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10 COMMISSIONING
1. Connect the test setup as below to supply the A-phase element. Set the fundamental current level to the
CT rated secondary value. The harmonic restraint differential element of phase A should be operated.
2. Increase the 5th harmonic component to a value well above the 5th harmonic restraint setting shown in:
SETPOINTS/S4 ELEMENTS/DIFFERENTIAL/5th HARM INHIBIT/5th HARMONIC INHIBIT LEVEL
3. Remove the total current signal and reapply. The relay should not operate. Decrease the 5th harmonic
component until the element operates.
4. Calculate the percentage 5th harmonic to restrain from the following equation:
×
100
level of 5th harmonic
%5th
=
---------------------------------------------------------------------- -
level of fundamental
5. Compare this value to the relay setting.
j) ENERGIZATION DETECTION SCHEME
Refer to Section 5.6.4 DIFFERENTIAL on page 5–46 for a description of this feature. This feature is activated
by up to three inputs: breaker auxiliary switch, current below a threshold, or absence of voltage. The procedure
below will test the current-level enabling feature. A similar approach can be used to verify the other two
enabling functions, with the proper test equipment.
1. Enable the Energization Detection Scheme with the following setpoint:
SETPOINTS/S4 ELEMENTS/DIFFERENTIAL/ENERGIZATION INHIBIT/ENERGIZATION INHIBIT FUNCTION: Enabled
2. Make the following setpoint changes:
SETPOINTS/S4 ELEMENTS/DIFFERENTIAL/ENERGIZATION INHIBIT/ENERGIZATION IHIBIT PARMETERS: 2nd
SETPOINTS/S4 ELEMENTS/DIFFERENTIAL/ENERGIZATION INHIBIT/HARMONIC AVERAGING: Disabled
SETPOINTS/S4 ELEMENTS/DIFFERENTIAL/ENERGIZATION INHIBIT/ENERGIZATION INHIBIT LEVEL: 15%
SETPOINTS/S4 ELEMENTS/DIFFERENTIAL/ENERGIZATION INHIBIT/ENERGIZATION INHIBIT DURATION: 5 s
SETPOINTS/S4 ELEMENTS/DIFFERENTIAL/ENERGIZATION INHIBIT/ENERGIZATION SENSING BY CURRENT: Enabled
SETPOINTS/S4 ELEMENTS/DIFFERENTIAL/ENERGIZATION INHIBIT/MINIMUM ENERGIZATION CURRENT: 0.10 × CT
3. Preset current with harmonic content just above the Energization Inhibit Level used during the "energiza-
tion period". Apply the current signal and measure the operating time. The time should be equal to "energi-
zation period" plus approximately 50 ms.
4. Disable the energization detection scheme and repeat the timing test. The operate time should be the nor-
mal operating time of Harmonic Restraint Differential element.
GE Power Management
Figure 10–8: 5TH HARMONIC RESTRAINT TEST
745 Transformer Management Relay
10.6 PROTECTION SCHEMES
10
10-19
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