Page 290 - Practical Power System and Protective Relays Commissioning

284 Practical Power System and Protective Relays Commissioning

MVA b 3 100 100 3 100
MVA F 5 5 5 1000MVA
Z% 10
MVA F 1000
If of HV side of Tr 5 5 5 2624A
O3 3 220 O3 3 220
1000
IF of LV side of Tr 5 5 8747A
O3 3 66
I set 5 600 A, CT 5 500/1
TM 5 0.4
PSM 5 8747 5 14:58
600
0:14
Relay operating time 5 T R 5
14:58 0:0221
T R 5 2.54
For a fault of 8747 A the operating time will be:
t.op 5 T R .TM 5 2.54 3 0.4 5 1.016 second
With a grading time step 5 0.4 second.
Then the operating time of R 1 should be more than 5 1.016 1 0.4 5 1.416
second.
Relay R 1 setting on the HV side of Tr
I F on HV side 5 2624 A
We can set the relay as follows: I set 5 1.45 3 I Tr HV side
MVA 250 3 10 3
I Tr HV side 5 p ffiffiffi 5 p ffiffiffi 5 656A
3 3 VHV 3 3 220
I set 5 1.45 3 656 5 951.2 A
2624
I Fault
PSM 5 5 5 2:76
I set 951:2
Set top 5 1.5 second, as seen above it should be more than 1.416 second.
Top 5 TM.T R
0:14
T R 5 0:0221 SI 2 Curve
2:76
TR 5 6.825
top 1:5
TM 5 5 5 0:219
T R 6:825
R 2 Setting
I set 5 600 A PSM 5 14.58 TM 5 0.4 CT 5 500/1
R 1 Setting
I set 5 951.2 A PSM 5 2.76 TM 5 0.219 CT 5 1000/1