5.4.4 Timing Test:
Most important test of any protection overcurrent relay is Timing Test, Timing test means you need to access relay’ s Time current characteristics Let suppose you have same system as you mention in pick up test
Section
Rating( MVA)
Power Grid 20 Transfor mer 1- 33KV 10 Transfor mer 1- 11KV 10 Transfor mer 2- 11KV 1
Short circuit MVA
Voltage level( KV)
117.647 0588 33
142.857 1429 33
142.857 1429 11
17.3913 0435 11
Full load current( Ir)
349.9195 185
174.9597 593
524.8792 778
52.48792 778
Short Circuit Current
2058.350 109
2499.425 132
7498.275 397
912.8335 265
Pick up 1.15 044 2 1.18 181 8 1.18 181 8 1.18 181 8
Instant aneou s Setting( 8 * Pic k up)
9.2035 39823
9.4545 45455
9.4545 45455
9.4545 45455
Earth Fault Pick up 1.017 69911 5 1.045 45454 5 1.045 45454 5 1.045 45454 5
Instant aneou s Earth Fault Pick up
8.1415 9292
8.3636 36364
8.3636 36364
8.3636 36364
At transformer 1-11KV side, Overcurrent relay have pick up of 1.1818A, and your TCC of this relay is Standard inverse
0. 14 ∗ TMS t =
I 0. 02 − 1
Your TMS is 0.14sec, When actual current > 1.1818, then tripping time reduces
pg. 156