© 2012, Siemens Industry Inc., all rights reserved
2012-2013 Distribution Systems Engineering Course for Con Edison
Course 1 –
Power Distribution Systems
& Power Circuit Analysis
Volume 1 –
Sessions 1-4, Tabs 0-10
2012
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General Outline
# Topic # sessions1 Power Distribution Systems & Circuit Analysis 82 Overhead Transmission Line Design 23 Environmental Effects of Distribution Lines 14 Overhead Distribution Line Design 35 Underground Cable Systems 16 Short Circuit Calculation on Radial Feeders 37 Protection & Coordination 18 Substation Design 39 Distribution System Losses 210 Economic Factors 211 Distribution System Grounding 112 Distribution Transformer Applications 313 Network Systems: Low-Voltage Grid, Spot, Primary 514 Lightning & Surge Protection 215 Distribution Planning & Reliability 216 DG & Emerging Technologies 3
Course
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Course 1 -
Session 1
Introduction to the Course
Procedures & Schedule
Instructors
General Course Outline
Very brief look at the History of Electricity
Overview of Power Systems
Overview of Distribution Systems
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Course 1 -
Session 2
Some Basic Relationships and Electrical Formulas
Overview of Power Distribution System Equipment
Distribution Secondary Systems
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Course 1 -
Session 3
Electrical Theory I
Math Review I
Math Review II
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Course 1 -
Session 4
Electrical Theory I
Three-Phase Power Systems
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Course 1 -
Session 5
Electric Power Concepts
Transformers
Motors
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Course 1 -
Session 6
The Per Unit System
One-Line Diagrams
Fault Analysis
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Course 1 -
Session 7
Energy & Loads
Introduction to Power Quality & Reliability
Voltage Unbalance, Flicker and Transients
Harmonics, Notching and Noise
Voltage Sags, Swells and Short Interruptions
Dealing with PQ Problems
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Course 1 -
Session 8
Application of Shunt Capacitors on Distribution Systems
Energizing Transients
Reactive Power Conventions
Power Factor Correction
Released Capacity
Power Loss and Energy Loss Reduction
Feeders with Lumped Loads and Uniformly Distributed Loads
Sizing and Locating to Minimize Power and Energy Losses
Voltage Control of Distribution Systems
Calculation of Voltage Drop
Voltage Unbalance and Effect of Voltage Magnitude on Performance
Voltage Regulators and Line Drop Compensation
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Course 2, Overhead Transmission Line Design (2 sessions)
Line Components Overview
Conductors
Towers
Insulators and Hardware
Electric and Magnetic Fields
Insulation Coordination
Line Uprating
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Course 3, Environmental Effects of Distribution Lines (1 session)
Environmental Effects of Electric and Magnetic Fields
Update on Health Effects of Electric and Magnetic Fields
Radio and Television Interference from Distribution Lines
Magnetic Field Management
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Course 4, Overhead Distribution Line Design (3 sessions)
Line Design Overview
Line Design Criteria
National Electric Safety Code
Clearances requirements
Components of Overhead Distribution Lines
Catenaries –
Sag and Tension Calculations
Construction Types
Pole and Guy Wire Selection and Calculations
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Course 5, Underground Cable Systems (1 session)
Cable types
Terminations
Splices
URD system components
Duct banks
Manholes & vaults
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Course 6, Short Circuit Calculations on Radial Feeders (3 sessions)
Calculation of Feeder Impedances
Basic Concepts
Single-Phase Circuits
Systems with Multiple Wires Per Phase
Three-Phase OH Lines and Cable Circuits
Fault Current Asymmetry
Short Circuit Current Calculations
Simplified Relationships for Radial Systems
Source Impedances
Balanced 3-Phase Faults
Unbalance Faults in Three-Phase Circuits
Maximum Current Criteria
Fault Current Profile Curves
Arcing Faults
Example Calculations
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Course 7, Protection & Coordination (1 session)
Over-current protection devices
Relays
Circuit Breakers
Circuit Switchers
Reclosers
Sectionalizers
Switches
Fuses
Over-current protection practices
Time/current curves
Through fault protection of transformers
Coordination of over-current devices
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Course 8, Substation Design (3 sessions)
Bus Configurations
General Design Parameters
Rigid & Strain Buses
Protective Relaying
Electrical Clearances
Grounding
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Course 9, Distribution System Losses (2 sessions)
Overview of distribution system losses
Fundamental principles and economic considerations
Load factor and Loss factors
Peak responsibility factor
Transformer losses
Transformer model for losses
No Load (Core) Losses
Load (I2R) Losses
Load and loss factors
Line losses
Uniformly distributed load on line
Reducing line losses with capacitors
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Course 10, Economic Factors (2 sessions)
Basis for utility financing
PURPA
PUHCA
Time value of money
Annual carrying charges
Definition of economic terms
Economic evaluations
Present worth analysis
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Reasons For System Grounding
Criteria for Classification of System Grounding
Ungrounded (Delta) Systems
Creating a Grounded System
High-Resistance Grounding
Multi-Grounded Neutral Systems
Sequence Impedance Ratios
Fault Current Profiles
Unfaulted
Phase Voltages
Grounding of Combination Feeders (Network & Non-Network)
High Reactance Grounding of Sub-Transmission Systems
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Course 11, Distribution System Grounding (1 session)
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Course 12, Distribution Transformer Applications (3 sessions)
Primary Systems and Secondary Services
Permissible Connections and Connections to Avoid
Single-Phase Pole-Top Transformers
Cable-Fed Transformer Characteristic Comparison
Secondary Fault currents
Delta-Delta Bank Application Concerns
Ungrounded Secondary System Voltages
Open-Wye
Open-Delta Bank Application Concerns
Floating-Wye
Delta Bank Switching Voltages Under Load
Tank Heating in 3-Phase Transformers
Ferroresonance
Considerations
Transformer Loading for 4-Wire Delta Service
Voltage Unbalance in 4-Wire Delta Service
Single-Phase Unit Overcurrent
Protection Considerations
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Course 13, Network Systems: Low- Voltage Grid, Spot, Primary (5 sessions)
Fundamentals of Design and Operation
Supply Substation Configurations
Primary Feeder Grounding and Relaying
Network Protector Fuses, Cable Limiters, and Coordination
Backfeed
Current to Primary Feeder Faults –
Neutral Conductor Overheating
Network Protector Relaying: Electro-Mechanical and Microprocessor
Reverse Current Sensitivity Requirements
Basis for Relay Close Settings
Overvoltages
in Secondary During Capacitive Backfeed
Fundamentals of Magnetic Field & Mitigation Measures
Non-Dedicated Feeder Spot Network Applications
Supplemental Protection Schemes for 480-Volt Spot Networks
Closed-Transition Transfers & Co-Generation on Spot Networks
Network Primary Feeder Impedance Calculation Program
Low-Voltage Spot Network Simulator
Primary Voltage Networks
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Course 14, Lightning & Surge Protection (2 sessions)
Lightning Surges
Surge arresters
Insulation Coordination
Overvoltage Protection of overhead lines
Overvoltage Protection of underground cables
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Course 15, Distribution System Planning & Reliability (2 sessions)
Performance Assessment and Objectives
System Expansion Criteria
Multi-objective Analysis
Total Service Quality
Factors Affecting Reliability
Historical and Predictive Reliability Analysis
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Course 16, Distributed Generation & Emerging Technologies (3 sessions)
Regulatory, Commercial, and Economic Issues
Distributed generation technologies•
Co-generators (Combined Electric & Steam)•
Fuel Cells•
Wind Turbines•
Photovoltaics•
Solar Thermal Electric•
Small-scale Hydro•
Battery Energy Storage
System impact of distributed generation •
Advantages & Disadvantages of Distributed Generation•
Energy Conversion Efficiencies•
Discussion of Successful Installations•
Interconnection Transformer Connections and System Grounding•
Relaying and Protection Issues•
Voltage and Power Quality Considerations
© 2012, Siemens Industry Inc., all rights reserved
Tab 1 -
A Brief History of Electricity Distribution Systems Engineering –
Course 1
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Where did it start?
Electricity has been around as long as the Earth itself.
It is theorized that the severe electrical storms (lightning) played a significant role in the creation of life on this planet which is
a few billion years old
The difference it has made to our lives today has a much shorter
history, relative to the age of the Earth
Not the cave man days but still pretty far back
Somewhere along the way someone found rocks that are natural magnets which are a type of iron ore now known as
Magnetite
The rocks were believed to have great powers which ranged from curing many ailments to attracting lovers
•
Magnets are still thought to have therapeutic effects
Around 376 BC the simple compass was used in China•
The main reason was for troop movements
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Skip to the Seventh Century
A Greek philosopher and mathematician by the name of Thales in the late seventh century noticed that by rubbing the stone amber on a cloth, the stone would attract light
objects
He believed that the amber became magnetic•
But it did not attract the same objects that were attracted by the magnetite
•
The concept was left alone and not revisited for awhile
By the thirteenth century, the compass was being used aboard ships for navigation
The Chinese were the first to use the device
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A Little Bit Further in Time
There was still the issue with the amber and the cloth
Was it really a magnet?
In England, a physician, William Gilbert, published a book about
magnetic theory in 1600•
His theory was that the attraction of small items to the amber was not due to magnetism, rather it was due to a force he called “Electrica”
which is derived from the Latin and Greek words for amber
•
Others are intrigued by his theory
Otto Von Guericke
In 1660, he creates a static electricity generator
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Some People to Remember
Francis Hauksbee
In 1709, he discovered that by putting a small amount of Mercury
in the glass of Von Guerick's generator and evacuating the air from it, when a charge was built up on the ball and his hand placed onto it, it would glow. This is similar to the phenomenon
known as St. Elmo's Fire. He did not know it then but he actually invented the neon light
Charles Dufey
Around 1733, he discovered that statically charged materials would react like magnets; either attracting or repelling each other. He deduced that there were two types of electricity.
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Some People to Remember (continued)
Benjamin Franklin
Best known for his kite flying in 1752•
Similar experiment killed a Russian scientist!
He referred to the two types electricity stated by Duffy as positive and negative
James Watt
Not really involved in electricity but he came forth with the idea that steam engines would replace horses
Derived the force exerted by horses•
Horse power –
lifting a known weight an exact distance in a specific interval
•
The term ‘watt’
is named after him
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Some People to Remember (continued)
Alessandro Volta
Along with Luigi Galvani proved that when certain metals and chemicals come into contact with each other they can produce an electrical current •
Which leads to a battery and the term ‘volt’•
And eventually, the galvanizing process
Hans Christian Oersted
In 1820, using a battery, noticed that a current of electricity would cause a deflection on a compass needle. From this observation Oersted introduced the world to electromagnetism.
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Some People to Remember (continued)
Andre Marie Ampere
Discovered that two parallel current wires will repel or attract
each other depending on the current flows through the wires (in the same or in opposite direction)
The ampere, the unit of electric current, is named after him
Humphrey Davy
In 1821
shows that direct current is carried throughout the volume of a conductor. He discovers that resistance is increased
as the temperature rises
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Some People to Remember (continued)
Thomas Seebeck
He discovered ‘thermal electricity’•
Twisted two dissimilar wires together, applying heat and generated a small current flow
•
Thermocouple technology is used in pilot lights
Georg Simon Ohm
In 1826 establishes Ohm's law, V=IR, the idea of voltage as the
driver of electric current. •
Simple concept but VERY significant
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The Turning Point –
Pun Intended
Michael Faraday (1791-1867)
Discovered electromagnetic induction
In 1831 he performed two simple but major experiments. •
In his first experiment he placed two separate coils of wire around an iron ring. He found that by passing electricity through one of the coils of wire the magnetic effect in the coil passes through the
iron ring to the second coil and produced electricity in the second coil. He created the first ‘transformer’.
•
His second experiment proved that passing a magnet through a coil of wire created (generated) electricity. The generator is discovered.
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Siemens Industry Inc., Siemens Power Technologies International 1-11
Maxwell’s Equations
James Maxwell (1831-1879)
Maxwell was one of the finest mathematicians in history. His contribution to the world of science is considered equal to Albert Einstein and Sir Isaac Newton. He translated Faraday's theories concerning magnetism into mathematical expressions. The electromagnetic unit of measure for magnetic flux, a maxwell, is
named in his honor.
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Some of the First Generating Plants
Glasgow, England, circa 1878
Football game played under lights
Pearl Street , New York circa 1881
Thomas Edison’s first ‘real’
power station
Godalming, England, 1881
A hydro driven dynamo at Westbrook Mills supplied the power for the world's first public electricity supply system, which supplied the lighting for the streets
•
Lasted only a couple of years
New York City, USA, 1882
In January, Thomas Edison, opened 'Edison Electric Light Station' at No. 57 Holborn Viaduct (Steam driven dynamo)
Brighton, England, 1882
In February, the Hammond Electric Light Company opens a generation station
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More about Thomas Edison
He was issued over 1090 patents
The light bulb paves the way for the electric street lighting
During the years between 1880-1887, he improved greatly upon his electric light, heat, and power systems. He applied for and received over three hundred patents, many of which were of extraordinary and fundamental importance to electric power and a ‘three wire’
generation and feeder system.
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Siemens Industry Inc., Siemens Power Technologies International 1-14
Today
Electricity has become essential to our world
Lighting
Heat
Food •
Storage•
Preparation
Entertainment
Communication
And…..•
There will be new ways we have not thought yet
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Recap
Magnets were discovered
Static electricity was discovered
Relationship between metals allowed the creation of the battery
Direct relationship between volts, resistance and current developed
Faraday discovered the transformer and the generator
Maxwell explain the findings mathematically
Edison gave us a reason to use electricity
© 2012, Siemens Industry Inc., all rights reserved
Tab 2 -
Overview of Power Systems Distribution Systems Engineering –
Course 1
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Siemens Industry Inc., Siemens Power Technologies International 2-2
Work and Energy
Energy
is the capacity for doing Work
in a physical
system in changing from its actual state to a another state (units of energy
and work
are the same)
-
Power
is the time rate at which energy
is supplied, or the time rate at which
work
is done
-
Mechanical
work
in pushing a box over a flat surface
International System of units (SI)
ENERGY = WORK TO CHANGE STATE
FORCE
DISTANCE
FORCE
FORCE x DISTANCE = NEWTON x METER = JOULEWORK =
POWER = ENERGY / TIME = JOULE / SECOND = WATTD#3, CE SC 2011, WORK DEFINITION MECHANICAL.FCW
State 1 State 2
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Work and Energy
Energy
can not be created or destroyed
-
Energy appears in many forms, classified broadly as mechanical, thermal, electrical, chemical, and nuclear. Mechanical energy is either kinetic (energy of motion) or potential (energy of position)
-
Energy can be transformed from one form to another: mechanical to electrical (generator), electrical to mechanical (motor, solenoid), electrical to heat (clothes dryer), electrical to light (incandescent light
bulb), chemical to electrical (battery)
Purpose of the electric power system is to transfer energy
from the sources or energy to the locations
where work
can be done
Energy
is transferred electrically from one location to
another through transmission lines, transformers, primary distribution lines, secondary circuits, services-
Transferring energy electrically requires an electro-motive force (voltage difference) and a path (electrical conductors)
Siemens Industry Inc., Siemens Power Technologies International 2-3
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Siemens Industry Inc., Siemens Power Technologies International 2-4
Components of the Typical Utility Power System For Energy Transportation
GEN
GEN
TRANSMISSION SYSTEMPOWERPLANT
N.O.
DISTRIBUTIONSUBSTATION
POWER PLANTSUBSTATION
TRANSMISSIONSUBSTATION
DISTRIBTION PRIMARYFEEDER
DISTRIBUTIONTRANSFORMER
SUB-TRANSMISSION
MET
ERS
SERV
ICES
MAI
N BR
EAKE
R
BRAN
CH B
REAK
ERS
CONSUMERWIRING
SECO
NDAR
Y
GENERATORSTEP-UP
TRANSFORMER
CE 2008,D#1,TYPICAL UTILITY POWER SYSTEM.FCW DISTRIBUTION SECONDARYDistribution transformers supply energy at the utilization voltage level. Today, distributed energy sources are being added to the distribution primary and secondary
systems.
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Siemens Industry Inc., Siemens Power Technologies International 2-5
Simplified diagram
The diagram below illustrates how energy gets from the central generating station to the consumer to do work
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World-Wide Energy Sources For Generating Electricity
Siemens Industry Inc., Siemens Power Technologies International 2-6
Energy Source Average Electric Power (GW)
Proportion(%)
Coal 942.6 41Oil 126.7 5
Natural Gas 490.7 21Nuclear 311.6 13Hydro 375.1 16Other 64.8 3Total 2311.4 100
Data for year 2008, from International Energy Agency
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Siemens Industry Inc., Siemens Power Technologies International 2-7
Conversion of Mechanical Energy to Electrical Energy
Mechanical energy is converted to electrical energy
by a magnetic field produced on the generator rotor that induces sinusoidal voltages into the electric coils (windings) on the generator stator
Mechanical sources for rotating the generator rotor•
Steam Turbine, Water Turbine•
Gas Turbine, Wind Turbine
MAIN EXCITER2400 kW, 400 V
N
S
COMMUTATOR
SLIP RINGS
PILOTEXCITER
25 KW
N
S
STATOR
STATOR
3-PHASE STATOR WINDINGS
ABC
GENERATORLEADS TOISOLATED PHASE BUS
MECHANICALPOWER INPUTFROM PRIMEMOVER
3-PHASE ALTERNATOR500 MW, 23 KV, 60 HZ
ROTOR
6000 A
D#3, CE 2011 SC, SYN GEN SIMPLIFIED.FCW
GENERATORROTOR
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Siemens Industry Inc., Siemens Power Technologies International 2-8
Steam Turbines Produce > 50% of Electricity Steam Production -
Basics
Fuel (usually fossil fuels) is consumed to create steam from water
Coal, Oil, and Natural Gas are the primary fuels •
Some 70 % of the Electricity generated in the US is from fossil fuel
Nuclear fuel is also used to create steam
Two types of steam plants
High Pressure (3600 rpm) -
Coal, Oil, Natural Gas
Low Pressure (1800 rpm) -
Nuclear
The steam is forced into the turbine blades
This causes rotation of the turbine shaft to which the blades are attached, and rotates the generator rotor attached to the turbine shaft
Steam exiting turbine is recovered (condensed to water) and sent through the process all over again
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Power Plant With Steam Turbine Driven Generator
Siemens Industry Inc., Siemens Power Technologies International 2-9
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Siemens Industry Inc., Siemens Power Technologies International 2-10
Hydro Electric Production
Water is forced across the blades of a hydraulic turbine
First plants started out as milling or textile machine plants and were converted to plants for generating electricity.
Requires a pressure differential which is created by the height of the water source above the hydraulic turbine.
Large plants require large sources of water
•
Best known example in the US is the Hoover Dam
•
Pumped storage hydro used for peaking: pump to upper pond off peak, discharge to lower pond at time of peak
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Siemens Industry Inc., Siemens Power Technologies International 2-11
Hydro Electric Production
HYDRO ELECTRIC GENERATORS ROTATE AT MUCH LOWER SPEED THAN GENERATORS POWERED WITH STEAM TURBINES AND GAS TURBINES.
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Hydro Electric Production
Siemens Industry Inc., Siemens Power Technologies International 2-12
• SMALL HYDRO ELECTRIC PLANT IN CENTRAL PA ON RAYSTOWN DAM• ALLEGHENY ELECTRIC COOPERATIVE• ONE 7 MW AND ONE 14 MW MACHINE GENERATING @ 6900 VOLTS• TRANSMITS AT 46 KV TO RURAL SUBSTATIONS
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Siemens Industry Inc., Siemens Power Technologies International 2-13
Wind Turbine Production
Wind mills have been around for centuries
Generator rotor turned by energy extracted from wind
Turbine blades are similar to airfoils on an airplane, producing torque from flow of wind
Viewed as a ‘green’
energy source
Output is proportional to the velocity of the wind
Large wind farms being built today in USA
•
Shepherds Flat Wind Farm in Oregon
30 square mile area
Completion date 2013
338 2500 kW turbines
Total capacity of 845 MW•
Many require reinforcement of transmission system due to remoteness from load centers
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Solar Panels, Photo Voltaic
Siemens Industry Inc., Siemens Power Technologies International 2-14
• Solar panels generate dc voltage• Inverters convert dc to ac• Small systems interface to low-voltage distribution system (1ϕ
or 3ϕ)
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Siemens Industry Inc., Siemens Power Technologies International 2-15
The Gas Turbine
The concept is to rotate the turbine rotor to which an electrical generator is coupled
In a gas turbine, a pressurized gas reacts with the turbine blades and spins the turbine rotor to which blades are attached. In all modern gas turbine engines, pressurized gas is produced by burning a fuel such as propane, natural gas, kerosene or jet fuel. The heat that comes from burning the fuel expands the air, and the high-speed exhaust of this hot air spins the turbine.
The rotor of the gas turbine is attached to the rotor of the electric generator.
Gas turbines tend to use more fuel when idling, and it is preferred that a relatively constant, rather than a rapidly fluctuating, load be connected to it.
Gas turbines are sometimes used in combined cycle plants where the waste heat from the gas turbine is used to make steam
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Gas Turbine For Combined Cycle Power Plant
Siemens Industry Inc., Siemens Power Technologies International 2-16
COMPRESSORSECTION
COMBUSTIONCHAMBER
SHAFT FORCONNECTIONTO GENERATOR
TURBINESTAGE
EXHAUST
AIRINPUT
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Siemens Industry Inc., Siemens Power Technologies International 2-17
Nuclear Power Generation
Nuclear power plants provide about 17 percent of the world's electricity. Some countries depend more on nuclear power for electricity than others. In France, for instance, about 75 percent of the electricity is generated from nuclear power.
In the United States, nuclear power supplies about 15 percent of the electricity overall, but some states get more power from nuclear plants than others.
There are more than 700 commercial reactors (400 nuclear power plants) around the world, with more than 100 commercial reactors in the United States (at 65 plants).
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Siemens Industry Inc., Siemens Power Technologies International 2-18
The Next Step
Electric generator output Φ-to-Φ
voltage (pressure) is typically between 11 and 22 kV, depending on size
Generator electrical energy output is transported to the loads via a well defined path (electric conductors of lines, and electrical conductors and magnetic fields in transformers )
The generator output voltage is increased with a “generator step-up transformer”
at the generation plant to allow transportation of energy over long distances
This is referred to as stepping up the voltage
Transformer is connected delta on the generator side and grounded-wye on transmission side
The output voltage of the generator step-up transformer usually is the operating voltage of the transmission or subtransmission system
The power travels on the transmission system to the load centers
Often called the high tension wires
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Siemens Industry Inc., Siemens Power Technologies International 2-19
Generation Plant, Step-Up Transformers and Transmission Lines
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Siemens Industry Inc., Siemens Power Technologies International 2-20
Overhead Transmission Lines
Examples of transmission towers
Design is dependent upon voltage and surroundingsDOUBLE CIRCUIT 345 KVSTEEL LATICE TOWERS
SINGLE CIRCUIT 345 KVWOOD “H”
FRAME TOWERS
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Cables For HV Power Transmission
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THREE-PHASE OIL-FILLEDPIPE-TYPE CABLE
SINGLE-CONDUCTOR SOLIDDIELECTRIC POWE CABLE
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Siemens Industry Inc., Siemens Power Technologies International 2-22
Transmission to Distribution
Another substation with a step-down transformer reduces the voltage of the transmission / sub-
transmission system to the voltage level of the primary distribution system
The primary distribution lines (feeders) travel along the streets to supply customers from the secondary side of distribution transformers
Distribution transformers lower the primary distribution voltage down to utilization voltage levels.
STEP-DOWN TRANSFORMER, 115 KV TO 12.5 KV
UNDERGROUND EXITS FOR PRIMARY DISTRIBUTION FEEDERS,(VOLTAGES BETWEEN 2.4 KV UPTO 34.5 KV)
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Siemens Industry Inc., Siemens Power Technologies International 2-23
Distribution Primary Lines
Operate typically around 15kV
Although 2.4 kV through and 34.5kV are used
Overhead or underground does not matter in the fundamentals
The purpose is to get the power from the distribution substation to the end user
Primary lines emanating substation are three phase
Single-phase primary lines are run to loads that require only 1-
phase service
THREE-PHASEPRIMARY LINES
SINGLE-PHASE PRIMARY LINE(ONE Φ
WIRE & NEUTRAL WIREIN MGN SYSTEM, TWO Φ
WIRESIN A 3-WIRE PRIMARY SYSTEM) RESIDENTIAL
LOADSREQUIRING ONLYSINGLE-PHASESERVICE
THREE-PHASE LINEBETWEEN TWO DISTRIBUTIONSUBSTATIONS, OPERATED WITHA NORMALLY OPEN POINT
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Siemens Industry
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Types of Electric Distribution Utilities
Three major types
Investor Owned Utilities or IOU
•
They may own the generation right to the meter. In recent years, many have ‘unbundled’
and sold the generation.
•
They issue stock which can be preferred or common. Profits are used to make dividend payments for the share holders. The amount of profit is regulated as well as the costs incurred.
Municipal
•
They purchase power from the power producers. They may generate
their own power. Controlled by the local governing body. The electrical facilities are paid for through taxes and rates.
Co-operatives
•
Usually considered only Distribution Companies but many have generation capacity. Do not issue stocks and all profits are reinvested or used to reduce the rates.
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Recap
Mechanical energy converted to electrical energy at a generation
station
The output of the electrical generator is tied to the transmission system via a generator step-up transformer
The transmission system (138 kV or 345 kV at Con Ed) moves the electric energy to the load centers
Another substation (distribution/area substation) has a transformer(s) to reduce the transmission voltage to the distribution primary voltage level (4.16 kV, 13 kV, 27 kV, or 33 kV at Con Ed), and has buses to supply distribution primary feeders
Distribution system primary feeders run throughout the area were
customers are to be served
Other transformers (distribution transformers) convert the distribution primary voltage (4 kV to 34.5 kV) to utilization voltages supplied to customers ( 120/240 V 1ϕ
3W, 208Y/120 V 3ϕ
4W, 480Y/277 V 3ϕ
4W )
© 2012, Siemens Industry Inc., all rights reserved
Tab 3 - Overview and Introduction to Distribution Systems Distribution Systems Engineering –
Course 1
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Siemens Industry
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What is a distribution system?
Different types of distribution systems
Types of equipment
Low-voltage network system overview
Voltage and current ratings and wire configuration
Industry areas of focus
Topic Areas
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Siemens Industry
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Typical Utility Power System Generation, Transmission, Distribution
GEN
GEN
TRANSMISSION SYSTEMPOWERPLANT
N.O.
DISTRIBUTIONSUBSTATION
POWER PLANTSUBSTATION
TRANSMISSIONSUBSTATION
DISTRIBTION PRIMARYFEEDER
DISTRIBUTIONTRANSFORMER
SUB-TRANSMISSION
MET
ERS
SERV
ICES
MAI
N BR
EAKE
R
BRAN
CH B
REAK
ERS
CONSUMERWIRING
SECO
NDAR
Y
GENERATORSTEP-UP
TRANSFORMER
CE 2008,D#1,TYPICAL UTILITY POWER SYSTEM.FCW DISTRIBUTION SECONDARY
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Siemens Industry
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Transmission Systems
Interconnect the generation sites
Allow bulk power transfers between areas / regions
Operated independently of the Distribution Companies
Called Independent System Operator (ISO)•
New England (ISONE) and New York (NYISO) are examples
•
Coordinate generation and transmission across a wide geographic area, matching generation instantaneously to the demands for electricity
•
Forecast load and schedule generation to assure sufficient generation and backup power is available if plant or power line is lost
•
Coordinate generation and transmission to provide non-discriminatory access , facilitate competition between suppliers, and do regional planning
Typical Voltages
115 kV, 138 kV, 230 kV, 345 kV, 500 kV and higher•
Lower voltages such as 23 kV through 69 kV usually are considered sub transmission voltages (note that 23 & 34.5 kV also used for distribution)
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Siemens Industry
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Distribution Substations
Supplied from either transmission system or sub- transmission system
The distribution substation may or may not be owned and operated
by the Distribution Company
Typical high-side voltages are between 23 kV up to 230 kV
Larger distribution substations typically are supplied from higher voltage sub transmission lines / transmission lines (ie: 138 kV or 115 kV versus 23 kV or 34.5 kV)
Larger distribution substations typically are supplied from a larger number of transmission / sub-transmission lines
Distribution substation size is a function of:
Load density in area to be supplied
Area to be supplied from the distribution substation
Distribution primary voltage level (4.16 kV, 13.2 kV, 23 kV, 24.94 kV, 27 kV, 33 kV, 34.5 kV)
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Siemens Industry
Inc., Siemens Power Technologies International 3-6
An Example of a Distribution Substation Two Transmission Lines, Two Transformers
SUBSTATIONTRANFORMER21/28/35 MVA
Z = 10%
138 KV TRANS-MISSION LINE 1
138 KV TRANS-MISSION LINE 2
138 KV BUSES& BREAKERS
13.8 KV MEDIUMVOLTAGE BUSES
87
87
POTENTIAL XFR FOR RELAYING & METERING
52
CONTROLPOWER
TRANSFORMER 87
R
TRANSFORMER DIFFERENTIAL RELAY
FEEDER PHASE, GROUND, & RECLOSING RELAYS
52R
PRIMARY DISTRIBUTION FEEDER(UG, OH, COMBINATION)
52R
52R
52R
52R
52R 52 FEEDER CIRCUIT BREAKER
D#3, CE SC 2011, Dist Substation Two Xfrs-2.FCW
BUS TIE BREAKER EITHER N.O. OR N.C.
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Siemens Industry
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Area Substation for Supply to Low Voltage Networks
NWK.
1
NWK.
1NW
K. 2
NWK.
2
NWK.
1
NWK.
1NW
K. 2
NWK.
2
NWK.
1
NWK.
1NW
K. 2
NWK.
2
NWK.
1
NWK.
1NW
K. 2
NWK.
2
NWK.
1
NWK.
1NW
K. 2
NWK.
2
NWK.
1
NWK.
1NW
K. 2
NWK.
2
NWK.
1
NWK.
1NW
K. 2
NWK.
2
NWK.
1
NWK.
1NW
K. 2
NWK.
2
BUS SECT. 1N BUS SECT. 2N BUS SECT. 3N BUS SECT. 4N
BUS SECT. 1S BUS SECT. 2S BUS SECT. 3S BUS SECT. 4S
XFR. 1 XFR. 2 XFR. 3 XFR. 4
1 SYN. N 2 SYN. N 3 SYN. N 4 SYN. N
1 SYN. S 2 SYN. S 3 SYN. S 4 SYN. S
XFR. 5IN PLACE
SPARE
NORMALLYOPEN
NORMALLYOPEN
NORTH SYNCHRONIZING BUS
SOUTH SYNCHRONIZING BUS
13.8 KV 13.8 KV 13.8 KV 13.8 KV
1 XFR. N
1 XFR. S
2 XFR. N 3 XFR. N
3 XFR. S
4 XFR. N
4 XFR. S
138 KV 138 KV 138 KV
2 XFR. S
138 KV
• SUPPLY FOR TWO 16 FEEDER LV NETWORKS (Double contingency design)
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Siemens Industry Inc., Siemens Power Technologies International 3-8
Substations for Supply to Large LV Networks Outside View of Substations in Metropolitan Area
• SUB-STATION FACADE DESIGNED TO BLEND IN WITH SURROUNDING ARCHITECTURE
•TRANSFORMER / BUS ARRANGEMENT IN THESE SUBSTATIONS WOULD BE SIMILAR TO THAT SHOWN ON PREVIOUS SLIDE
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Siemens Industry Inc., Siemens Power Technologies International 3-9
Five Basic Distribution System Configurations
Radial
Primary Loop (automatic or manual operation)
Primary Selective
Secondary Selective
Primary Network (4 kV)
Low-Voltage (Secondary) Network (grid, spot, isolated spot)
RADIAL NETWORK
COST
SAIDISAIFI
D#3, CE SC 2011, System Cost-Reliability .FCW
CustomersNoTotal
onsInterruptiofNodInterrupteCustomersNoSAIFI.
.*.
CustomersNoTotaldInterrupteCustomersNoTotalSAIFI
..
CustomersofNoTotal
AffectedCustomersNoOutageofDurationSAIDI
..*
CustomersofNoTotalDurationsonInterruptiCustomer
SAIDI.
SAIFI = System Average Interruption Frequency Index
SAIDI = System Average Interruption Duration Index
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Siemens Industry Inc., Siemens Power Technologies International 3-10
SIMPLE LAYOUT
One way real power flow under normal conditions (exception is if distributed generation is on feeder)
Also used in transmission and sub-transmission systems
Note: var flow at any point in feeder can be in either direction (away from or towards the distribution substation)
Radial Distribution System
N.O.
DISTRIBUTIONSUBSTATION
CE 2008,D#1,RADIAL DISTRIBUTION CIRCUITS.FCW
RADIALCIRCUITMAIN LINE
REAL POWER FLOW
REAL POWER FLOW
SUB
TRAN
SMIS
SIO
N SU
PPLY
LIN
ES
SECONDARY AND SERVICES
N.C.
N.C.
N.O. = NORMALLY OPENN.C. = NORMALLY CLOSED
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Siemens Industry Inc., Siemens Power Technologies International 3-11
Main line 3Ø
Lateral taps -
3Ø, 2Ø, and/or 1Ø
R
Radial Distribution System (continued)RADIAL DISTRIBUTION CIRCUITS CONSIST OF:
-
MAIN LINES (THREE-PHASE CIRCUITS)-
LATERAL TAPS (BRANCHES) , EITHER THREE-PHASE, TWO-PHASE, OR SINGLE-PHASE
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Siemens Industry Inc., Siemens Power Technologies International 3-12
Primary Radial System (simplified to show operation)
• NORMAL CONFIGURATION, NO FAULT
DISTRIBUTION SUBSTATION
FEEDERBREAKER
DIST.TRANSF.
CIRCUITRECLOSER
LINEFUSES
MANUALSWITCH 1
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF
MANUALSWITCH 2
CLOSED CLOSED
D#3, 2012, Radial Syst Simplified Faults.FCW
138 KV 13 KV
DISTRIBUTION SUBSTATION
FEEDERBREAKER
DIST.TRANSF.
CIRCUITRECLOSER
LINEFUSES
MANUALSWITCH 1
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF
MANUALSWITCH 2
OPEN CLOSED
D#3, 2012, Radial Syst Simplified Faults-1.FCW
138 KV 13 KV
FAULT
• PERMANENT FAULT BETWEEN SWITCH 1 AND RECLOSER
1. All customers without service until fault repaired and feeder re-energized from substation.
2. Partial power returned until fault repaired by opening SWITCH1, and reclosing feeder breaker.
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Siemens Industry Inc., Siemens Power Technologies International 3-13
Primary Loop Distribution System
- Used on the mainline and on laterals of the distribution systems
- Looped distribution systems are operated in a radial fashion
- Systems can be automated to restore part of full service following fault (smart grid)
N.O.
DISTRIBUTIONSUBSTATION 1
CE 2008,D#1,LOOP DISTRIBUTION CIRCUITS.FCW
RADIALCIRCUITMAIN LINE
REAL POWER FLOW
REAL POWER FLOW
SUB
TRAN
SMIS
SIO
N SU
PPLY
LIN
ES
SECONDARY AND SERVICES
N.O.
N.O.
REAL POWER FLOW
REAL POWER FLOW
N.O.
N.O.
N.O.
DISTRIBUTIONSUBSTATION 2
DISTRIBUTIONSUBSTATION 3
P
P
N.O. = NORMALLY OPENN.C. = NORMALLY CLOSED
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Siemens Industry Inc., Siemens Power Technologies International 3-14
R
R
Main line 3Ø
Lateral taps -
3Ø, 2Ø, and/or 1Ø
CIRCUITS OPERATED IN A RADIAL FASHION
Primary Loop System (different substations)
SUBSTATION 1
SUBSTATION 2
N.O. NORMALLY OPEN POINT
N.0.
N.0.
N.0.
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Siemens Industry Inc., Siemens Power Technologies International 3-15
R
R
Main line 3ØLateral taps -
3Ø,
2Ø, and/or 1Ø
CIRCUITS OPERATED IN A RADIAL FASHION
Primary Loop System (same substation)
SUBSTATION 1
N.O. NORMALLY OPEN POINT
N.0.
N.0.
N.0.
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Primary Loop System (simplified to show operation)
Siemens Industry Inc., Siemens Power Technologies International 3-16
• NORMAL CONFIGURATION, NO FAULT1.
Feeder 1 & Feeder 2 operate in radial fashion
2. Tie switch between Feeders 1 & 2 normally open
3. Tie switch can be manually operated or remotely operated via automation scheme
DISTRIBUTION SUBSTATION 2
FEEDERBREAKER
DIST.TRANSF.
CIRCUITRECLOSER
LINEFUSES
MANUALSWITCH 1
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF
MANUALSWITCH 2
CLOSED CLOSED
D#3, 2012, Loop Syst Simplified Faults.FCW
138 KV 13 KV
FEEDERBREAKER
DIST.TRANS 1
CIRCUITRECLOSER
LINEFUSES
MANUALSWITCH 1
DIST.TRANS 2
DIST.TRANS 3
DIST.TRANS 4
DIST.TRANS 5
DIST.TRANS 6
DIST.TRANS 7
DIST.TRANS 8
MANUALSWITCH 2
CLOSED CLOSED
DISTRIBUTION SUBSTATION 1
TIE SWITCH (TS)NORMALLY OPEN (N.O.)
FEEDER 1
FEEDER 2
OPEN
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Primary Loop System (simplified to show operation)
Siemens Industry Inc., Siemens Power Technologies International 3-17
• FAULT ON FEEDER 1 BETWEEN SWITCH 1 & CIRCUIT RECLOSER1.
Feeder breaker at substation 1 goes to lockout
2. All customers on distribution transformers on feeder 1 experience outage
3. All customers on feeder 2 receive normal power (possible voltage
sag if both feeders
from same substation)
DISTRIBUTION SUBSTATION 2
FEEDERBREAKER
DIST.TRANSF.
CIRCUITRECLOSER
LINEFUSES
MANUALSWITCH 1
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
MANUALSWITCH 2
CLOSED CLOSED
D#3, 2012, Loop Syst Simplified Faults-1.FCW
138 KV 13 KV
FEEDERBREAKER
DIST.TRANS 1
CIRCUITRECLOSER
LINEFUSES
MANUALSWITCH 1
DIST.TRANS 2
DIST.TRANS 3
DIST.TRANS 4
DIST.TRANS 5
DIST.TRANS 6
DIST.TRANS 7
DIST.TRANS 8
MANUALSWITCH 2
OPEN CLOSED
DISTRIBUTION SUBSTATION 1
TIE SWITCH (TS)NORMALLY OPEN (N.O.)
FEEDER 1
FEEDER 2
OPEN
FAULT
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Primary Loop System (simplified to show operation)
Siemens Industry Inc., Siemens Power Technologies International 3-18
• SERVICE RESTORATION FOR FAULT ON FEEDER 1 1.
Opening of manual switch 1 on feeder 1 and circuit recloser on feeder 1 to isolate fault
2. Closing of feeder 1 circuit breaker at substation 1 and N.O. tie
switch between feeders 1 & 2
3. Service restored without repair of fault, except for customers served from DT 3 and DT 4
DISTRIBUTION SUBSTATION 2
FEEDERBREAKER
DIST.TRANSF.
CIRCUITRECLOSER
LINEFUSES
MANUALSWITCH 1
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
DIST.TRANSF.
MANUALSWITCH 2
CLOSED CLOSED
D#3, 2012, Loop Syst Simplified Faults-2.FCW
138 KV 13 KV
FEEDERBREAKER
DIST.TRANS 1
CIRCUITRECLOSER
LINEFUSES
MANUALSWITCH 1
(OPEN)
DIST.TRANS 2
DIST.TRANS 3
DIST.TRANS 4
DIST.TRANS 5
DIST.TRANS 6
DIST.TRANS 7
DIST.TRANS 8
MANUALSWITCH 2
CLOSED OPEN
DISTRIBUTION SUBSTATION 1
TIE SWITCH (TS)NORMALLY OPEN (N.O.)
FEEDER 1
FEEDER 2
CLOSED
FAULT
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Siemens Industry Inc., Siemens Power Technologies International 3-19
Two HV feeds to each customer with primary selective service
Applications
Overhead or underground
Manual or automated
Mainline or lateral
Used for important loads that can tolerate a momentary interruption during transfer, but not a longer duration outage
Alternate feeder must have capacity to pickup additional load
Radial Distribution System (Primary Selective –Automatic Transfer)
N.O.
DISTRIBUTIONSUBSTATION
CE 2008,D#1,PRIMARY ATO, RADIAL CIRCUITS.FCW-2012 MOD
RADIALCIRCUITMAIN LINEREAL POWER FLOW
SUB
TRAN
SMIS
SIO
N SU
PPLY
LIN
ES
N.0. = NORMALLY OPENN.C. = NORMALLY CLOSED
N.C.
N.O.
N.O.
N.C.N.C.
N.O.
FEEDER 1
FEEDER 2
FEEDER 3
LOAD BREAKSWITCHES OR
CIRCUITBREAKERS
T1
T2
T3
RADIALFED
CUSTOMER
RADIALFED
CUSTOMER
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Siemens Industry Inc., Siemens Power Technologies International 3-20
Primary Selective System -
Load Break Switches or Breakers, Open or Closed Transition
Normal configuration of the system
Configuration after an operation due to permanent fault on primary circuit B
DISTRIBUTIONSUBSTATION
CIRCUIT A
CIRCUIT B
CIRCUIT A
CIRCUIT B
N.C. N.0.
XFR. 1
N.O. N.C.
XFR. 2
MOMENTARY INTERRUPTIONTO LOAD SUPPLIED FROMXFR. 2
VOLTAGE SAG FOR LOADSUPPLIED FROM XFR. 1 IF SUBSTATION BUS-TIE BREAKER IS NORMALLY CLOSED
XFR. 1 NORMAL SUPPLY = CIRCUIT A
XFR. 2 NORMAL SUPPLY = CIRCUIT B
DISTRIBUTIONSUBSTATION
CIRCUIT A
CIRCUIT B
CIRCUIT A
CIRCUIT BPERMANENT
FAULTN.C. N.0.
XFR. 1
CLOSED OPENED
XFR. 2
OPENED
D#1 2006 PRIMARY ATO FEEDER FAULT FCW-2012 MOD
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Siemens Industry Inc., Siemens Power Technologies International 3-21
Secondary Selective System Two HV Feeders and Distribution Transformers
Normal configuration of the system
Configuration after an operation due to a permanent fault
on Circuit B
DISTRIBUTIONSUBSTATION
CIRCUIT A
CIRCUIT B
CIRCUIT A
CIRCUIT B
N.O.
N.C.N.C.
N.O.
N.C.N.C.LV AIRCIRCUIT
BREAKERS
Momentary interruptionto half of load suppliedfrom each secondaryselective system.
Other half experiencesa voltage sag until faulted feeder breakeropens if substation bustie breaker is closed.
Half of load at each secondaryselective system connected to each bus section
Secondary tie breaker N.O.
DISTRIBUTIONSUBSTATION
CIRCUIT A
CIRCUIT B
CIRCUIT A
CIRCUIT B
N.C. N.C.LV AIRCIRCUIT
BREAKERS
PERMANENTFAULT
OPENEDOPENED
CLOSEDCLOSED
OPENED
D#1, 2006, Secondary Selective Feeder Fault.FCW, 2012 MOD
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Low-Voltage Spot Network System Unfaulted Conditions
Siemens Industry Inc., Siemens Power Technologies International 3-22
NETWORK (AREA)SUBSTATION
HV FEEDER 2
HV FEEDER 3
HV FEEDER 1
NETWORK TRANSFORMER
NETWORK PROTECTOR
SPOTNETWORK.
BUS
SPOTNETWORK
LOAD(480Y/277
OR208Y/120VOLTS)
CLOSEDN.C.
N.C.
N.C.
3-UNITSPOT NETWORK
2-UNITSPOT NETWORK
SPOT NETWORKLOAD
TO OTHERNETWORK
UNITS
CLOSED
CE DEC 2006 #1, SPOT NWK NORMAL-REV 2012.FCW
CLOSED
CLOSED
CLOSED
P P
P
P
P
P DIRECTION OF REALPOWER FLOW
• ALL HIGH VOLTAGE FEEDERS IN SERVICE
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Low-Voltage Spot Network System Faulted Condition
Siemens Industry Inc., Siemens Power Technologies International 3-23
NETWORK (AREA)SUBSTATION
HV FEEDER 2
HV FEEDER 3
HV FEEDER 1
NETWORK TRANSFORMER
NETWORK PROTECTOR
SPOTNETWORK.
BUS
SPOTNETWORK
LOAD(480Y/277
OR208Y/120VOLTS)
CLOSEDN.C.
OPEN
N.C.
3-UNITSPOT NETWORK
2-UNITSPOT NETWORK
SPOT NETWORKLOAD
TO OTHERNETWORK
UNITS
CLOSED
CE DEC 2006 #1, SPOT NWK FAULT,FDR OPEN, NWP CLOSED.FCW
CLOSED
CLOSED
CLOSED
P P
P
P
P
P DIRECTION OF REALPOWER FLOW
PERMANENTFAULT
• FAULT
ON HV FEEDER 2, FEEDER 2 BKR OPEN, ALL NWK PROTECTORS CLOSED
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Low-Voltage Spot Network System Fault Isolated From Spot Networks
Siemens Industry Inc., Siemens Power Technologies International 3-24
NETWORK (AREA)SUBSTATION
HV FEEDER 2
HV FEEDER 3
HV FEEDER 1
NETWORK TRANSFORMER
NETWORK PROTECTOR
SPOTNETWORK.
BUS
SPOTNETWORK
LOAD(480Y/277
OR208Y/120VOLTS)
CLOSED
OPEN
CLOSED
N.C.
OPEN
N.C.
PERMANENTFAULT
3-UNITSPOT NETWORK
2-UNITSPOT NETWORK
SPOT NETWORKLOAD
TO OTHER NETWORKUNITS, NETWORK PROTECTORS ON HV FDR. 2 OPEN
OPEN
CE DEC 2006 #1, SPOT NWK-FAULT ON FDR-REV 2012.FCW
CLOSEDP DIRECTION OF REAL
POWER FLOW
P
P
P
• FAULT
ON HV FEEDER 2, FEEDER 2 BKR OPEN, FDR 2 NWK PROTECTORS OPEN
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Siemens Industry Inc., Siemens Power Technologies International 3-25
Low-Voltage Spot Network System (continued)
THREE-UNIT 480-VOLT SPOT NETWORK SYSTEM
SPOT NETWORK(PARALLELING)BUS FROM WHICHLOAD IS SUPPLIED
NETWORKPROTECTOR
NETWORKTRANSFORMER
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Siemens Industry Inc., Siemens Power Technologies International 3-26
PARALLELING BUS FOR THREE NETWORK TRANSFORMERS / PROTECTORS
CABLES TO NETWORK PROTECTORS
SILVER-SANDCABLE LIMITERS
NWK XFR. &NWP.
NEUTRAL BUSINSULATED PHASE BUSES
CABLES TOCUSTOMERSERVICEEQUIPMENT
Low-Voltage Spot Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-27
Low-Voltage Spot Network System Con Edison 480-Volt Design
• EACH NETWORK TRANSFORMER AND PROTECTOR IN SEPARATE VAULT / COMPARTMENT • PARALLELING BUS FROM INSULATED INTEGRAL WEB ALUMINUM BUS
- CABLES FROM TRANSFORMERS TO NWP’S HAVE LIMITERS AT BOTH ENDS
NETWORK XFR. 1
X0HV FDR. 1
GRD. SW.NETWORK XFR. 3
X0HV FDR. 3
GRD. SW.NETWORK XFR. 2
X0HV FDR. 2
GRD. SW.
NWP.1
NWP.2
NWP.3
LIMITERED CABLESPHASE ISOLATED IF LT 50 FT
NETWORK PROTECTORCOMPARTMENTS ON
CUSTOMER PROPERTYWITH FRAME MOUNTED NETWORK PROTECTOR
INTEGRAL WEB ALUMINUMPARALLELING BUS
CLF CLF CLF
SERVICE TAKE OFFS TO CUSTOMER SWITCHGEARSQUARE/RECTANGULAR HOLLOW COPPER BUS
CLF CLF
TRANSFORMER VAULT 1 TRANSFORMER VAULT 2 TRANSFORMER VAULT 3
DISK #18, SPOT LAYOUT-5.FCW
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Siemens Industry Inc., Siemens Power Technologies International 3-28
Low-Voltage Spot Network System Con Edison 480-Volt Design
SINGLE-CONDUCTORPRIMARY CABLESAND SPLICES
GROUNDING SWITCHOPERATING HANDLE
NETWORK TRANSFORMER IN SIDEWALK VAULT
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Siemens Industry Inc., Siemens Power Technologies International 3-29
Low-Voltage Spot Network System Con Edison 480-Volt Design
• PHASE ISOLATED CABLES IN “GAP”
BETWEEN NETWORK TRANSFORMERAND NETWORK PROTECTOR IN “PROTECTOR COMPARTMENT”
CABLES TO NETWORK PROTECTOR COMPARTMENT
CABLES TO NETWORK TRANSFORMER LOW-VOLTAGE TERMINALS
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Siemens Industry Inc., Siemens Power Technologies International 3-30
Low-Voltage 480-Volt Spot Network, Con Ed Separately Mounted Network Protector
PARALLELING BUS
NETWORK PROTECTORFUSES –
SILVER-SAND
TYPE
SERVICE TAKE OFF TO CUSTOMER SWITCHGEAR
MICRO PROCESSORNETWORK PROTECTORRELAY, TYPE MNPR
CABLE CONNECTIONSFROM NETWORK TRANSFORMER TERMINATE AT BOTTOMOF NETWORK PROTECTOR
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Siemens Industry Inc., Siemens Power Technologies International 3-31
Low-Voltage 480-Volt Spot Network, Con Edison Paralleling Bus & Service Takeoff
INSULATED PARALLELING BUSPHASES 4, 5, 6 PHASE 6 OF PARALLELING BUS
SERVICE TAKEOFF
SERVICE TAKEOFF CURRENT-LIMITING FUSE
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Siemens Industry Inc., Siemens Power Technologies International 3-32
Low-Voltage 480-Volt Spot Network, Cut Away of “Blown”
Silver-Sand Fuse
TYPE OF FUSE USED IN CON EDISON 480-VOLT SPOT NETWORKS FOR:• NETWORK PROTECTOR FUSE• SERVICE TAKE OFF FUSE
MULTIPLE SILVERELEMENTS
Note:
Sand has been removed from the fuse body. This fuse blew under a high fault current condition.
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Siemens Industry Inc., Siemens Power Technologies International 3-33
• MICRO PROCESSOR NETWORK PROTECTOR RELAYControls automatic operation of network protector (tripping and closing)
LED STATUSINDICATORS
TERMINALS FOR CONNECTIONS TONETWORK PROTECTORCONTROL WIRING
Low-Voltage Spot Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-34
EXAMPLES OF HIGH-RISE BUILDINGSSUPPLIED BY 480-VOLT SPOT NETWORK SYSTEMS.
SPOT NETWORKS TYPICALLY LOCATEDAT EITHER GRADE LEVEL, OR IN THEUPPER FLOORS OF THE BUILDING.
LARGE BUILDINGS ARE SERVED FROM MULTIPLE SPOT NETWORKS, LOCATED ON VARIOUS FLOORS.
Low-Voltage Spot Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-35
Many parallel paths from the distribution (area) substation to each load supplied from the low-voltage network (208Y/120 Volts)
Fault on high-voltage (HV) primary feeder or in network transformer does not cause an outage to load supplied from the low-voltage network
Fault in LV network causes outages to no or only a small number of customers
Primary feeders and network transformers can be removed from service for work or repair without causing an outage to customers
System designed for single or double contingency
Used in many major cities in the USA and abroad (Con Edison is largest user of secondary networks)
Provides highest reliability and service continuity possible with conventional types of power distribution systems
Low-Voltage Grid (Street) Network System
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Low-Voltage Grid (Street) Network System Normal Conditions, No Fault
Siemens Industry Inc., Siemens Power Technologies International 3-36
3
NETWORKSUBSTATION
FEEDER BREAKERS
CABLELIMITER
NETWORK UNIT
LV CABLES
PRIMARY
P + jQ3-P 4-W LOAD
SWITCHTRANSFORMERPROTECTORPROTECTOR FUSE
FEEDERS
3-1
3-2
3-3
2-1
2-2
2-3
1-1
1-2
1-3
2
1
FEEDER 2
FEEDER 1
FEEDER 3
2 POSITIONGRD. SWITCH
3 POSITIONGRD. SWITCH
N.C.BUSTIE
N.C.BUSTIE
SECONDARY MAINS208Y/120 VOLTS
3-4
P + jQ
P + jQ
BUS HOLE/CRAB VAULT/RING BUS
LVNET105-A-H.FCW, 0.165X
FUSIBLE CRABMOLECABLE RING BUSRIGID BUSFUSE BOX
ISOLATED SPOTNETWORK
480Y/277 VOLTS
P + jQ
3-5 2-4
P
P
P
P
PINDICATES DIRECTIONOF POWER FLOW IN CLOSED PROTECTORSON FEEDER 2
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LV Grid (Street) Network, Fault on Feeder 2 Feeder Bkr Open, All Network Protectors Closed
Siemens Industry Inc., Siemens Power Technologies International 3-37
3
NETWORKSUBSTATION
FEEDER BREAKERS
CABLELIMITER
NETWORK UNIT
LV CABLES
PRIMARY
P + jQ3-P 4-W LOAD
SWITCHTRANSFORMERPROTECTORPROTECTOR FUSE
FEEDERS
3-1
3-2
3-3
2-1
2-2
2-3
1-1
1-2
1-3
2
1
FEEDER 2
FEEDER 1
FEEDER 3
2 POSITIONGRD. SWITCH
3 POSITIONGRD. SWITCH
N.C.BUSTIE
N.C.BUSTIE
SECONDARY MAINS208Y/120 VOLTS
3-4
P + jQ
P + jQ
BUS HOLE/CRAB VAULT/RING BUS
LVNET105-A-H-FLT.FCW, 0.165X
FUSIBLE CRABMOLECABLE RING BUSRIGID BUSFUSE BOX
ISOLATED SPOTNETWORK
480Y/277 VOLTS
P + jQ
3-5 2-4
P
P
P
P
PINDICATES DIRECTIONOF POWER FLOW IN CLOSED PROTECTORSON FEEDER 2
OPEN
FAULT
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Low-Voltage Grid (Street) Network System Fault on Feeder 2 Isolated, No Outages to NWK
Siemens Industry Inc., Siemens Power Technologies International 3-38
3
NETWORKSUBSTATION
FEEDER BREAKERS
CABLELIMITER
NETWORK UNIT
LV CABLES
PRIMARY
P + jQ3-P 4-W LOAD
SWITCHTRANSFORMERPROTECTORPROTECTOR FUSE
FEEDERS
3-1
3-2
3-3
2-1
2-2
2-3
1-1
1-2
1-3
1
FEEDER 2
FEEDER 1
FEEDER 3
2 POSITIONGRD. SWITCH
3 POSITIONGRD. SWITCH
N.C.BUSTIE
N.C.BUSTIE
SECONDARY MAINS208Y/120 VOLTS
3-4
P + jQ
P + jQ
BUS HOLE/CRAB VAULT/RING BUS
LVNET105-C-H.FCW, 0.165X
FUSIBLE CRABMOLECABLE RING BUSRIGID BUSFUSE BOX
ISOLATED SPOTNETWORK
480Y/277 VOLTS
P + jQ
3-5 2-4
OPENOPEN
OPEN
OPEN
OPEN
ALL NWP’S ON FEEDER 2 OPEN
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Low-Voltage Grid (Street) Network System Fault Repaired, Feeder 2 Re-energized at Station
Siemens Industry Inc., Siemens Power Technologies International 3-39
3
NETWORKSUBSTATION
FEEDER BREAKERS
CABLELIMITER
NETWORK UNIT
LV CABLES
PRIMARY
P + jQ3-P 4-W LOAD
SWITCHTRANSFORMERPROTECTORPROTECTOR FUSE
FEEDERS
3-1
3-2
3-3
2-1
2-2
2-3
1-1
1-2
1-3
2
1
FEEDER 2
FEEDER 1
FEEDER 3
2 POSITIONGRD. SWITCH
3 POSITIONGRD. SWITCH
N.C.BUSTIE
N.C.BUSTIE
SECONDARY MAINS208Y/120 VOLTS
3-4
P + jQ
P + jQ
BUS HOLE/CRAB VAULT/RING BUS
LVNET105-D-H.FCW, 0.165X
FUSIBLE CRABMOLECABLE RING BUSRIGID BUSFUSE BOX
ISOLATED SPOTNETWORK
480Y/277 VOLTS
P + jQ
3-5 2-4
CLOSED
OPEN
OPEN
OPEN
OPEN
Note:All NWP’s on Feeder 2 open when breaker reclosed.
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Siemens Industry Inc., Siemens Power Technologies International 3-40
Low-Voltage Grid (Street) Network System Primary Cable Types (3 & Single Conductor)
PAPER INSULATED LEAD COVERED
(PILC)
SOLID DIELECTRIC INSULATIONETHYLENE PROPYLENE RUBBER (EPR)
CROSS LINKED POLYETHYLENE
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Siemens Industry Inc., Siemens Power Technologies International 3-41
• NETWORK PRIMARY FEEDER CABLE SPLICES (STOP JOINTS)
THREE-CONDUCTOR PAPER INSULATED LEAD COVERED (PILC) CABLE TO SINGLE CONDUCTOR SOLID DIELECTRIC CABLE
Low-Voltage Grid Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-42
• NETWORK UNIT (TRANSFORMER & PROTECTOR) IN VAULT
NETWORKTRANSFORMER NETWORK
PROTECTOR
DISCONNECTAND
GROUNDINGSWITCH
600 AMPERESEPARABLE
CONNECTORS
CABLELIMITERS
LV C
ABLE
S TO
ADJ
ACEN
T BU
SHO
LE /
MAN
HOLE
HIG
H VO
LTAG
EFE
EDER
CAB
LE T
OST
ATIO
N BR
EAKE
R
32
CE 2005, #1, Network Unit.FCW
Low-Voltage Grid Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-43
• MANHOLE ADJACENT TO NETWORK TRANSFORMER VAULT•
SOME CABLES GO TO NETWORK PROTECTOR
•
SOME CABLES GO TO LOAD AND OTHER CABLES GO TO STREET NETWORK
MAIN BUS FOR LV CABLE CONNECTIONS
CABLE LIMITERS
Low-Voltage Grid Network System (continued)
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Low-Voltage Grid Network System (continued)
Siemens Industry Inc., Siemens Power Technologies International 3-44
TRANSFORMER SUSPENDED TO RAISE ABOVE VAULT FLOOR
SUBMERSIBLENETWORKPROTECTOR
FOUR 500 KCMIL CABLES PER PHASE
HV TERMINALS & GROUND SWITCH HANDLE ON TOP OF TRANSFORMER TANK AT OPPOSITE END• CON EDISON SUBMESIBLE NETWORK TRANSFORMER & PROTECTOR
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Siemens Industry Inc., Siemens Power Technologies International 3-45
• SILVER-SAND CABLE LIMITER FOR 500 KCMIL SECONDARY CABLES
SPADETERMINALFOR BOLTINGTO BUS
COMPRESSIONTERMINAL FORCABLE CONDUCTOR
SILVER FUSIBLEELEMENT
M-SPOT TO AIDLOW-CURRENT CLEARING
Low-Voltage Grid Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-46
• FUSIBLE CRABS IN MANHOLE FOR CONNECTING & FUSING LV CABLES FIVE-WAY BY FIVE-WAY CRABS
NEUTRALS
Low-Voltage Grid Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-47
Low-Voltage Grid Network System Fusible Crabs For Protection of LV Cables
SERVICE BOX WITH THREE THREE-WAY BY THREE-WAY FUSIBLE CRABS (ONE PER PHASE)
CUTAWAY OF FUSIBLE CRABSHOWING FUSE LINKS (CABLELIMITERS) THAT MELT ANDINTERRUPT SHORT CIRCUITCURRENTS
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Siemens Industry Inc., Siemens Power Technologies International 3-48
• CONVENTIONAL 216 VOLT CABLE LIMITER (LUG LIMITER)
RUBBER BOOTSPADETERMINAL FORBOLTING TOBUS BAR
CABLE RECEPTACLE FUSIBLE SECTION
ENCLOSURE TO ABSORBE HEAT ANDPREVENT CABLE MOVEMENT FOLLOWINGMELTING
Low-Voltage Grid Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-49
TRANSFORMERVAULT500/560 KVA
BUS HOLE / MANHOLE/CRAB VAULT
500 KCMILLIMITER
NWP FUSE
DISK CE TOPIC 1 2006 FILE: NWPFUSELIMITER1 FCW
FAULT OR 3-PHASEGROUND APPLIEDAT STATION
PRIMARY SIDE
208-VOLT SIDE
DESIRED COORDINATION FOR HUNG NWP
NWP FUSE BLOWS BEFORE CABLE LIMITERSCAN BLOW
Low-Voltage Grid Network, Coordination of NWP Fuse and Cable Limiters Under Backfeed
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Siemens Industry Inc., Siemens Power Technologies International 3-50
MEASUREMENT OF CURRENT SPLIT BETWEEN PARALLEL LOW -VOLTAGE CABLES TO PRODUCE DATA FOR COORDINATION OF LIMITERS AND NWP FUSES
SPLIT-
CORE CT’S AND AUXILIARY CT’S TO SUPPLY
OSCILLOSCOPES FOR WAVEFORM RECORDS
TECHNICIANS INSTALLING SPLIT CORE CT’S ON 500 KCMIL LV CABLES
Low-Voltage Grid Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-51
• MEASUREMENT OF CURRENT SPLIT BETWEEN PARALLEL LV CABLES
NICOLET 4-
CHANNEL DIGITAL SCOPES IN VAN FOR RECORDING CURRENT WAVEFORMS IN LV CABLES
5 &1/4 INCH FLOPPY DISK DRIVES FOR STORING CURRENT WAVES
Low-Voltage Grid Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-52
VAN WITH INSTRUMENTATION FOR MEASURING CURRENT SPLIT IN LOW-VOLTAGE CABLES
Low-Voltage Grid Network System (continued)
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Siemens Industry Inc., Siemens Power Technologies International 3-53
Low-Voltage Grid Network System (continued)
• COVERS FOR MANHOLES WITH PRIMARY AND SECONDARY CABLES
SLOTTED COVER SOLID COVER
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Siemens Industry Inc., Siemens Power Technologies International 3-54
Low-Voltage Grid Network System (continued)
TRANSFORMER SIDEWALK VAULTGRATING FOR VENTILATIONTRANSFORMER MANHOLE (TM) IN STREET
WITH GRATINGS FOR VENTILATION(TYPICALLY 500 KVA XFR AND NETWORK
PROTECTOR IN SUBMERSIBLE ENCLOSURE)
• WHAT IS SEEN BY THE AVERAGE PEDESTRIAN
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Siemens Industry Inc., Siemens Power Technologies International 3-55
Primary Network -
4.16 KV FEEDERS Simplified Diagram
SUB-TRANSMISSION CIRCUITS:13.2 KV, 27 KV, OR 33 KV
NETWORKED PRIMARYCIRCUIT VOLTAGE
4.16 KV
SERVICE VOLTAGESFROM DIST. TRANSFORMERS:
120/240 V 1-PHASE208Y/120 V 3-PHASE480Y/277 V 3-PHASE
PRIMARY NWK UNITTRANSFORMER TYPICAL SIZES:
6250 KVA7000 KVA10000 KVA
SUB TRANSMISSIONCIRCUITS
PRIMARY NETWORK UNIT
RADIALPRIMARYFEEDER
DISTRIBUTION TRANSFORMER
SERV
ICES
SECONDARYMAINS
PRIMARYTIEFEEDERS
PRIMARYSUB-FEEDERS
SERV
ICES
g
SERV
ICES
SERV
ICES
d c e f
C
E
A
Bk a
h
b
SERV
ICES
D 2006 #2 TWO BKR PER FDR PRI NWK FCW
ESCO
ESCO
ESCO
ESCO
ESCOESCO
SUB. 1
SUB. 2
SUB. 3
SUB. 4
ST 1ST 2
ST 3ST 4
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Siemens Industry Inc., Siemens Power Technologies International 3-56
Primary Network Unit - 4 kV Unit Substation
TRANSFORMER WITH LOAD TAP CHANGER13.2 KV, 27 KV, OR 33 KV TO 4.16 KV
4 KV METAL-CLADSWITCHGEAR WITHMAIN AND FEEDERBREAKERS, ANDPROTECTIVE RELAYS
HV DISCONNECT AND GROUNDING SWITCH
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Siemens Industry Inc., Siemens Power Technologies International 3-57
Radial Systems:
Rural and suburban areas
Small towns and boroughs
Looped Systems:
Small cities, suburban and rural areas
Primary Selective & Secondary Selective:
More critical loads and service areas (hospitals, manufacturing plants, radio/TV stations, large buildings) which can tolerate momentary outages –
Critical loads fed from UPS systems
Secondary (Low-Voltage) Networks
Large city downtown areas
Special loads in suburban areas
Provide highest reliability possible with conventional types of power distribution systems
Where are the Different Systems Used?
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Siemens Industry Inc., Siemens Power Technologies International 3-58
Overhead and underground systems may be any of the five basic configurations discussed
Radial
Looped
Primary selective or secondary selective
Primary network (4.16 kV at Con Edison)
Low-voltage network
Underground distribution is often used in urban environments, and is the system of choice for most new residential construction. In rural areas overhead is still preferred.
Underground systems benefit from reduced exposure to lightning, wind, trees, etc., but can be higher in cost for initial installation, repairs and replacement.
Overhead or Underground?
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Siemens Industry Inc., Siemens Power Technologies International 3-59
Example of a Looped Underground System
THREE-PHASE OVERHEAD PRIMARY CIRCUIT
FUSED CUTOUT
CABLE TERMINATOR
SURGE ARRESTER
RISER POLEGROUND
SEPARABLECONNECTOR N.C. SWITCH
N.O. SWITCH
DISTRIBUTION TRANSFORMERHV WINDINGS FROM PHASE
TO NEUTRAL TRANSFORMER FUSECURRENT LIMITING
TRANSFORMER FUSEEXPULSION
RISER POLE
UNDERGROUND LOOP, EITHER THREE-PHASE OR SINGLE PHASE
Note: Surge arresters at N.O. point in loopin some 25 and all 35 kV class systems
GROUND RODAT EACH XFR.
NOTE: Normal open point may be at one of the riser poles
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Siemens Industry Inc., Siemens Power Technologies International 3-60
Type of System Outages/yr Average outage duration/ min
Momentary interruptions/yr
Radial 0.3 - 1.3 90 5-10
Primary Auto-Loop 0.4 -0.7 65 10 - 15
URD (3ph overhead serving looped lateral)
0.4 - 0.7 60 4 - 8
Primary Selective 0.1 - 0.5 180 4 - 8
Secondary Selective 0.1 - 0.5 180 2 - 4
Grid Network 0.005 - 0.020 135 0
Spot Network 0.02 - 0.10 180 0 - 1
From Electrical World magazine article by Settembrini, Fisher & Hudak, May 1992
Measured Reliability of System Configurations
© 2012, Siemens Industry Inc., all rights reserved
Distribution Feeders
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Siemens Industry Inc., Siemens Power Technologies International 3-62
• Typical Feeder Layout (Radial)
• Voltage levels
• Loading
• Equipment
• Conductor Arrangements/Grounding
Overview
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Siemens Industry Inc., Siemens Power Technologies International 3-63
12.5
KV
SUBS
TATI
ON
BUS
B
SMAIN 3-P FEEDER
EXPRESS PORTION
3-PHASEOHLATERAL
3-PHASEDIST.XFR
3-PHASEDIST. XFR
BANK
208Y/120
480Y/277
FIXEDCAPACITOR
BANK
R
RATIOBANK
12.5 KVTO
4.16 KV
N.O.
TIE TO ADJACENT
FEEDER
SWITCHEDCAP. BANK
VOLTAGEREGULATORS
1-PHASEDT 2.4 KV
TO 120/240 V
1-PHASELATERAL URBAN AREA
SECONDARY4-20 HOMES
3-PHASERECLOSER
1-PHASE UGLATERAL
PAD-MOUNTEDTRANSFORMER
TIE TOADJACENT
FEEDERN.O.
N.C.
N.C.
3-PHASESECTIONALIZER
FUSEDCUTOUT
1-P LATERAL
RURAL AREA1 CUSTOMER
PER DIST. XFR.
CL FUSE
120/240 VSINGLEPHASE
3-PHASESWITCH
N.C.
FEEDERBREAKER(RECLOSING)
UGSERVICES
4.16KV
R1-P
RECS.
12.5 KV
CABLE TERMINATOR
Example of a Distribution Feeder One Line (To illustrate equipments applied)
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Siemens Industry Inc., Siemens Power Technologies International 3-64
Common US Percent ofkV Class Voltages Distribution
(line to line kV) Systems in use4.16
5 4.8 5 - 10%
12.4715 13.2 60 - 70%
13.820.78
25 22.86 15 - 20%24.94
35 34.5 5 - 10%
Primary Feeder Voltage Classes
OTHER DISTRIBUTION NOMINAL PRIMARY VOLTAGES AT CON EDISON• 27 KV (BROOKLYN, QUEENS)• 33 KV (STATEN ISLAND)
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Siemens Industry Inc., Siemens Power Technologies International 3-65
Primary Feeder Loading Levels
The amount of load supplied by the circuit depends upon several factors. These include:
The kVA capacity of the sub-station equipment & number of primary feeders
The ampere capacity of the primary feeder conductors and roadside construction limitations
Requirements to backup another primary feeder
The voltage rating of the primary feeder
The length of the primary feeder, and voltage drop along the feeder for the given load distribution
For 5kV -
up to about 3 MVA per circuit
For 15kV -
up to about10 MVA per circuit
For 25kV -
up to about 15 MVA per circuit
For 35kV -
up to about 25 MVA per circuit
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Siemens Industry Inc., Siemens Power Technologies International 3-66
Four-wire multigrounded neutral (grounded system)
Four-wire unigrounded neutral (grounded system)
Three-wire unigrounded (grounded system)
Three-wire ungrounded (delta)
Four-wire multigrounded neutral systemsare the predominant type in the USA.
Note:
For three-wire uni-grounded systems and three-wire ungrounded (delta) systems, the primary windings of all distribution transformers are connected between phases.
Distribution Primary Feeder Conductor / Grounding Arrangements
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Primary Feeder Conductor / System Grounding Arrangements
4-WIRE MULTI-GROUNDED NEUTRAL
4-WIRE UNI-GROUNDED NEUTRAL
A
B
C
MULTI- GROUNDED NEUTRAL
A
B
C
UNI-GRD. NEUTRAL
3-WIRE UNI-GROUNDED
A
B
C
3-WIRE UNGROUNDED
A
B
C
SOURCESUBSTATION
TRANSFORMERCONNECTIONS
SOURCESUBSTATION
TRANSFORMERCONNECTIONS
SOURCESUBSTATION
TRANSFORMERCONNECTIONS
SOURCESUBSTATION
TRANSFORMERCONNECTIONS
Dist Sys Grd, D#1-2010, Primary Conductor Arrangements.FCW
L or 0 R,L or 0
R,L or 0
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System Type Advantages
3-wire Ungrounded(Delta)
Not used above 4800 volts by utilities
Better Phase Balancing as no line-to-neutral loads
Low energy to ground faults –
Can remain energized for SLG Fault when cable capacitance does not allow more than 5 to 10 amperes
of ground fault current(Concern for Arcing Ground Faults & High Transient Overvoltages)
Lower EMF and Stray Voltage
4-wire multi-grounded neutral
Lower cost for single-phase laterals (Transformer cost, Fusing Cost, Surge arrester cost)
Phase to neutral faults easily detected and isolated (relays or fuses) to minimize number of customer outages
Lower voltage rated surge arrestors and equipment (graded insulation) may be used resulting in lower cost for components
Comparison of 3-Wire Ungrounded (Delta) vs. 4-Wire Multi-Grounded Neutral System
CON EDISON NON-NETWORK PRIMARY DISTRIBUTION SYSTEMS, AND 4 KV PRIMARY NETWORK SYSTEMSARE 4-WIRE MULTI-GROUNDED NEUTRAL SYSTEMS.
© 2012, Siemens Industry Inc., all rights reserved
Examples of Distribution Primary Conductor Arrangements
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Siemens Industry Inc., Siemens Power Technologies International 3-70
Crossarm
Insulator Phase
Conductor
Neutral
Conductor
Distribution Pole-Top , Typical Configuration 3 Phase 4-Wire Multi-Grounded Neutral
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3-PHASE 4-WIRE
TOP PHASE ON RIDGE PIN
OUTER PHASES ON FIBERGLASS RODS & PORCELEAN INSULATORS
Four Wire Multi-Grounded Neutral System Armless Construction
MULTI-GROUNDEDNEUTRAL CONDUCTOR
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Siemens Industry Inc., Siemens Power Technologies International 3-72
Four Wire Multi-Grounded Neutral System Armless Construction (continued)
34" 34"
48"
72.5" 68.4"
Oa Oc
Ob
n
dbn = 90.0"
13 KV ARMLESS CONSTRUCTIONAPPROXIMATE PHASE-TO-PHASE ANDPHASE-TO-NEUTRAL SPACINGS
PHASE WIRE = 477 MCM ALRϕ = 0.198 Ohms / mileGMRϕ = 0.02501 Feet
NEUTRAL WIRE = 4/0 COPPERRn = 0.278 Ohms / mile
GMRn = 0.01668 Feet
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Siemens Industry Inc., Siemens Power Technologies International 3-73
Four Wire Multi-Grounded Neutral Systems Spacer Cable
12.47 KV SYSTEM, WOODED AREA 13.2 KV SYSTEM, SUBSTATION EXIT CIRCUITS
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Four-Wire Multi-Grounded Neutral System Crossarm Construction
Three single phase reclosers, installed in a line with crossarm construction
Note:Fuse cutout mountings on crossarm to allow bypassing reclosersfor maintenance.
Fuse tubes stored in metal box attached to pole
MULTI-GROUNDEDNEUTRAL CONDUCTOR
PHASE CONDUCTORS
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Single-Phase Lateral Circuits (part of a multi-grounded neutral system)
PRIMARY PHASE WIRE
NEUTRALWIRE
Note: Cross arm not required on single-phase multi-grounded neutral lines.
NEUTRALWIRE
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Note:
LINE SHOWN IS FOR ASUB-TRANSMISSION CIRCUIT
Three-Wire Uni-Grounded System
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OTHER MATERIALS FOR OH LINE CONDUCTORS:• COPPER• ALUMINUM COVERED STEEL REINFORCED (ACSR)• ALUMINUM COVERED ALUMINUM REINFORCED (ACAR) • ALL ALUMINUM ALLOY CONDUCTORS (AAAC)• COPPERWELD • STEEL (DURING WW2)
Bare and Covered Conductors for OH Systems
TYPICAL STRANDING FOR BARE CONDUCTORS:
7 19 37 61
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Underground Distribution Cables
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USED MAINLY IN URBAN AREA SYSTEMS AND IN LV NETWORKS, INSTALLEDIN DUCTS.
ALSO USED FOR AERIAL CABLES. PILC CABLES IN CON ED 13 & 27 KV SYSTEMS.
• LEAD
SHEATH WITH JACKET
Single Conductor Cable Types (Distribution)
PHASE CONDUCTOR
INSULATION SHIELD
CONDUCTOR SHIELD
INSULATION
LEAD SHEATH
JACKET
CABL
E O
UTSI
DEDI
AMET
ER
INSIDE RADIUS OF LEAD SHEATHCE 2005, D#2, 1-0 19 STRAND 35 KV LEAD SHEATH 2 TIMES.FCW
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Siemens Industry Inc., Siemens Power Technologies International 3-80
• MULTI-WIRE
CONCENTRIC NEUTRAL
USED IN URD SYSTEMS, BOTH WITH AND WITHOUT JACKET.
NEUTRAL IS INTENDED TO CARRY LOAD CURRENT.
Single Conductor Cable Types (Distribution) (continued)
PHASE CONDUCTOR
CONDUCTOR SHIELD
INSULATION
INSULATION SHIELD
NEUTRAL WIRE
JACKET
CABL
E O
UTSI
DEDI
AMET
ER
RADIUS OF CIRCLE FORMEDBY NEUTRAL WIRE CENTERS
CE 2005, D#2, 1-0 19 STRAND 35 KV MWIRE-2 TIMES.FCW
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©20
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Siemens Industry Inc., Siemens Power Technologies International 3-81
• FLAT-STRAP CONCENTRIC NEUTRAL
USED TO REPLACE PILC LEAD SHEATH CABLES IN NETWORK SYSTEMS.
USED IN URD NON-NETWORK SYSTEMS –
NEUTRAL TO CARRY UNBALANCED LOAD CURRENTS.
Single Conductor Cable Types (Distribution) (continued)
PHASE CONDUCTOR
CONDUCTOR SHIELD
INSULATION
INSULATION SHIELD
FLAT STRAP NEUTRALJACKET
INSIDE RADIUS OFFLAT STRAP NEUTRAL
CABL
E O
UTSI
DEDI
AMET
ER
CE 2005, D#2, 1-0 19 STRAND 35 KV FLAT STRAP 2 TIMES.FCW
© 2012, Siemens Industry Inc., all rights reserved
Questions?
© 2012, Siemens Industry Inc., all rights reserved
Tab 4 Some Basic Relationships Distribution System Engineering -
Course 1
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Inc., Siemens Power Technologies International 4-2
VPN
= PHASE-TO NEUTRALVOLTAGE
VPP
= PHASE-TO-PHASEVOLTAGE
VPNVPN
VPP
ϕA ϕB
ϕC
NEUTRAL CONDUCTOR(common to both primary and secondary 1ϕ
3W systems)
VPN
VPP
VPPϕA
ϕB
ϕC
Voltage Relationships in Three-Phase Balanced Circuits
Note:
Primary winding of distribution transformer connected from phase
to neutral
• THREE-PHASE OVERHEAD LINE (4.16 KV) WITH UNDERBUILT 1ϕ
3 W 120/240 V SECONDARY
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Siemens Industry Inc., Siemens Power Technologies International 4-3
Voltage Relationships in Three-Phase Balanced Circuits (continued)
VoltsVV PPPN 7506
313000
33
PPPN
VV
VPP = PHASE-TO-PHASE VOLTAGE
VPN
= PHASE-TO-NEUTRAL VOLTAGE
EXAMPLE:
VPP
= 13000 VOLT
V
A
B
C
N
PP VPP
V
V
PN
PP
NEUTRAL CONDUCTOR
PHASE CONDUCTORS
VPN
VPN
D# 2005 BR, Line Voltage Relationships.FCW
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Siemens Industry Inc., Siemens Power Technologies International 4-4
AmperesKV
KVAKVMVAI
P
T
P
TP 33
*1000 Amperes
KVKVA
KVMVAI
S
T
S
TS 33
*1000
MVAT
= TRANSFORMER SELF COOLED (OA) RATING IN MVAKVAT
= TRANSFORMER SELF COOLED (OA) RATING IN KVA
KVP
= PRIMARY WINDING RATED PHASE-TO-PHASE VOLTAGE IN KV
KVS
= SECONDARY WINDING RATED PHASE-TO-PHASE VOLTAGE IN KV
• RATED OA CURRENT ON PRIMARY SIDE IN AMPERES
• RATED OA CURRENT ON SECONDARY SIDE IN AMPERES
EXAMPLE CALCULATION: 3-PHASE SUBSTATION TRANSFORMER
MVAT
= 58 KVP
= 138
KVS
= 13.0
AmperesIP 7.2420.13830.58*1000 AmperesIS 9.575,2
0.1330.58*1000
Rated Current of Three-Phase Transformer
MVAT
KVSKVPIP SI
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• PORTION OF NAMEPLATE OF 2000/2240 KVA NETWORK TRANSFORMER
• RATED LINE CURRENT ON HIGH VOLTAGE (PRIMARY) SIDEAT NOMINAL PHASE-TO-PHASE VOLTAGE OF 13.75 KV:
AmperesKV
KVAKVMVAI
P
T
P
TP 98.83
75.1332000
331000
THE RATED LINE
CURRENT ON THE HV SIDE WHEN SET ON TAP CHANGER POSITION 3 IS 84.0 AMPERES (See nameplate above)
Rated Current of Three-Phase Transformer (continued)
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AmperesKVMVAI P
P3
*1000 33
MVA3P
= Three-phase short circuit capacity in MVA
KVΦΦ
= Phase-to-phase voltage at location of MVA3P
in kV
I3P
= Current in fault path for three-phase short
EXAMPLE CALCULATION:
MVA3P
= 500.0 KVΦΦ
= 22.9
AmperesI P 606,129.223
0.500*10003
MVA3P
Conversion of Short Circuit (Fault) MVA to Three-Phase Fault Current in Amperes
THREE-PHASESHORT CIRCUIT
INCOMING LINE OUTGOING LINE
SWITCHES
MVA3P
KVO O
INCOMINGLINE (CABLE)
OUTGOINGLINE (OH)
XFR.FUSES
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Siemens Industry Inc., Siemens Power Technologies International 4-7
OhmsMVAKV
ZP
TH3
2
MVA3P = Three-phase short circuit capacity in MVA
KVΦΦ
= Phase-to-phase voltage at location of MVA3P in kV.
GIVEN:
EQUIVALENT IMPEDANCE AND VOLTAGE:
VoltsKV
ETH 3*1000
EXAMPLE:
MVA3P
= 500.0 KVΦΦ
= 22.9
OhmsZTH 04882.1500
9.22 2
VoltsETH 3.221,133
9.22*1000
AmperesZEI
TH
THCIRCUITSHORT 606,12
04882.13.221,13
Conversion of Three-Phase Short Circuit (Fault) MVA to Thevenin Equivalent Circuit
ZTHETH
THEVENIN EQUIVALENT
ISC
INCOMINGLINE (CABLE)
XFR.FUSES
OUTGOINGLINE (OH)
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Siemens Industry Inc., Siemens Power Technologies International 4-8
currentratedOArtransformeofmultiplesunitper
MVAMVAZ
I
P
TT
P )(100
100
3%
3
MVA3P = Available three-phase fault MVA at primary terminals of transformer in MVA.
MVAT = Transformer self cooled (OA) rating in MVA
ZT%
= Transformer impedance in % on transformerOA rating
KVS
= Transformer secondary rated phase-to-phase voltage in kV
MVA3P
LOCATION OF 3-PHASE FAULT
AmperesKVMVA
MVAMVAZ
IS
T
P
TT
P
3*1000
100
100
3%
3
CURRENT IN FAULT PATH AT SECONDARY TERMINALS (I3P
):
Current for a Three-Phase Fault at Secondary Terminals of a Three-Phase Transformer
RATED CURRENT OF TRANSFORMERSECONDARY WINDING
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Siemens Industry Inc., Siemens Power Technologies International 4-9
currentratedOArtransformeofunitper
MVAMVAZ
I
P
TT
P
3%
3
100
100
AmperesKVMVA
MVAMVAZ
IS
T
P
TT
P
3*1000
100
100
3%
3
currentratedOArtransformeofunitperI P 899.365.25
100
20005810075.22
1003
ASSUMPTIONS:1.Impedance angle of primary supply system and transformer are the
same.2.
Voltage at the secondary terminals of the xfr, prior to fault, is the transformer rated secondary volta
EXAMPLE CALCULATIONS:
MVA3P
= 2000.0 MVAT
= 58.0 ZT%
= 22.75 % KVS
= 13.0
AmperesI P 3.043,10)87.575,2(*899.313358*1000
20005810075.22
1003
Current for a Three-Phase Fault at Secondary Terminals of a Three-ϕTransformer (continued)
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Siemens Industry Inc., Siemens Power Technologies International 4-10
R = CIRCUIT RESISTANCE (POSITIVE SEQUENCE) IN OHMS
X = CIRCUIT REACTANCE (POSITIVE SEQUENCE) IN OHMS
VSMAG
= MAGNITUDE OF SENDING END Φ
TO NEUTRAL
VOLTAGE IN VOLTS
VRMAG
= MAGNITUDE OF RECEIVING END Φ
TO NEUTRAL
VOLTAGE IN VOLTS
I = MAGNITUDE OF LINE CURRENT IN AMPERES
Θ
= ANGLE BETWEEN SENDING END VOLTAGE VS
AND LINE CURRENT I
(POSITIVE FOR LAGGING POWER FACTOR LOADING)
)cossin(222222 RXIVXIRIVV SMAGSMAGRMAG
sincos XRIVV SMAGRMAG
EXACT EXPRESSION FOR RECEIVING END VOLTAGE MAGNITUDE (VRMAG
):
APPROXIMATE EXPRESSION FOR RECEIVING END VOLTAGE MAGNITUDE (VRMAG
):
CIRCUIT ANDSYMBOLS:
Expressions for Voltage Drop in Three-Phase Symmetrical Circuit with Balanced Loading
R XVS VR
I
VSI
O
RECEIVINGEND
SENDINGEND
-IR-IX
VR
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Siemens Industry Inc., Siemens Power Technologies International 4-11
VoltsV
RXIVXIRIVVoo
RMAG
SMAGSMAGRMAG
5.7395)84.25cos2.084.25sin6.0(250750526.02502.02507505
)cossin(222222
22222
VoltsV
XRIVVoo
RMAG
SMAGRMAG
6.739484.25sin6.084.25cos2.02507505
sincos
EXACT EXPRESSION FOR RECEIVING END VOLTAGE MAGNITUDE:
APPROXIMATE EXPRESSION FOR RECEIVING END VOLTAGE MAGNITUDE:
EXPRESSION FOR VOLTAGE DROP (difference between
magnitude of sending end voltage and
magnitude of receiving end voltage)
VoltsVVDROPVOLTAGE RMAGSMAG 11073957505
GIVENS:VSMAG
= 7505 VOLTSI = 250 AMPERESΘ
= 25.84 DEGREES
R = 0.2 Ω
X = 0.6 Ω
Expressions for Voltage Drop in Three-Phase Circuit with Balanced Loading (continued)
R XVS VR
I
VSI
O
RECEIVINGEND
SENDINGEND
-IR-IX
VR
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WAVEFORMS ON OSCILLOSCOPE
WAVEFORM ON SCREENIN DIFFERENTIAL MODE
)sin(*0.2
)180sin(*0.1
)sin(*0.1
21
2
1
oNN
ooN
oN
tVV
tV
tV
Voltage Relationships, 120/240 V Single-Phase Three-Wire Service
X1
X3
X2
H1
H2
INPUT1
INPUT2
DUAL CHANEL DIGITAL SCOPE
N
O1
O2
120 V
120 V 240 V
RMS VOLTAGES READWITH MULTI-METER
7505 V
DISTRIBUTIONTRANSFORMER
TERMINALS
D# 2005 BR, DUAL CHANEL SCOPE.FCW
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WAVEFORMS ON OSCILLOSCOPE
WAVEFORM ON SCREENIN DIFFERENTIAL MODE
)30sin(3
)120sin(*0.1
)sin(*0.1
ooNBNA
ooNB
oNA
tVV
tV
tV
Voltage Relationships, 120/208 V Three-Wire Network Service
X1
X3 X2
INPUT1
INPUT2
DUAL CHANEL DIGITAL SCOPE
N
OA
O B
120 V
120 V 208 V
RMS VOLTAGES READWITH MULTI-METER
NETWORK TRANSFORMERLV TERMINALS
OCD#2005 BR DUAL CHANEL SCOPE-2 FCW
X0
Note:
This gives the mathematical basis for the phase-to-phase voltage being √3 times the phase-to-neutral voltage in a balanced system
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•120/240 VOLT SINGLE-PHASE 3-WIRE •120/208 VOLT 3-WIRE NETWORK
FOUR TERMINALSOCKET
FIVE TERMINALSOCKET
ONE POTENTIALCOIL
TWOPOTENTIALCOILS
Self Contained Meters for 120/240 V Single-Phase Three-Wire Service & 120/208 V Three-Wire Network