Negative Sequence Instantaneous Overcurrent - GE TRANSFORMER MANAGEMENT RELAY 745 Instruction Manual

8.5 PROTECTION SCHEMES
OPERATING TIME:
Using a table like the one shown below, select 3 or 4 values of current multiples at which the timing is to be measured.
Enter the expected operating times from the timing curve applied in the settings. Using the setup in Figure 8–9: General
Test Setup on page 8–18 with the Interval Timer enabled, set the current level to the desired value (taking into account the
relationship mentioned above) and apply suddenly by closing the double-pole switch. Record the operate time and com-
pare to the expected value. Repeat for all desired values of current.
CURRENT NOMINAL TIME
MULTIPLE
1.5
3
5
RESET TIME:
A simple verification of which reset mode, selected with the
NEG SEQ TIME OC RESET
18. The procedure 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 sig-
nal. 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.
WINDING 2 AND 3 ELEMENTS:
Because the Negative Sequence TOC elements on Windings 2 and/or 3 can be set with completely 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 Winding 2 Negative Sequence Time Overcurrent. Con-
nect 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 set-
tings. These elements are found under the
If the relay settings require testing at current multiples of several times the rated CT secondary value, do not leave the cur-
rent signal on for more than a few seconds.
WINDING 1 ELEMENT:
8
To ensure that only the Negative Sequence Instantaneous Overcurrent element operates the trip relays (and any other out-
put relays selected by the logic), disable all protection features except Negative Sequence Instantaneous Overcurrent. Use
the general test setup in Figure 8–9: General Test Setup on page 8–18.
Connect the current supply to terminals X = H1 and Y = G1 to test the Winding 1 element. Monitor the appropriate output
relays as per the relay FlexLogic™ settings.
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
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
8-28
Courtesy of NationalSwitchgear.com
MEASURED
TIME
setpoint, can be obtained using the simple test setup in Figure 8–9: General Test Setup on page 8–

8.5.12 NEGATIVE SEQUENCE INSTANTANEOUS OVERCURRENT

S4 ELEMENTS
relay settings.
I
neg seq
745 Transformer Management Relay
S4 ELEMENTS NEG SEQ OC
NEG SEQ OC W1 NEG SEQ INST OC
S4 ELEMENTS
1
×
-- -
I
=
phase
3
8 COMMISSIONING
W1 NEG SEQ TIME OC W1
settings menu.
NEG SEQ OC W1 NEG
(EQ 8.15)
GE Multilin