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10 COMMISSIONING
d) RESET TIME
A simple verification of which reset mode, selected with the following setpoint:
SETPOINTS/S4 ELEMENTS/NEG SEQ OC/W1 NEG SEQ TIME OC/W1 NEG SEQ TIME OC RESET
can be obtained using the simple test setup in Figure 10–9: GENERAL TEST SETUP on page 10–21. The pro-
cedure consists of repetitive operating time measurements in quick succession. If the reset is selected for
Instantaneous , the operating time is always equal to the nominal time derived from the selected curve. If the
reset is selected as Linear , the operating time varies as a function of the time between successive applications
of the current signal. If this test is performed at current multiples of 2 to 3 times the pickup level, the variations
in operating time are easier to detect.
e) WINDINGS 2 AND 3 ELEMENTS
Because the Negative Sequence Time Overcurrent elements on Windings 2 and/or 3 can be set with com-
pletely different parameters than those for the first element, it is necessary to repeat the full set of tests
described in this section for each winding.
To test these elements, disable all protection elements except for W2 Negative Sequence Time Overcurrent.
Connect the current signal to X = H4 and Y = G4. Repeat all the tests described for the Winding #1 element in
this section. For Winding 3, connect the current signal to X = H7 and Y = G7.
The blocking from logic input, if enabled, can be tested as described in earlier tests for other
elements.
NOTE
This procedure verifies that the Negative Sequence Instantaneous Overcurrent performance matches the in-
service settings. Settings for these elements are found under:
SETPOINTS/S4 ELEMENTS/NEG SEQ OC/W1 NEG SEQ INST OC/...
If the relay settings require testing at current multiples of several times the rated CT secondary value, do not
leave the current signal on for more than a few seconds.
a) WINDING 1 ELEMENT
To ensure that only the Negative Sequence Instantaneous Overcurrent element operates the trip relays (and
any other output relays selected by the logic), disable all protection features except Negative Sequence Instan-
taneous Overcurrent. Use the general test setup in Figure 10–9: GENERAL TEST SETUP on page 10–21.
Connect the current supply to terminals X = H1 and Y = G1 to test the Winding 1 element. Monitor the appro-
priate output relays as per the relay FlexLogic settings.
b) PICKUP LEVEL
1. With the interval timer disabled, apply the current signal and increase its magnitude until the trip relay and
all selected auxiliary relays operate. Compare the measured operating level against the relay settings in:
SETPOINTS/S4 ELEMENTS/NEG SEQ OC/W1 NEG SEQ INST OC/W1 NEG SEQ INST OC PICKUP
With current applied to a single phase, the negative sequence current component is calculated
from:
NOTE
I
=
neg seq
Hence, the phase current will be three times the pickup setting.
GE Power Management
10.6.15 NEGATIVE SEQUENCE INSTANTANEOUS OVERCURRENT
1
×
I
-- -
phase
3
745 Transformer Management Relay
10.6 PROTECTION SCHEMES
10
10-33
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