GE 745 Instruction Manual page 265

CHAPTER 7: COMMISSIONING
7.5.4.6 Phase B and C Elements
7.5.4.7 Winding 2 and 3 Elements
Note
NOTE
7.5.5 Phase Instantaneous Overcurrent 1
7.5.5.1 Description
7.5.5.2 Winding 1 elements
7.5.5.3 Pickup level
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
If the Phase A element performed correctly and met specifications, repeat the pickup level
portion of the above test for the B and C phases of winding 1. For Phase B, X = H2 and
Y = G2. For phase C, X = H3 and Y = G3. The displayed message should change to indicate
the correct phase, winding, and element that operated.
Because the winding 2 and 3 elements can be set with completely different parameters
than the elements for winding 1, it is necessary to repeat the full set of tests described
above for each winding.
The blocking from logic input, if enabled, can be tested as described in earlier tests for
other elements.
This procedure verifies that the phase instantaneous overcurrent performance matches
the in-service settings. The settings for these elements are found under the
PHASE OVERCURRENT

least five times the rated CT secondary value. Do not leave the current signal on for more
than a few seconds!
To ensure that only the phase instantaneous overcurrent 1 element operates the trip
relays (and any other output relays) selected by the logic, disable all protection features
except phase 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 output relays from Phase IOC settings.
 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
PHASE OC
setpoint.
 Check that Trip, Pickup, and Phase A(C) LEDs turn on when the
element operates.
 Check that one of the following messages is displayed:
LATCHED a: W1 Phase Inst OC 1 or OPERATED a: W1 Phase Inst
OC 1
setpoints menu. The testing occurs at current multiples of at
W1 PHASE INST OC 1

PROTECTION SCHEMES
S4 ELEMENTS
S4 ELEMENTS
W1 PHASE INST OC 1 PICKUP


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