Protection Schemes
745
Transformer Management Relay
Commission
ing
http://www.GEindustrial.com/multilin
7–30
GE Multilin
To test these elements, disable all protection elements except for Winding 2
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.
Negative Sequence
Instantaneous
Overcurrent
a) Description
This procedure verifies that the Negative Sequence Instantaneous Overcurrent
performance matches the in-service settings. These elements are found under the
S4 ELEMENTS
!"
NEG SEQ OC
!"
W1 NEG SEQ INST OC
settings menu. 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.
b) 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 Instantaneous Overcurrent. Use
the general test setup in FIGURE 7–9: General Test Setup on page 7–18.
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.
c) Pickup Level
1. With the interval timer disabled, apply the current signal and increase its mag-
nitude until the trip relay and all selected auxiliary relays operate. Compare the
measured operating level against the
S4 ELEMENTS
!"
NEG SEQ OC
!"
W1 NEG
SEQ INST OC
!"
W1 NEG SEQ INST OC PICKUP
relay settings.
With current applied to a single phase, the negative sequence current
component is calculated from:
(EQ 7.17)
Hence, the phase current will be three times the pickup setting.
2. When the element operates, check that the Trip and Pickup LEDs are on and one
of the following is displayed:
LATCHED a: W1 Neg Seq Inst OC
or
OPERATED a: 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 LEDs should
remain on if the
W1 NEG SEQ INST OC TARGET
was selected as “Latched”.
Otherwise, only the Trip LED should remain on.
4. Reset indicators and clear messages.
d) Operating Time
Using the setup in
General Test Setup
on page 7–18 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
S4 ELEMENTS
!"
NEG SEQ OC
!"
W1 NEG SEQ INST OC
!"
W1 NEG SEQ
INST OC DELAY
setting.
NOTE
NOTE
I
neg
seq
1
3
---
I
phase
×
=
Summary of Contents for Multilin 745
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