Armando Guzman

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Copyright © SEL 2004

Local and Wide-Area

Network Protection SystemsImprove 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 of

Wide-Area System Disruptions

l Voltage collapse

l Rotor angle instability



Voltage Collapse Per Carson Taylor

“A power system at a given

operating state and subject to a

given disturbance undergoes voltage

collapse if post-disturbance equilibriumvoltages are below acceptable limits”

Power System Voltage Stability , EPRI,

ISBN 0-07-063184-0



Generation ≠ Load DuringTransient Angle Instability

Generators cannot deliver their totaloutput power to the system



Voltage Collapse Evolves

Into Angle Instability

0.1 0.2 0.3 0.4 0.5 0.6 0.7

Time (s)

V

o l t a g e ( p u

)

-0.8

-0.4

0

0.4

0.8



Slow Fault Clearing Time

Initiates Voltage Collapse

Zone

2

Zone

2

Zone

2

51

51

Restof Power

System





Out-of-Step Detection Logic

Avoids Zone 1 Tripping



Transmission Line Tripping

During System Oscillation in Idaho



Wide-Area Protection Systems

Protection systems to minimize risk

of wide-area disruptions and increasesystem power transfer capability



Wide-Area Network Undervoltage

Load-Shedding Scheme (BC Hydro)

Rest of Power

System

Load Load

Load

Area

1

U/V

Area

2U/V

U/V

Area 3



U/V Load Shedding Is Enabled

Only if Synchronous Condenser

Output Is Close to Rated Output

t1

MVAR Output Close to Rated

U/V

Shed

Block 1

Area 1

Area 2

Area 3

Area 3

Synch

Cond

AND

1

AND

2

OR

1 AND

3

t2

t3

Shed

Block 2

Shed

Block 3

U/V

U/V



Area 2 Generation Depends on System

Real-Time Transmission Capability (CFE)

Area 1

Heavy

Load

Real Power andOpen Line Monitor

Area 3

Light

Load

Area2

Line 1

Line 2Line 3



Scheme Sheds Generation When

Two Lines Open and P > 1100 MW

Line 1

Line 2

Line 3

Two

Lines

Open

1100 MW

And

Trip ExcessGeneration

in Area 2

Line Open

Σ

–

+

Line Open

Line Open

MW

MW

MW



Wide Area Protection Schemes

in the Western United StatesKemano

Colstrip

Malin

John Day

Peace River

Midpoint

Jim Bridger

IPP

Captain

Jack

Grand

CouleeChief

Joseph

Four Corners

Tesla

San

Onofre

Palo Verde



Enhance Power Transfer Through

Wide-Area Network Protection (US)

L i n e

3

L i n e

2

L i n e

1North Intertie

South Intertie

East Intertie

Area 4 Area 1

Real Power and

Open Line Monitor

Area 2 Area 3

Real Power

Monitor Line 4

Line 6Line 5

L i n e 7

L i n e 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

II

I

V

IV III

I,II V

No Actions

in Area 2900

0

3675



Set IV Actions for Three-Line-Open

Condition Between Area 1 and Area 2l 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 Drop

Below the 95 Percent Threshold for

Two-Line Loss Between Buses 6 and 7

0 5 10 15 20 25 30

V

o l t a g e

( p u )

Seconds

0.8

0.9

1

0.95 Bus 8

Bus 9

Threshold



Inverse-Time Undervoltage Elements

Shed Low-Voltage Loads First

0.2 0.4 0.6 0.8

Voltage (pu)

S e c o n d

s

0

5

10

15



Bus 8 Voltage Recovers After

the ITUV Element Drops the Bus 9 Load

0 5 10 15 20 25 30

V o l t a g e (

p u )

Seconds

0.8

0.9

1

1.1

Bus 8

Bus 9



Synchronized Phasor Measurements

in the Western United States



Synchronized Phasor

Measurement System at BPA

PMU

PDC

StreamReader

display and recording

Direct data

exchange 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 and

reactivestability

Inter-area

angle limits



StreamReader Application



Wide-Area Protection / Control Using

Synchronized Phasor Measurements

PDC(data concentrator

that inputs

and correlates

phasor data)

SVC

WACS Controller

(calculations,

outputs)

Wideband data output by Ethernet

Digital outputs to

WAPS controller

WAPS Controller

(access to

trip circuits)

Dynamic Brake

Generator Trip

PMU

PMU

PMU



Voltage Swing for a Double

Palo Verde Outage (2700 MW)

V

o l t a g e ( p

u )

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 Loss

in Northeast Washington

F r e q u e n c y D e

v i a t i o n F r o m N

o m i n a l - m H z

51 52 53 54 55 56 57

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

Malin

Grand

Coulee

Vincent

–.020 Hz

0.9 s

0

–20

–40

–60



Grand Coulee Frequency,

Coulee-Vincent Phase Angle,

Los Angeles Generator Output

54

Generator Output

in Los Angeles Area

Phase Angle FromCoulee to Vincent

Initial

Fault

Grand Coulee

Frequency

m

H z

/ D e g r e e s

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

51 51.5 52 52.5 53 53.5

90

80

70

60

50

40

30

20



1400 MW Dynamic Brake

at 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 minimizerisk of system disruptions and increase

power transfer capacity



Conclusions (2)

l Time-synchronized measurementsimprove power system dynamics

assessment

t They can be used for analysis and controls

l Inverse-time undervoltage elements

optimize load shedding to prevent system

voltage collapse without communications!

Armando Guzman

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