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An Out-of-Step Event in thePeruvian Power System

Yofre JacomeCOES SINAC

Peru

Western Protective Relaying Conference

October, 2007

Charles HenvilleHenville Consulting

Inc.

Presented by

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Overview

Background on loss of stability

Impact on system voltages

Differential or distance protection

October 2002 Event

Disturbance records

Actions since the disturbance

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Relevant factors

Voltage fluctuations

Limitations of differential protection

systems

Benefits of modern multifunction relays

Reasons for operating limits

Benefits of remedial action schemes

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Weak interconnections

System A

Y MVASystem B

Z MVA (Z>Y)

Weak tie

(Rated capability

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Example system

Line ALine B

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Equal area criterion (stable)

0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150

Angle (Degrees)

Power(PU)

Pre-faultPost-fault

Fault

Acceleration

area

Decceleration

area

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Damped recovery oscillations

0

50

100

150

200

0 1 2 3 4 5

time (s)

Angle(Degrees)

Oscillations leading to

stable equilibrium

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0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150Angle (Degrees)

Power(PU)

Pre-faultPost-fault

Fault

Acceleration

area

Deccel'n.

area

Equal area criterion (unstable)

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Angular separations of sources

0

50

100

150

200

0 1 2 3 4 5

time (s)

Angle(Degrees)

Loss of synchronism

Oscillations leading to

stable equilibrium

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Voltage Oscillations

d

P

Electrical Center

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WECC Planning Standards

Fi ure W-1 From NERC/WECC Plannin Standards

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d

P1

P2

P3

P1 : Steady state stability limit

P2: Transient stability limitP3 : Loss of synchronism

Relay response to out of step conditions

Distance Relays

Differential relays see no fault!

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Controlled Separation

100 MW

50 MW

Grid

70 MW 30 MW 40 MW

Electrical Center

Controlled separation point

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Frequency changes

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An out-of-step event

At 13:09 hours on 22 October, 2002

In the South Eastern Region of Peru

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South

Eastern

Area

System

Diagram

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FAUL

T

FAULT

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Event record from faulted line

(L-1008)

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Moquegua Terminal of L-2030

Trigger10/09/2002

01:09:06 PM.380

t/s-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

IR R

-10

0

10

t/s-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

IS R

-10

0

10

t/s-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

IT R

-10

0

10

t/s-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

VR R

-50

0

t/s-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

VS R

-50

0

t/s-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

VT R

-50

0

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Comparison of out-of-step voltages

t/s17.8 17.9 18.0 18.1 18.2 18.3 18.4 18.5 18.6

K2:Va a_1/V

-50

0

50

K1:VR R

-50

0

50

Tintaya V max 1.07 pu

Moquegua V max 1.00 puMoquegua

V min 0.85 pu

Voltage in phase

Maximum voltage

Voltage out of phaseMinimum voltage

Tintaya V min 0.53 pu

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62 Seconds of asynchronous

interconnection

Trigger10/09/2002

01:09:06 PM.380

t/s10 20 30 40 50 60

IR R

-10

0

10

t/s10 20 30 40 50 60

IS R

-10

0

10

t/s10 20 30 40 50 60

IT R

-10

0

10

t/s10 20 30 40 50 60

VR R

-50

0

t/s10 20 30 40 50 60

VS R

-50

0

t/s10 20 30 40 50 60

VT R

-50

0

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Frequency Divergence

South-eastern

Frequency

SEIN Frequency

Underfrequency

load shedding

in SEIN

Machupicchu

Generator trip

Generation

plant trip

(by operator)

SE Area

load loss

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Actions following the event

Impose operating limits

Replaced some protections with new

systems including out of step blockingand tripping

Replaced some power system

stabilizers

Implemented generation shedding RAS

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Operating Limit Nomograph

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Two different system responses

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Conclusions

Weak interconnections are exposed to out of

step conditions

Out of step conditions should be avoided but, if

they happen:

Systems should be separated in a controlled manner

Load and generation should be balanced in

separated regions

Re-synchronization might happen, but it might

not!

Real life events validate system models

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Questions?