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10 COMMISSIONING
To check the threshold without performing computations, inject balanced 3-phase currents into any
winding. With balanced conditions, there is no effect on magnitude due to phase shifting and zero-
sequence removal has no effect. However, the CT ratio mismatch is still applicable.
NOTE
10. Repeat the minimum pickup level measurements for the B-phase (inputs H2 and G2) and the C-phase ele-
ment (inputs H3 and G3).
The above tests have effectively verified the minimum operating level of the three harmonic restrained differen-
tial elements. If desired the above measurements may be repeated for the phase inputs for the other wind-
ing(s). The results should be identical.
b) VERIFICATION OF LOCAL RESET MODE
1. Set the differential element with a latched target. Apply enough current to cause the relay to operate, then
remove the current. The trip LED and the phase LED should be latched on.
2. Set Local Reset Block to Disabled as follows:
SETPOINTS/S1 745 SETUP / RESETTING / LOCAL RESET BLOCK: Disabled
3. Press the RESET key. The target should reset.
4. Set Local Reset Block to Logic Input 1 (2-16) as follows:
SETPOINTS/S1 745 SETUP / RESETTING / LOCAL RESET BLOCK: Logc Inpt 1 (2-16)
5. Press the RESET key and verify that the target does not reset if the logic input is not asserted. Verify the
status of selected logic input through the actual value:
ACTUAL VALUES/A1 STATUS / LOGIC INPUTS / LOGIC INPUT 1 (2-16)
6. Assert the selected logic input, apply the current to cause the target to latch and verify that pressing the
RESET button does not reset the LED. The following message should appear:
SS INAVLID KEY: MUST
SS BE IN LOCAL MODE
c) VERIFICATION OF REMOTE RESET MODE
1. Set the differential element with a latched target. Apply enough current to cause the relay to operate, then
remove the current. The trip LED and the phase LED should be latched on.
2. Set Remote Reset Signal to Logic Input 1 (2-16) under:
SETPOINTS/S1 745 SETUP / RESETTING / REMOTE RESET SIGNAL: Logc Inpt 1 (2-16)
3. Assert Logic Input 1. The target should reset.
d) VERIFICATION OF SOLID STATE OUTPUT
1. If the solid state output is used to drive auxiliary relays, verify that these relays operate whenever the relay
is in a trip condition. Ensure that the current though the auxiliary coils is interrupted by an external contac-
tor between each test.
2. To avoid operating the breaker during the commissioning process when the solid state output operates the
breaker directly, use the circuit shown in Figure 10–4: SOLID STATE OUTPUT TEST CIRCUIT to verify
this output. Whenever the relay is in a trip state, current flows through the load resistor. Select the resistor
for approximately 1 × CT of DC current with the normal DC supply voltage used in your relay scheme.
GE Power Management
745 Transformer Management Relay
10.6 PROTECTION SCHEMES
10
10-15
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