Overexcitation Inhibit Test; Blank Test Tables; Overexcitation Inhibit Test Procedure; Differential Restraint Tests - GE T35 Instruction Manual

OVEREXCITATION INHIBIT TEST

8.4 Overexcitation inhibit test

8.4.1 Overexcitation inhibit test procedure

The Overexcitation Inhibit Test requires a secondary injection from a source capable of producing an adjustable 5th
harmonic component. Use the appropriate commissioning tables at the end of this chapter to record values.
This procedure is based upon the example provided in the Differential Characteristic Test Example section. The transformer
parameters are as follows:
• Transformer — Y/y0°, 230/69 kV, CT1 (300:1), CT2 (1000:1)
• 5th Harmonic Setting — 10%
1. Connect the relay test set to inject current into the Winding 1 Phase A CT input.
2. Inject a current into the relay until the biased Differential element operates.
3. Confirm that ONLY the differential element has operated.
4. Increase the 5th harmonic content level until the element drops out. Record this value as the Overexcitation Inhibit
Level Pickup.
5. Gradually decrease the harmonic content level until the element picks up. Record this value as the Overexcitation
Inhibit Level Dropout.
6. Switch off the current.
7. Repeat steps 1 through 6 for phases B and C.
8. Repeat steps 1 through 7 for winding 2 (and windings 3 and 4 if necessary).
Table 8-4: Overexcitation inhibit test summary
Phase Injected
W1 Current
1 A ∠0°
A
1 A ∠0°
B 4 A ∠0°
4 A ∠0°
C 2 A ∠0°
2 A ∠0°

8.5 Blank test tables

8

8.5.1 Differential restraint tests

Table 8-5: Differential characteristic test table
Test Phase
Balanced A
Condition
B
C
8-14
W1 5th W2 Current W2 5th
Harmonic Harmonic
0 A ∠0°
8% 0
0 A ∠0°
10% 0
8.5% 2 A ∠–180° 9%
9.5% 2 A ∠–180° 9%
9% 4 A ∠–180° 8.5%
9% 4 A ∠–180° 9.5%
Injected current
W1 Current W2 Current
Displayed
I 5th
d
Harmonic
1 pu 8%
1 pu 10%
2 pu 8%
2 pu 10%
2 pu 8%
2 pu 10%
Displayed current
Differential Restraint
T35 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 8: COMMISSIONING
Status
I
r
1 pu Operate
1 pu Block
4 pu Operate
4 pu Block
4 pu Operate
4 pu Block
Status
Not Applicable