Hamilton Power Systems

8/8/2019 Hamilton Power Systems

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Copyright 2005 W.O. (Bill) Kennedy

Power Systems

for the

Non-Power Engineer

Hamilton Section

February 25, 2005

W.O. (Bill) Kennedy, P.Eng., FEIC

IEEE Canada President


1 23

56

7

8

50 MW

25 MVR

80 MW

40 MVR

205 MW

103 MVR

9 10 11

95.00 MW

1 MW

1 MVR

51.50 MW51.50 MW51.50 MW

6 .0 0 M VR 6 .0 0 M VR 1 1. 00 MV R

5.10 MVR

0.00 MVR

95.00 MW

1.02 pu

-4.62 Deg

0.99 pu

-11.01 Deg

1.06 pu-2.43 Deg

88.4 MVR


Purpose

Give you a basic understanding of what

power systems are and how the

components fit together and work

Concepts will be emphasized

Mathematics will be kept to a minimum

Mathematics only when necessary


2/25


Introduction

First part covers power system

components

Second part covers how the

components fit together and work

along with some measures of

power system performance


A little bit of Physics

Hans Christian Oerstead discovered therelationship between magnetism andelectricity

Michael Faraday discovered that avoltage is induced on a wire when it wasmoved in or through a magnetic field

James Clerk Maxwell developed themathematics of electromagnetics


Real and Reactive Power

Real power does the work

Reactive power helps real power

do the workPower systems need both or they

wont work

What is reactive power?


3/25


Reactive power

Quarterback can

throw a bullet, butnot very far

For long distances,throws in an arc

Real power is thebullet

Reactive power isthe height of the arc


Reactive Power Capacitors store energy equal

to CV2

Capacitor banks are used to

boost or raise voltage

Reactors use energy equal to

LI2

Motors and fluorescent lights

require reactive power


Part 1 - Equipment

Generators

Transformers

Transmission Lines

Loads


4/25


Generators


Generators

Fundamental Law

E = N d/dt

Where is the flux

Magnetic example

High school physics

Faraday's discovery motion

Maxwell mathematical theory


Generators

Rotor turns inside of the generator

satisfying Faradays Law

Voltage induced on the stator followsa sine wave

Take advantage of space and put three

coils equally spaced, 120o apart


5/25


GeneratorsThree Phase

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

0 45 90 135 180 225 270 315 360

Degrees

Magnitude

Phase A

Phase B

Phase C

Motion of rotor induces a voltage on the stator

Stator doesnt move and waveform reflects effect of

rotor field as it moves inside the machine


Generators

ControlTerminal voltage

Speed

Terminal voltage controlled by varyingthe voltage applied to the dc field of therotor

Speed controlled by governor, as loadincreases, fuel supply increases


Generators

Speed and frequency (60 Hz)

Frequency (f) = n/60 * p/2

Poles are in pairs, hence divide by 2

Speed in revolutions per minute, whereas

frequency in cycles per second, hence

divide by 60

Steam sets high speed, small rotors

Hydro sets low speed, big rotors


6/25


Generators

Two pole machine

rotates at 3600 rpm steam generator

Twelve pole

machine rotates at

600 rpm hydro set


GeneratorsGeneration by Fuel Type (Canada)

14%

53%

3%

10%2%

16%

2%

0%

coal

nuclear

hydro

oil

gas

dual fuel

pumped storage

other

Prime mover drives the generator

Energy sources in Canada


Generators

Capability curve

Limits

Stator heating

Rotor heating

Stability

Whats required

Whats used

Generator CapabilityCurve

-1

-0.8

-0.6

-0.4

-0.2

0

0.20.4

0.6

0.8

1

0.00 0.25 0.50 0.75 1.00

Real PowerReactivePower


7/25


Generator Capability Curve

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

0.00 0.25 0.50 0.75 1.00

Real PowerReactivePower


Transformers

Follow Faradays Law

E1=N1d/dt & E2=N2d/dt

Flux (d/dt) is constant

Voltage change depends on number of

turns, and basic equations can be

equated with the result:

E1/N1 = E2/N2


Transformers

Since conservation

of energy must be

preserved and

voltage variesinversely, current

must vary directly

I1N1 = I2N2


8/25


Transformers

Usual connection for the transmission systemis WYE grounded at the high voltage

Generators connected DELTA

Loads can be both


Transmission lines

Transmission lines are the highways onwhich power travels

Losses are proportional to the currentsquared on the line times the resistance

Want highest practical voltage tominimize losses

As we will see, SIL is an importantproperty of transmission lines


Surge Impedance Loading

(SIL)

Transmission line

consists of:

Shunt capacitance

Series resistance and

inductance

Distributed along length

of line

Treat as distributed

lumped elements

Can ignore resistance


9/25



(SIL)

Close the breaker at

sending end Shunt capacitance

charges to CV2

Close the breaker at

receiving end and feed

the load

Series inductance uses

energy at LI2

Load

Load



(SIL)

Equating shunt and series energies

CV2 = LI2

Performing the math yields

SIL (power) = V2/SI


Properties of Surge Impedance (SI)

Remains fairly constant over a wide range ofvoltages

Starts around 400 at lower voltages and

decreases with bundling to around 225 at1500 kV

Capacitance and inductance also remainconstant

Using this we can construct the followingtable


10/25


Properties of Transmission Lines

Voltage (kV) SI () R ( /km) X ( /km) Charging(kVAr/km)

SIL(MW)

X/R

69/72 370 0.4 0.5 15 13/14 1.2

138/144 370 0.2 0.5 70 50/55 2.5

230/240single

340 0.07 0.45 225 170 6

230/240bundled

300 0.07 0.4 290 180/195 6

345 bundled 285 0.026 0.365 525 415 14

500 bundled 250 0.018 0.345 1340 990 20


St. Clair Curve

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

2.75

3.00

3.25

100

200

300

400

500

600

700

800

900

1000

Length (km)

LineLoading

(SIL)


Loads

Three types of load models

Constant MVA motors

Constant current resistive loads Constant impedance reactor & capacitor

banks

For power flow use constant MVA

For transient studies need a combination and

may require frequency


11/25


Summary Part 1

Generators make the product

Transformers raise and lower voltageto allow efficient transport of product

Transmission lines are the highways

Loads are the end user of the product


Time for a BreakTime for a Break


Characteristics of power systems

Generation is usually remote from loads

Transmission needed to connect generationto load

Transformers needed to raise/lower voltage Want as high a voltage as practical fortransmission minimizes losses

Use load size, generator size and line SIL toget line voltage

In Saskatchewan, lines are typically 170 kmlong

At that distance loading 2 times SIL


12/25


Putting it all together

Generators produce real power (P)

Generators produce/consume

reactive power (Q)

Generator Q for underexcited

operation is around half overexcited

ability



Transmission lines consume P in formof losses, typically 5% to 7% ofgeneration

Lines produce/consume Q dependingon power flow on the line as a fractionof SIL< SIL VArs flow out of line

> SIL VArs flow into line

Half from each end, if voltages are equal



Loads consume P & Q

P required for resistive loads

Q required for reactive loads induction motors

Synchronous motors can produce/consume Q

Switching and/or load stations

Use shunt reactor/capacitor banks to

produce/absorb Q

Primarily for voltage control


13/25


Breakers

Breakers used toconnect/disconnect

equipment

Breakers must be

capable of picking

up and dropping

loads


Breakers

Breakers must becapable of switchingunloadedtransmission lines

Breakers must becapable ofinterrupting thesymmetrical faultplus any dc offset


How the power system works

Fundamental rules

Maintain reactive power balance and

voltages will be in required range typically +/- 5% of nominal

Maintain load/generation balance and

frequency or speed remains constant

typically 60 Hz +/- 0.02 Hz


14/25


Power flow

To solve a power flow need to solve for four

variables at each bus Bus voltage V

Bus angle

Real power P

Reactive power Q

However, some variables already known

Load P & Q

Generator bus V


Power flow

Need a model of the system

Per unit system is best

Must have consistent voltage ratios

Base impedances on voltage level

Most models involve some lumping, i.e.not practical to model every detail

However, this depends on the type ofstudy


Solution methods

Four solution methods

Gauss-Siedel solves vector equations

Newton-Raphson solve for P & Q by

separation of variables

dc solves circuit as a dc circuit by

treating jX as a resistance

Decoupled load flow variant of Newton-

Raphson. Separates V &


15/25


Solution methods

Solution results

Balance generation with load and lossesKeep all bus voltages within tolerance +/-

5%

Require a slack or swing bus. Can be afictitious generator to supply/absorb P & Q

Solution achieved when swing bus P & Qequal zero

Not practical, therefore minimize swing busP & Q


Types of studies

Steady state studies

Operations study effect today and

tomorrow, usually short time, e.g. up to

one month

Planning study effect of load and

generation three or more years in future

Fault study what happened yesterday


Types of studies

Dynamic studies

All of the above: Operations, Planning &Fault

Transients what happens as powersystem moves from one steady state toanother

Additional studies determine equipmentratings, e.g. breaker duty


16/25


Contingencies

Contingencies test the system for

robustnessContingency loss of one or more

components at a time

Costs escalate if system designed formore than two contingencies

Example loss of a generator and line ortransformer N-G-1 (NERC category C)


Power system example

1 23

56

7

8

50 MW

25 MVR

80 MW

40 MVR

205 MW

103 MVR

9 10 11

95.00 MW

1 MW

1 MVR

51.50 MW51.50 MW51.50 MW

6 .0 0 M VR 6 .0 0 M VR 1 1 .0 0 M VR

5.10 MVR

0.00 MVR

95.00 MW

1.02 pu

-4.62 Deg

0.99 pu

-11.01 Deg

1.06 pu-2.43 Deg

88.4 MVR


Power System Performance

WAMS Wide Area MeasurementSystems

Losses weve ignored losses upto this point

Measuring outages

Lines & Stations

Delivery Point measures


17/25


WAMS

Slow speed synchronized

measurements of voltages, power andfrequencies on a power system

IEEE Standards PC37.118 in votingstage

Want to capture slow-speed events

High-speed events captured by faultrecorders


Synchrophasor Standard

PC37.118 Standard defines measurement, accuracy & test

requirements (includes timing requirements)

Phasor

Measurement

Unit (PMU)

UTC Time

(GPS)

X(n) = Xr(n) +jXi(n)X = Xr +jXi

X

Xi

X r

X(n)

Xi(n)

X r(n)

Phasor defined

at t = 0.

Waveform matchesphasor definitionat t = 0.

PMU estimates phasorequivalent from an intervalof the waveform.

The estimate is comparedwith the defined phasor todetermine error (TVE).

= [((Xr(n) - X

r) 2 + (X

i(n) - X

i) 2 ) / (X

r

2 + Xi

2 )]-1

-0.5

0

0.5

1

- 0. 01 2 - 0. 00 8 - 0. 00 4 0 0 .0 04 0 .0 08 0 .0 12


Phasor Systems in WECC PMU to PDC, real time

BPA - 15 in NW, 1 in CAL

SCE - 14 in S. CAL &NEV

PG&E - 6 in N. CAL

PNM - 2 in NM

WAPA - 3 in COLO & NM

BC Hydro - 6 in BC

APS/SRP - 5 in AZ & NM

PMU to stored files Alberta ISO - 4 in Alberta

2nd Level, PDC-PDC SCE -BPA

WAPA - BPA

BPA & SCE to Cal ISO


18/25


19/25


S u m m a r y P lo t F o r 0 2 1 0 0 8 N W G e n D r o p _ A l l A n g s

0 2 1 0 0 8 N W G e n D ro p _ A llA n g s 1 2 / 1 3 /0 2 _ 1 2 :5 9 :1 2

S Y L M S y l m a r B u s V o l t a g e V A n g R M F 0 1

A U L T 3 4 5 k V B u s V o l t a g e ( C r a i g ) V A n g R M F 0 2

B E A R 3 4 5 k V B u s V o l t a g e ( C r a i g ) V A n g R M F 0 2

S H I P 3 4 5 k V B u s V o l t a g e ( S a n J u a n ) V An g R M F 0 2

I N G 1 5 L 5 2 C u s t e r V o l t a g e V A n g R M F 0 3

D M R 1 5 L 2 9 M a l a s p i n a V o l t a g e V A n g R M F 0 3

N I C 1 5 L 8 1 I n g l e d o w V o l t a g e V A n g R M F 0 3

A B 0 1 C a l g a r y V A n g R M F 0 4

P i n n a c l e P k B u s V A n g R M F 0 5

0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5- 2 0 0

- 1 0 0

0

10 0

20 0

30 0

40 0

T i m e i n S e c o n d s s i n c e 0 8 - O c t - 2 0 0 2 2 2 : 3 1 : 1 5 . 5 3 1

S y l m a r

BC H

C a l g a r y

P i n n a c l e P k

S h i p r o c k

A u l t / B e a r s E a r s

D M W G / j f h


Chief Joseph dynamic brake 1400 MW

toaster

Three 230 kVstructures

Resistive wirestrungthroughpulleys

Limited timeduration .5 sec

normal

2 sec limit

Cool-offrequired


Dynamic brake detail

Lower

brackets with

pulleys and

weights for

tension

Pulley section

adjusts for

ambient and

loading

temperature

changes


20/25


RAS initiated

Dynamic

Brake

Faulted PT causesbus outage

RAS triggers Brake Low Volt

Power flow drop

No gen drop initiated

Long fault causesmore significantringdown networkresponse

No net systemeffects


Transmission Losses

Transmission Losses

0

100

200

300

400

500

4 75 0 5 00 0 5 25 0 5 50 0 5 75 0 6 00 0 6 25 0 6 50 0 6 75 0 7 00 0 7 25 0 7 50 0 7 75 0

NetGeneration toSupply Alberta Load(MW)

Losses

(M

W

)

Losses are

stochastic

Simple system

losses vary as a

square of current

Complex system

losses display a

linear variance


Transmission LossesTransmission Losses Histogram

0

100

200

300

400

500

197

210

223

236

249

262

275

288

301

314

327

340

353

366

379

392

405

418

431

Losses (MW)

Coun

t

Histogram demonstrates a normal

distribution pattern for losses


21/25


Transmission lossesTransmission Generation, Load and Losses by Day

4000

4500

5000

5500

6000

6500

7000

7500

1 2 3 4 5 6 7 8 9 1 0 11 12 13 14 15 16 17 18 1 9 20 21 22 2 3 24

Hour

Geenration&Load(MW)

0

100

200

300

400

500

600

700

800

900

1000

Losses(MW)

Net Gen

Net Load

Losses

+3-sigma-3-sigma

Ave Losses

Losses on AIES are very l inear


Power system performance

Need measure system performance

Measure frequency and duration ofoutages

Reason outages occur infrequently

Measures of performance look at allcomponents and causes

Usually stated as an average of wholesystem


Performance

For Alberta, AESO publishes data to itswebsite on line and terminal outages asan overall average for the voltage class

For Delivery Points frequency andduration data also published as asystem average

For comparison, all Canada data isincluded for Delivery Points


22/25


Performance

Two types of duration are measured

Momentary < 1 minute

Sustained > 1 minute

Following are examples of charts

published on the AESO website

http://www.aeso.ca/transmission/5548.html


Transmission - line

1.721,7010.05%6.074,5980.7675798,997Total

5.96950.03%2.64370.88141,595500

0.943200.04%4.931,1590.6923533,968240

1.266850.05%7.062,2720.5932254,417138/144

6.676010.14%6.081,1302.061869,01769/72

Frequency

per 100 km.a(faults/100

km.a)

Number ofMomentary

Faults

Unavailabilityper 100 km.a

(%)

Average

OutageDuration(hrs/fault)

Total

OutageDuration(hours)

Frequency

per 100 km.a(faults100

km.a)

Number ofSustained

Faults

KilometerYears(km.a)

VoltageClass (kV)

For the Period From 1997 - 2001

Summary for Line Related Forced Outages

Transmission Outage Statistics

Alberta Interconnected Electric System


System Average Interruption Frequency

SAIFI-MI

0.0

0.4

0.8

1.2

1.6

1 997 1 99 8 1 99 9 2 00 0 2 00 1

Year

Frequency

Alberta

Canada

Ice StormRemoved


23/25


System Average Interruption Duration

SAIDI

0

100

200

300

400

1 997 1 998 19 99 20 00 20 01

Year

Duration(minutes) Alberta

Canada

Ice StormRemoved


Summary

Generators make the product

Transformers raise and lower thevoltage and current to allow efficienttransport of the product

Transmission lines are the highwaysthat allow the power to flow from thegenerator to the load

Loads are the end user of the product


Summary Part 2

Power flow studies model and test

the system for robustness

yesterday, today and tomorrowN-G-1 (NERC C) is used to test

the system for operation today and

into the future


24/25


Summary Part 2

Losses are an important part of

power system design and operation

Higher voltage lines reduce losses

However, losses are fixed when the

conductor is chosen

Must do a conductor optimization

study


Summary Part 2

Outages are measured using

frequency and duration techniques

Presented as system average

numbers


Summary

Power systems are mankinds most complex

machine

Power systems cover thousands of square

kilometers Supply thousands of customers all day -

everyday

Must always work together generally do

Must supply power and energy when

requested ultimate Just in Timesystem


25/25


Thats all folks!

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