distance protection power swing
DESCRIPTION
Distance protection and Power SwingTRANSCRIPT
TLQ2 - February 2003 Power Swing 1
Distance Protection
Power Swing
Gustav Steynberg
TLQ2 - February 2003 Power Swing 2
Power swing: Voltage diagram
LZS1
LZL
LZS2
E2 = E'2E1UA UB
U'B
U'A
'L L
' E'1
E1 E2ZS1 ZS2ZL
UAUB
Two Machine Problem
If the angle becomes too large, the system stability can be lost
TLQ2 - February 2003 Power Swing 3
Power swing locus and relay characteristic in the impedance diagram
E1 = E2
E1 > E2
E1 < E2
X
R
ZS2
B
ZL
A
ZS1
ZLoad
' load point
TLQ2 - February 2003 Power Swing 4
Power swing Apparent impedance at relay location
21 EE
21 EE
21 EE
equal
Power swing locus
TLQ2 - February 2003 Power Swing 5
Dynamic system stability, equal area criterion
ZS1
U1E1
U2E2ZS2
ZL
ZL
D PTP = · sinE1 · E2
XT
1
D
2
D
3
D
A
C
1
3
2
1
2
30
4
5
6
0
1
20 90° 180°
PT
P
B
TLQ2 - February 2003 Power Swing 6
56
1
34
X
RZload
ZS1
ZS1
ZL2
2
0
0
Power swing locus in the impedance plane
TLQ2 - February 2003 Power Swing 7
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 largeto avoid load encroachment (typ. 5 )
During fast swings the time available(t) for detection of impedance vectorin the power swing zone is too short. Z
t = time for transition of Z from outer to inner zone
TLQ2 - February 2003 Power Swing 8
Advanced Power swing blocking techniques (7SA513, 7SA522, 7SA6)
•Novel space vector based principle
•Self-setting
•Small Z (1 Ohm at In=5 A)
•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)
dZ/dt measurement
Calculation of swing centre and plausibility check (+90O< <-90O)
Stable swing
Unstable swing
ZX
R
TLQ2 - February 2003 Power Swing 9
Power Swing detection: New method
dR
dX
(k-n)
(k-n)
dR(k)dX (k)
Power swingX
R
Fault entry
Fault impedance
Loadimpedance
Transition from load to fault is fast
Power swing transition is slow
Continuos monitoring of the impedance trajectory
Monitoring of trajectory continuity Monitoring of trajectory velocity
Evaluation of trajectory ellipse
TLQ2 - February 2003 Power Swing 10
Example:
i/kA
t/ms500
u/kV
t/ms500
200
-3
6
3
R
A ZA a Zl b ZB B~ ~ ~ ~ ~
Evaluation of the power swing process
Power swing locus(EA>EB)
-90O
180O
0O
90OXm
Slip frequency
EBEA
Relay
Relay
TLQ2 - February 2003 Power Swing 11
Novel power swing detection provides secure operation with swing frequencies of up to 7 Hz
t/s0,2 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 1,6iL1/A-4-20
t/s0,2 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 1,6iL2/A-20
t/s0,2 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 1,6iL3/A-202
t/s0,2 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 1,6uL1/V-500
t/s0,2 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 1,6uL2/V-50050
t/s0,2 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 1,6uL3/V-50050
t/s0,2 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 1,6DisTRIP3p Z1BmfRelay TRIPRelay PICKUPDis. reverseDis. forwardDis.T.SEND>DisTel Rec.Ch1Power Swing
Example:400 kV400 kmfPS 2 Hz3-pole fault
TLQ2 - February 2003 Power Swing 12
Fault detection during power swing
I1
I2
V1
Trip
The Power swing passes throughthe trip characteristic several times.
Single phase fault is detected andcleared.
TLQ2 - February 2003 Power Swing 13
Three phase fault during Power Swing
Three phase fault during power swingis detected and cleared
Fault inception while swing is insidetrip characteristic
I1
V1
V2
V3
Trip