2012-2013 Distribution Systems Engineering Course for Con

© 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

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Inc., Siemens Power Technologies International 0-2

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


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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Siemens Industry Inc., Siemens Power Technologies International 1-4

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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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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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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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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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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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


Tab 2 -

Overview of Power Systems Distribution Systems Engineering –

Course 1

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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)


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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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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


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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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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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


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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

http://gocalifornia.about.com/bl_nvhdamphoto_work.htm

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HYDRO ELECTRIC GENERATORS ROTATE AT MUCH LOWER SPEED THAN GENERATORS POWERED WITH STEAM TURBINES AND GAS TURBINES.

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• 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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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


• 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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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


COMPRESSORSECTION

COMBUSTIONCHAMBER

SHAFT FORCONNECTIONTO GENERATOR

TURBINESTAGE

EXHAUST

AIRINPUT

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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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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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Generation Plant, Step-Up Transformers and Transmission Lines

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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


THREE-PHASE OIL-FILLEDPIPE-TYPE CABLE

SINGLE-CONDUCTOR SOLIDDIELECTRIC POWE CABLE

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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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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


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 )


Tab 3 - Overview and Introduction to Distribution Systems Distribution Systems Engineering –

Course 1

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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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Typical Utility Power System Generation, Transmission, Distribution

GEN

GEN

TRANSMISSION SYSTEMPOWERPLANT

N.O.


POWER PLANTSUBSTATION

TRANSMISSIONSUBSTATION

DISTRIBTION PRIMARYFEEDER


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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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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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


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


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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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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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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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.


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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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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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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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.



P

P

N.O. = NORMALLY OPENN.C. = NORMALLY CLOSED

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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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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)


• 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


TIE SWITCH (TS)NORMALLY OPEN (N.O.)

FEEDER 1

FEEDER 2

OPEN

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• 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)


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



FEEDER 1

FEEDER 2

OPEN

FAULT

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• 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


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



FEEDER 1

FEEDER 2

CLOSED

FAULT

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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.


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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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


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


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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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


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.


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


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



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



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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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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PARALLELING BUS FOR THREE NETWORK TRANSFORMERS / PROTECTORS

CABLES TO NETWORK PROTECTORS

SILVER-SANDCABLE LIMITERS

NWK XFR. &NWP.

NEUTRAL BUSINSULATED PHASE BUSES

CABLES TOCUSTOMERSERVICEEQUIPMENT


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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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SINGLE-CONDUCTORPRIMARY CABLESAND SPLICES

GROUNDING SWITCHOPERATING HANDLE

NETWORK TRANSFORMER IN SIDEWALK VAULT

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• 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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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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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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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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• MICRO PROCESSOR NETWORK PROTECTOR RELAYControls automatic operation of network protector (tripping and closing)

LED STATUSINDICATORS

TERMINALS FOR CONNECTIONS TONETWORK PROTECTORCONTROL WIRING


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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.


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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


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


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


3

NETWORKSUBSTATION

FEEDER BREAKERS

CABLELIMITER

NETWORK UNIT

LV CABLES

PRIMARY

P + jQ3-P 4-W LOAD


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



N.C.BUSTIE

N.C.BUSTIE


3-4

P + jQ

P + jQ


LVNET105-A-H-FLT.FCW, 0.165X



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


3

NETWORKSUBSTATION

FEEDER BREAKERS

CABLELIMITER

NETWORK UNIT

LV CABLES

PRIMARY

P + jQ3-P 4-W LOAD


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



N.C.BUSTIE

N.C.BUSTIE


3-4

P + jQ

P + jQ


LVNET105-C-H.FCW, 0.165X



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


3

NETWORKSUBSTATION

FEEDER BREAKERS

CABLELIMITER

NETWORK UNIT

LV CABLES

PRIMARY

P + jQ3-P 4-W LOAD


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



N.C.BUSTIE

N.C.BUSTIE


3-4

P + jQ

P + jQ


LVNET105-D-H.FCW, 0.165X



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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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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• 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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• 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


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• 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


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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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• SILVER-SAND CABLE LIMITER FOR 500 KCMIL SECONDARY CABLES

SPADETERMINALFOR BOLTINGTO BUS

COMPRESSIONTERMINAL FORCABLE CONDUCTOR

SILVER FUSIBLEELEMENT

M-SPOT TO AIDLOW-CURRENT CLEARING


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• FUSIBLE CRABS IN MANHOLE FOR CONNECTING & FUSING LV CABLES FIVE-WAY BY FIVE-WAY CRABS

NEUTRALS


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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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• CONVENTIONAL 216 VOLT CABLE LIMITER (LUG LIMITER)

RUBBER BOOTSPADETERMINAL FORBOLTING TOBUS BAR

CABLE RECEPTACLE FUSIBLE SECTION

ENCLOSURE TO ABSORBE HEAT ANDPREVENT CABLE MOVEMENT FOLLOWINGMELTING


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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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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


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• 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


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VAN WITH INSTRUMENTATION FOR MEASURING CURRENT SPLIT IN LOW-VOLTAGE CABLES


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• COVERS FOR MANHOLES WITH PRIMARY AND SECONDARY CABLES

SLOTTED COVER SOLID COVER

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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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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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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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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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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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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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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


Distribution Feeders

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• Typical Feeder Layout (Radial)

• Voltage levels

• Loading

• Equipment

• Conductor Arrangements/Grounding

Overview

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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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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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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 -


For 35kV -


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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


SOURCESUBSTATION


SOURCESUBSTATION


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.


Examples of Distribution Primary Conductor Arrangements

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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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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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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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• 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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• 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


Questions?


Tab 4 Some Basic Relationships Distribution System Engineering -

Course 1

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Siemens Industry


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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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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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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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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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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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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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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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


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

Documents

2012-2013 Distribution Systems Engineering Course for Con