Siemens - Distance Protection Power Swing

Distance Protection Power Swing Power Transmission and Distribution

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Siemens AG 2006

Power swing: Voltage diagram

LZS1

Two Machine Problem E1

E2 ZL

ZS1

LZS2 E2 = E'2

E1

UA

ZS2

UB U'B

UB

UA

LZL

U'A E'1



'

'L

L

If the angle becomes too large, the system stability can be lost ©

Page 2

Symmetrical Components

Siemens AG 2006 Power Transmission and Distribution

Power swing locus and relay characteristic in the impedance diagram

E1 > E2

X

ZS2

B

E1 = E2

ZL

'



load point

A

R ZLoad

E1 < E2 ZS1

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Page 3

Symmetrical Components

Siemens AG 2006 Power Transmission and Distribution

Dynamic system stability, equal area criterion U1

E1

U2

ZL

ZS2

ZS1 D

1

E2

E1 · E2 PTP =

ZL

· sin

XT

5

P 3 3 4 B

0 PT A

C

6 1 D

2 2

2

1 0

0

D

1

90°

2

180° 

3 D ©

Page 4

Symmetrical Components

Siemens AG 2006 Power Transmission and Distribution

Power swing locus in the impedance plane

X ZS1

1

2 ZL 2

6

4 5

3 0 0

ZS1

R

Zload

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Page 5

Symmetrical Components

Siemens AG 2006 Power Transmission and Distribution

Power swing detection: Classic Method (Not used in 7SA52 and 7SA6)

Classic power swing detection is restricted to slow swings The setting of Z may not be too large to avoid load encroachment (typ. 5 )

Z

During fast swings the time available (t) for detection of impedance vector in the power swing zone is too short.

t = time for transition of Z from outer to inner zone

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Page 6

Symmetrical Components

Siemens AG 2006 Power Transmission and Distribution

Advanced Power swing blocking techniques (7SA513, 7SA522, 7SA6)

•Novel space vector based principle

Unstable swing X

•Self-setting •Small Z (1 Ohm at In=5 A)

Z

•Blocking up to high slip frequencies (7 Hz) •Recognition of all fault types during swing •Remains effective during single pole ARC open time (3-phase set-up)

R

 dZ/dt measurement

Stable swing

 Calculation of swing centre and plausibility check (+90O<  <-90O)

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Page 7

Symmetrical Components

Siemens AG 2006 Power Transmission and Distribution

Power Swing detection: New method

X

Power swing

Fault impedance

Transition from load to fault is fast

dR(k -n)

Fault entry

Power swing transition is slow

dX (k-n) dX (k )

d R(k)

Load impedance R



Continuos monitoring of the impedance trajectory



Monitoring of trajectory continuity



Monitoring of trajectory velocity



Evaluation of trajectory ellipse ©

Page 8

Symmetrical Components

Siemens AG 2006 Power Transmission and Distribution

Evaluation of the power swing process A EA

~

ZA ~

a

Zl ~

b

ZB ~

B

~

EB

0O

Power swing locus(EA>EB)

Relay Example:

Slip frequency

i/kA 6

-90O

3 500

-3

90O

Xm

t/ms

u/kV 200

500

t/ms

180O

Relay

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Page 9

Symmetrical Components

R

Siemens AG 2006 Power Transmission and Distribution

Novel power swing detection provides secure operation with swing frequencies of up to 7 Hz iL1/A 0 -2

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

1,3

1,4

1,5

1,6

t/s

-4

iL2/A

Example: 400 kV 400 km fPS  2 Hz 3-pole fault

0 -2

t/s

iL3/A 2

t/s

0 -2

uL1/V 0 -50

t/s

uL2/V 50 0 -50

t/s

uL3/V 50 0 -50

t/s

Power Swing >DisTel Rec.Ch1 Dis.T.SEND Dis. forward Dis. reverse Relay PICKUP Relay TRIP DisTRIP3p Z1Bmf t/s

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Page 10

Symmetrical Components

Siemens AG 2006 Power Transmission and Distribution

Fault detection during power swing

I1

I2

The Power swing passes through the trip characteristic several times.

V1

Single phase fault is detected and cleared.

Trip

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Page 11

Symmetrical Components

Siemens AG 2006 Power Transmission and Distribution

Three phase fault during Power Swing

I1

V1

V2

Three phase fault during power swing is detected and cleared

V3

Fault inception while swing is inside trip characteristic

Trip

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Page 12

Symmetrical Components

Siemens AG 2006 Power Transmission and Distribution