C Operating Time - GE 745 TRANSFORMER MANAGEMENT RELAY Instruction Manual

10.6 PROTECTION SCHEMES
2. When the element operates, check that the TRIP and PICKUP LEDs are on and the following is displayed:
SS LATCHED (OPERATED):
SS W1 Neg Seq Inst OC
3. Reduce the current until the element resets. The reset level should be 97% of the operate level. When the
element resets, the TRIP and message indicators should remain on if the TARGET was selected as
latched. Otherwise, only the TRIP indicator should remain on.
4. Reset indicators and clear messages.
c) OPERATING TIME
Using the setup in Figure 10–9: GENERAL TEST SETUP on page 10–21 with the Interval Timer enabled, set
the current level to 1.5 times the operate level of the element and apply suddenly by closing the double-pole
switch. Record the operate time and compare to the setting under:
SETPOINTS/S4 ELEMENTS/NEG SEQ OC/W1 NEG SEQ INST OC/W1 NEG SEQ INST OC DELAY
d) WINDING 2 AND 3 ELEMENTS
Because the Winding 2 and 3 elements can be set with completely different parameters than the element for
Winding 1, it is necessary to repeat the full set of tests described for the Winding 1 element in this section.
Connect the current supply to terminals X = H4 and Y = G4 to test the Winding 2 element. Use X = H7 and
Y = G7 for the Winding 3 element.
The blocking from logic input, if enabled, can be tested as described in earlier tests for other
elements.
NOTE
The power system frequency is measured from the voltage input if it has been enabled. If there is no voltage
input, it is measured from the phase A Winding #1 current signal. These tests require a variable-frequency cur-
rent source for relays without a voltage input and a variable-frequency voltage and current source for relays
with a voltage input. Connections are shown in the figure below. Only perform tests specific to the relay model.
The underfrequency, overfrequency, and frequency decay elements are all supervised by optional
adjustable minimum current and minimum voltage level detectors. When testing the performance of
these elements on a 745 with the voltage input enabled, it may be necessary to inject a current signal
NOTE
into Winding 1 phase A if the current supervision is enabled, or else the detectors will not operate.
10
10-34
Figure 10–11: FREQUENCY ELEMENT TESTING
745 Transformer Management Relay
10 COMMISSIONING
10.6.16 FREQUENCY ELEMENTS
GE Power Management