Microcontroller Based 3 Phase Negative Phase Sequence Indicator

Microcontroller Based 3 Phase Negative Phase Sequence Indicator

Thesis Submitted By:

Anwarul Islam Sifat

Badhon Kumar Biswas

Ferdaous Zaman

Md. Jakaria Hossain

Supervised By:

Md. Minarul IslamSenior LecturerDept. of EEEStamford University Bangladesh

OUTLINES

• Concept of poly-phase System • Negative sequence component: Reason and Effect• Previous work and documentation• MCU based phase sequence indicator device• Simulation and Results

Concept of Poly Phase System

PHASE

Phase denotes the particular point in the cycle of a waveform, measured as an

angle in degrees.

It is normally not an audible characteristic of a signal.

It is a very important factor in the interaction of one wave with another, either

acoustically or electronically.

CONCEPT OF POLY PHASE SYSTEM

A poly-phase system is a means of

distributing electrical current.

Poly-phase systems have three or more

energized electrical conductors carrying

alternating currents with a definite time

offset between the voltage waves in each

conductor.

Poly-phase systems are particularly useful

for transmitting power to poly-phase load.

Poly Phase SystemCONCEPT OF POLY-PHASE SYSTEM

Three Phase System

It is a type of Poly-phase system and is the most common method used by electrical grids worldwide to transfer power.

It is also used to power large motors and other heavy loads.

A three-phase system is usually more economical.

CONCEPT OF POLY-PHASE SYSTEM

Phase Sequence

Phase sequence is defined as the order in which the three generated electrical voltages or currents rotate.

Each voltage is separated from the next generated voltage by 120 degrees.

Subscript identification to the voltages is as follows: Blue = B, Yellow = Y and Red = R

Types of Phase Sequence

From the figure, ABC sequence if we start from B then we can see that BCA is nothing but the same ABC sequence.

Similarly BAC and CBA sequence are the same as ACB, only we started from other phase.

So, a 3 phase system has only two possible sequence; i.e. ABC or ACB

Fortescue has formulated that any unbalanced system can be split up into a series of balanced systems.

Positive Sequence: It consists of 3 phasors equal in magnitude, displaced from each other by 120 degree in phase having same phase sequence as original phasors.

Negative Sequence: It consists of 3 phasors equal in magnitude, displaced from each other by 120 degree in phase having same phase sequence opposite to that of original phasors.

Phase Sequence Components

Zero Sequence: It consists of 3 phasors equal in magnitude and with zero phase displacement from each other.

It is to be noted that the original unbalanced system effectively has 3 complex unknown quantities A, B and C (magnitude and phase angle of each is independent).

It is also to be noted that each of the balanced components have only one independent complex unknown each, as the others can be written by symmetry.

A can be obtained by the phasor addition of A0, A1 and A2. Similarly B and C. Thus

A = A0 + A1 + A2B = B0 + B1 + B2C = C0 + C1 + C2we can define a new complex operator α

which has a magnitude of unity and when operated on any complex number rotates it anti-clockwise by an angle of 120 degree.

i.e. α = 1 120 = - 0.500 + ∠ j 0.866

Extraction of Sequence Components

Let us again examine the sequence components of the unbalanced quantity.

We can express all the sequence components in terms of the quantities for A phase using the properties of rotation of 0, 120 or 240 degree. Thus

Extraction of Sequence Components

2

2

A = A0 + A1 + A2

B = A0 + α A1 + α A2

C = A0 + α A1 + α A2

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Negative Sequence Component

Reason & Effect

NEGATIVE SEQUENCE COMPONENT REASON & EFFECT

The negative sequence set is also balanced with three equal magnitude quantities at 120 degrees apart but with the phase rotation or sequence reversed or ACB.

The negative sequence set is also balanced with three equal magnitude quantities at 120 degrees apart but with the phase rotation or sequence reversed, or ACB.

Negative Sequence


When using symmetrical components to analyze unbalanced system operation and fault conditions, the negative sequence is generated by unbalance.

A balanced three-phase load or a bolted three-phase fault will be entirely positive sequence.

Unbalanced loads or asymmetric faults will reduce the proportion of positive sequence current and will produce negative sequence currents.

Reason of Negative Sequence


Reason of Unbalance

• Voltage unbalance in the feeder supply

• Single phasing

• Phase reversal


Voltage Unbalance; Bangladesh Prospective

In Bangladesh voltage unbalance is common incident. Every day, low voltage abrupt the supply which leads to load shedding. The supply voltage of Bangladesh is 200~214v where actual supply is 220v.

Some of the common reason of voltage unbalance in Bangladesh.


Unbalanced incoming utility supply.

Unequal transformers tap settings.

Large single phase distribution transformer on the system

Open phase on the primary of a 3 phase transformer on the distribution system.

Faults or grounds in the power transformer.

Open delta connected transformer banks.

A blown fuse on a 3 phase bank of power factor improvement capacitors.

Unequal impedance in conductors of power supply wiring.

Unbalanced distribution of single phase loads such as lighting.

Heavy reactive single phase loads such as welders.


Effect of Negative Sequence

The effect of unbalanced voltages on

poly-phase induction motors is

equivalent to the introduction of

‘negative sequence voltage' in

balanced voltages.

NEGATIVE SEQUENCE COMPONENT REASON & EFFECT3 phase motor

The stator of an induction motor consists of a number of overlapping windings offset by an electrical angle of 120°.

When the primary winding or stator is connected to a three phase alternating current supply, it establishes a rotating magnetic field which rotates at a synchronous speed.

The direction of rotation of the motor depends on the phase sequence of supply lines, and the order in which these lines are connected to the stator.

Thus interchanging the connection of any two primary terminals to the supply will reverse the direction of rotation.


Negative sequence voltage produces in the air gap a flux rotating against the rotation of the rotor, tending to produce high current. A small negative sequence voltage may produce in the windings currents considerably in excess of those present under balanced voltage conditions.

An approximate 3.5 percent voltage unbalance will cause an approximate 25 per cent increase in temperature rise.

Temperature rise in motor

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Previous Work & Documentation

PREVIOUS WORK & DOCUMENTATION8085/8051

Microcontroller Based Phase Detection System

PREVIOUS WORK & DOCUMENTATION

Primary sides of three 230 / 6 volt potential transformers (PTs) are connected with individual phase and neutral of three-phase ac supply

Scaled down sinusoidal voltage signals from secondary side of each PT are fed into three isolated zero crossing detectors (ZCDs).

Three rectangular wave signals (R., Y. and B.) generated by three ZCDs are applied to three mono-stable multi-vibrators (MVs) for triggering at leading edge of rectangular wave signal

Output signals (R., Y. and B.) from three ZCDs are fed to three input port lines (P0, P1 and P2) of microprocessor / microcontroller.

Three output port lines (P3, P4 and P5) are connected with three LED circuits, L1, L2 and L3, respectively.

3-phase AC supply 50Hz is fed through voltage drop

arrangement duly stabilized by zener diodes to a

logic circuit comprising of NAND gates and OR

gates to detect the proper sequence of RYB by

series of pulses of fixed duration.

In the event of changing the sequence from RYB to

say YBR, the combination of NAND and OR gates

develops an output with a missing pulse during the

fixed time duration.


555 Timer Based Phase Sequence Detector


The missing pulse is used in

triggering a mono-stable 555

timer.

Thus, while the sequence is not

there the triggering to the timer is

missed which is indicated by an

LED driven from the output of the

555 timer.

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

LED_CTRL LED Control Output:

The LED_CTRL signal multiplexes the indication of phase drop, phase sequence error, and per phase reverse power on the LED_A, LED_B, and LED_C pins.

LED_A Phase A Phase Monitor Output: LEDs are connected to this pin to indicate phase drop or reverse power on Phase A

REVP:

This logic output goes logic high when negative power is detected on the sum of the three phase powers. This output is not latched and resets when positive power is once again detected .

LED_C Phase C Phase Monitor Output:

LEDs are connected to this pin to indicate phase drop or reverse power on Phase C

LED_B Phase B Phase Monitor Output: LEDs are connected to this pin to indicate phase drop or reverse power on Phase B

PREVIOUS WORK & DOCUMENTATIONPoly-phase metering IC

The ADE7762 detects the zero crossing of each phase.

A phase sequence error occurs when the sequence A>B>C>A> … is violated.

If a phase sequence error occurs, the Phase Seq/Drop LEDs blink at 1 Hz


Advantage of this design:

Easy to implement

Operation & Control is easy

No need to learn additional programming language

High accuracy output

Constrains:

The IC based phase detection system is the cheapest device to detect phase sequence. It consists of simple logic IC, rectifier circuit and led indication. The diversity of this device is very limited. Further work or development is not possible here.


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PIC Microcontroller BasedNegative Phase Sequence

Detector

Feature Project

FEATURE PROJECT

The proposed system for detecting negative phase sequence has some different methodology it based on the timing response of each phase.

A micro controller is used in this method to check the every phase in assigned time interval and detect which peak voltage response first.

Methodology

Logic was developed based on the response of peak voltage i.e. A, B and C.

In the programing code condition are applied to detect different combination of positive sequence.

By detecting positive sequence every other combination are assigned to negative sequence.

FEATURE PROJECT

Feature of PIC MCU4 MHz - 10 MHz osc./clock input

with PLL

3 Timer module: 8-bit/16-bit timer/counter with 8/16-bit programmable pre-scaler

Fast sampling rate

Wide operating voltage range (2.0V to 5.5V)

Low power consumption:- < 1.6 mA typical @ 5V, 4

FEATURE PROJECT

The Analog-to-Digital (A/D) converter module has five inputs for the PIC18F452 This module has the ADCON0 and ADCON1 register definitions that are compatible with the mid-range A/D module.

The A/D allows conversion of an analog input signal to a corresponding 10-bit digital number. • A/D Result High Register (ADRESH)• A/D Result Low Register (ADRESL)• A/D Control Register 0 (ADCON0)• A/D Control Register 1 (ADCON1)

10bit A/D Module

FEATURE PROJECT

Design Procedure

FEATURE PROJECT

Programming Flow chart

The sampling rate of 2800 samples per second facilitates the tester to work with both 50 and 60 Hz.

The program code can be reconfigured to make the working frequency flexible for a range from 1 to 1400 Hz by either increasing the sample size or by changing the program to sample and analyze at the same time

FEATURE PROJECT

In a summary:

To set up the logic to detect negative sequence, PIC18f452 ADC module must be initialized.

As 3 consecutive rising voltages is there to detect so 3 analog pin is assigned for ADC.

The maximum voltage or reference voltage is selected in this case it is +1.3v ~ -1v.

In the test sequence parameter every rising voltage is measured after 5ms delay.

The sampling rate of the signal is 100HZ according to Nyquist rate.

The phase sequence is tested by 3 phase function Phase12(); Phase23(); Phase31();

Each phase is assigned by appropriate flag memory.

The test sequence functions are executing under an infinite loop. LED is assigned according to flag output.

To detect the 3 phase sequence i.e. ABC or ACB

The 3 phase sequence is split into 3 different sequence i.e.Phase AB;Phase BC;Phase CA;

Here AB sequence is assigned to FLAG 1 Here BC sequence is assigned to FLAG 2 Here CA sequence is assigned to FLAG 3

Here AB sequence is assigned to port AN0 & AN1 Here BC sequence is assigned to port AN1 & AN4 Here CA sequence is assigned to port AN4 & AN1

Programming Logic ExplanationFEATURE PROJECT

Let consider for AB sequence,

Between this two sequence AN0 port have the1st peak value, then AN1 have the second peak value

Consider,

AN0 = FLAG1 = 1AN1 = FLAG1 = 0

FEATURE PROJECT

Let consider for BC sequence,

Between this two sequence AN1port have the1st peak value, then AN4 have the second peak value

Consider,


FEATURE PROJECT

Let consider for CA sequence,

Between this two sequence AN4 port have the1st peak value, then AN0 have the second peak value

Consider,


FEATURE PROJECT

Now if we want to check ABC sequence the logic will be implemented as follows

if(flag1==1&&flag2==1&&flag3==1) PORTDbits.RD7=1; //Phase ABC indicator LED

Above logic will check ABC sequence; except this all othercondition is negative phase sequence

Positive sequence i.e. BCA & CAB can be implemented same as above.

FEATURE PROJECT

if(flag1==1&&flag2==1&&flag3==1) PORTD.RD7=1; //phase ABC else if(flag1==0&&flag2==1&&flag3==1) PORTD.RD7=1; //phase CAB else if(flag1==1&&flag2==0&&flag3==1) PORTD.RD7=1; //phase BCAelse PORTD.RD6=1; // PHASE ACB

CODES of logic

FEATURE PROJECT

FEATURE PROJECT

SIM

ULA

TIO

N

Circuit components:

3 phase supplyResistor 1M, 100K, 10KDiodes D1N4002

FEATURE PROJECT

3 phase supply

FEATURE PROJECT

Voltage divider circuit output

FEATURE PROJECTRESULT

The positive sequence 3 phase signal.

The positive sequence indicator LED.

The negative sequence 3 phase signal.

The Negative Sequence Indicator LED.

FEATURE PROJECT

Thank You

Engineering

Microcontroller Based 3 Phase Negative Phase Sequence Indicator