GE 745 Instruction Manual page 269

CHAPTER 7: COMMISSIONING
Note
NOTE
7.5.8 Neutral Instantaneous Overcurrent 1
7.5.8.1 Description
7.5.8.2 Winding 1 Element
7.5.8.3 Pickup level
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
 Connect the current signal to X = H4 and Y = G4 and repeat tests in this
section.
 To test winding 3 elements, disable all protection elements except for
W3 NEUTRAL TIME OVERCURRENT
 Connect the current signal to X = H7 and Y = G7 and repeat the tests in
this section.
The blocking from logic input, if enabled, can be tested as described in earlier tests for
other elements.
This procedure verifies that the neutral instantaneous overcurrent performance is as per
the in-service settings. Settings for these elements are found under the
NEUTRAL OC W1 NTRL INST OC 1

current multiples of several times the rated CT secondary value, do not leave the current
signal on for more than a few seconds.
To ensure that only the neutral instantaneous overcurrent 1 element operates the trip
relays (and any other output relays) selected by the logic,
 Disable all protection features except neutral instantaneous overcurrent
1. Use the general test setup shown in FIGURE 7–9: General test setup
on page 7–25.
 Connect the current supply to terminals X = H1 and Y = G1 to test the
winding 1 phase A element.
 Monitor the appropriate output relays as per the relay FlexLogic™
settings or assigned relay settings.
 With the interval timer disabled, apply the current signal and increase its
magnitude until the trip relays (and all the selected auxiliary relays)
operate.
 Compare the measured operating level against the
NEUTRAL OC
PICKUP
 Check that, when the element operates, the Trip and Pickup LEDs are on
and one of the following messages is displayed:
LATCHED a: W1 Ntrl Inst OC 1 or OPERATED a: W1 Ntrl Inst OC
1
.
setpoints menu. If the relay settings require testing at
W1 NTRL INST OC 1

value.
PROTECTION SCHEMES
S4 ELEMENTS
S4 ELEMENTS

W1 NEUTRAL INST OC 1


7–31