247 120°

Calculation of the positive sequence voltage

𝑉1 =1

3(𝑉𝐴𝑁 + 𝑉𝐵𝑁𝑎 + 𝑉𝐶𝑁𝑎2)

= 1

3(2470 + 247 − 120°(1 120°) + 247120°(1 240°)

𝑉1 = 247 0°

When line VBN are switched with VCN

Therefore: VAN = 2470°

VBN = 247120°

VCN = 247 − 120°

Then the positive sequence voltage would then be:

𝑉1 =1

3(𝑉𝐴𝑁 + 𝑉𝐵𝑁𝑎 + 𝑉𝐶𝑁𝑎2)

= 1

3(2470 + 247120°(1 120°) + 247 − 120°(1 240°)

𝑉1 = 0

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Appendix C Myrio Input & Output Connections

Inputs

Table 9: Myrio Input connections

Outputs

Table 10: Myrio Output Connections

Function MyRio Outputs

SSR Block Number Pin Number Output Number

Run 13 A/DIO1 IN1

Stobe Light 19 A/DIO5 IN2

Reset 17 A/DIO3 IN3

Fault 1 34 A/DIO15 IN4

Fault 2 32 A/DIO14 IN5

Fault 3 29 A/DIO9 IN6

Other Functions

Function Pin

Ground 30

Input Function MyRio Inputs

System Start C/DIO0

System Stop C/DIO1

Emergency Stop C/DIO2

Reset C/DIO6

Fault 1 C/DIO4

Fault 2 C/DIO5

Fault 3 C/DIO3

Fault 1 Signal A/DI04 Pin 19

Fault 2 Signal A/DI013 Pin 26

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Appendix D Drawing of the Circuits

Drawing No. Title

1 Switchboard Equipment Layout

2 Push Button Inputs to Myrio

3 Motor Control Circuit

4 Motor Control Circuit Part 2

5 SSR Terminal

6 Myrio Terminal

7 VT’s Circuit Power Diagram

8 Current Input Connection

65

Drawing 1 Switchboard Equipment Layout

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Drawing 2: Push Button Inputs to Myrio

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Drawing 3: Motor Control Circuit

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Drawing 4: Motor Control Circuit Part 2

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Drawing 5: SSR Terminal

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Drawing 6: Myrio Terminal

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Drawing 7: VT’s Circuit Power Diagram

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Drawing 8: Current Input Connection

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Drawing 9: Motor Fault Circuit Schematic Wiring Diagram