Copyright © SEL 2004

Local and Wide-AreaNetwork Protection Systems

Improve Power System Reliability

A. Guzman

D. Tziouvaras

E. O. Schweitzer

Schweitzer Engineering Laboratories, Inc.

K. E. Martin

Bonneville Power Administration

Power System Challenges

l Load-generation separation

l Environmental restrictions (NIMBY)

l Limited network growth

l Network resource optimization

l Separate companies for G,T,D

Main Causes ofWide-Area System Disruptions

l Voltage collapse

l Rotor angle instability

Voltage Collapse Per Carson Taylor

“A power system at a givenoperating state and subject to a

given disturbance undergoes voltage collapse if post-disturbance equilibrium voltages are below acceptable limits”

Power System Voltage Stability, EPRI,

ISBN 0-07-063184-0

Generation ≠ Load DuringTransient Angle Instability

Generators cannot deliver their total output power to the system

Voltage Collapse EvolvesInto Angle Instability

0.1 0.2 0.3 0.4 0.5 0.6 0.7Time (s)

Vo

ltag

e (p

u)

-0.8

-0.4

0

0.4

0.8

Slow Fault Clearing TimeInitiates Voltage Collapse

Zone2

Zone2

Zone2

51

51

Restof PowerSystem

Reverse Zone 3 Element Operated During Low Voltage Conditions

X

R

Overload

Out-of-Step Detection LogicAvoids Zone 1 Tripping

Transmission Line TrippingDuring System Oscillation in Idaho

Wide-Area Protection Systems

Protection systems to minimize riskof wide-area disruptions and increase

system power transfer capability

Wide-Area Network Undervoltage Load-Shedding Scheme (BC Hydro)

Rest ofPowerSystem

Load Load

LoadArea

1U/V

Area2

U/V

U/VArea 3

U/V Load Shedding Is EnabledOnly if Synchronous Condenser Output Is Close to Rated Output

t1

MVAR Output Close to Rated

U/V

ShedBlock 1

Area 1

Area 2

Area 3

Area 3SynchCond

AND1

AND2

OR 1 AND

3

t2

t3

ShedBlock 2

ShedBlock 3

U/V

U/V

Area 2 Generation Depends on System Real-Time Transmission Capability (CFE)

Area 1HeavyLoad

Real Power andOpen Line Monitor

Area 3LightLoad

Area2

Line 1Line 2Line 3

Scheme Sheds Generation WhenTwo Lines Open and P > 1100 MW

Line 1

Line 2

Line 3

TwoLinesOpen

1100 MW

AndTrip ExcessGenerationin Area 2

Line Open

Σ–+

Line Open

Line Open

MW

MW

MW

Wide Area Protection Schemesin the Western United States

Kemano

Colstrip

Malin

John Day

Peace River

Midpoint

Jim Bridger

IPP

CaptainJack

GrandCoulee

ChiefJoseph

Four Corners

Tesla

SanOnofre

Palo Verde

Enhance Power Transfer Through Wide-Area Network Protection (US)

Line

3Li

ne 2

Line

1North Intertie

South Intertie

East Intertie

Area 4Area 1

Real Power andOpen Line Monitor

Area 2 Area 3

Real PowerMonitor

Line 4

Line 6Line 5

Line

7

Line

8

Pacific NW

PG&E SCE

Inter-Area Power Flow Determines Set of Actions to Avoid Disruption

0-1500

A2 to A3(MW)

A2 to A1(MW)

I,II

IV

III

V

IV III

I,II V

No Actionsin Area 2

900

0

3675

Set IV Actions for Three-Line-Open Condition Between Area 1 and Area 2

l Area 2 informs Area 1 of line-open conditions in the intertie

l Pacific NW WAPS trips generation

l System separates into north and south networks

l System sheds pump load in Area 2

l Resistor dynamic brake inserted at Area 1

Model to Study Voltage Stability(Kundur, Power System Stability and Control)

11

1

10

Open

Open

5

2

376

8

9

Z=Constant

P=1692 MWQ=485 MVAR

P=207 MWQ=58 MVAR

Z=Constant

I=Constant

P=3844 MWQ=1194 MVAR

Voltages for Buses 8 and 9 DropBelow the 95 Percent Threshold for

Two-Line Loss Between Buses 6 and 7

0 5 10 15 20 25 30

Vol

tage

(pu

)

Seconds0.8

0.9

1

0.95Bus 8

Bus 9

Threshold

Inverse-Time Undervoltage Elements Shed Low-Voltage Loads First

0.2 0.4 0.6 0.8Voltage (pu)

Sec

onds

0

5

10

15

Bus 8 Voltage Recovers Afterthe ITUV Element Drops the Bus 9 Load

0 5 10 15 20 25 30

Vol

tage

(pu)

Seconds0.8

0.9

1

1.1Bus 8

Bus 9

Synchronized Phasor Measurements in the Western United States

Synchronized PhasorMeasurement System at BPA

PMU

PDC

StreamReaderdisplay and recording

Direct dataexchange withother utilities

Phasor DataConcentrator

(PDC)

SCADA

Data storage

Analog datameasurement–substations

Data inputand management

–control center

Other displays

Operation monitors–display and alarms Real-time

system controls

PMU

PMU

PDC

Voltage andreactivestability

Inter-areaangle limits

StreamReader Application

Wide-Area Protection / Control UsingSynchronized Phasor Measurements

PDC(data concentrator

that inputsand correlatesphasor data)

SVC

WACS Controller(calculations,

outputs)

Wideband data output by Ethernet

Digital outputs toWAPS controller

WAPS Controller(access to

trip circuits)

Dynamic Brake

Generator Trip

PMU

PMU

PMU

Voltage Swing for a DoublePalo Verde Outage (2700 MW)

Vol

tage

(pu)

CouleePearl

JohnDay

Olinda

Malin

Seconds

Tuesday, June 03 13:56:56 2003

200 2 4 6 8 10 12 14 16 18

1.2

1.10

1.00

0.90

0.80

Response to 750 MW Lossin Northeast Washington

Freq

uenc

y D

evia

tion

From

Nom

inal

- m

Hz

51 52 53 54 55 56 57

Seconds - starting at 15:41:44 on 7/7/99

Malin

GrandCoulee

Vincent

–.020 Hz

0.9 s

0

–20

–40

–60

Grand Coulee Frequency,Coulee-Vincent Phase Angle,

Los Angeles Generator Output

54

Generator Outputin Los Angeles Area

Phase Angle FromCoulee to Vincent

InitialFault

Grand CouleeFrequency

mH

z/D

egre

es

Seconds - starting at 15:41:44 on 7/7/9951 51.5 52 52.5 53 53.5

90

80

70

60

50

40

30

20

1400 MW Dynamic Brakeat Chief Joseph Substation

Conclusions (1)

l Use breaker failure together with direct transfer trip instead of Zones 2 and 3 for backup protection

l Timely, appropriate actions are required to avoid system disruptions

l Wide-area protection systems minimize risk of system disruptions and increase power transfer capacity

Conclusions (2)

l Time-synchronized measurements improve power system dynamics assessmentt They can be used for analysis and controls

l Inverse-time undervoltage elements optimize load shedding to prevent system voltage collapse without communications!