Placing the Relay Into Service
745
Transformer Management Relay
Commission
ing
http://www.GEindustrial.com/multilin
7–40
GE Multilin
Transformer Overload
a) Testing Note
The transformer overload element uses the Phase A current of each winding to
compute a transformer loading. The computation assumes a rated voltage on the
wInding, hence the loading is effectively a percent of rated load current.
b) Operating Level
1. Inject a fundamental-frequency current into Phase A of Winding 1. Increase the
current signal to a value just above the Transformer Overload Pickup setting
(take into account the CT ratio and the rated-MVA phase current to set the cur-
rent correctly). The element should operate after its set time delay.
2. Check that the Trip, Pickup (and Alarm if selected) LEDs are on, and one of the
following is displayed:
LATCHED: Xformer Overload
or
OPERATED: Xformer Overload
3. Lower the current until the element resets. The reset value should be
approximately 97% of the operate value. Verify that the Pickup and Alarm LEDs
reset if the target function is set to “Self-resetting”. The Trip LED should remain
latched.
c) Operating Time
Using the setup in
Frequency Element Testing
on page 7–31 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
!"
XFORMER OVERLOAD
!"
TRANSFORMER OVERLOAD
DELAY
setting.
The blocking from logic input, if enabled, can be tested as described in
earlier tests for other elements.
Placing the Relay Into Service
Precautions
The procedure outlined in this section is explicitly concerned with the 745 relay and
does not include the operation/commissioning or placing into service of any
equipment external to the 745. Users should have already performed such tests as
phasing of CTs, ratio measurement, verification of saturation curve, insulation test,
continuity and resistance measurements.
Procedure
1. Restore all settings and logic to the desired in-service values. Verify against the
check list prepared while testing the relay.
2. Upload all the 745 setpoints to a computer file and print for a final inspection to
confirm that all setpoints are correct.
3. Set the 745 clock (date and time).
4. Clear all historical values stored in the relay by entering “Yes” at
A3 EVENT
RECORDER
!"
EVENT DATA CLEAR
!
CLEAR EVENT RECORDER
.
5. Remove all test connections, supplies, monitoring equipment from the relay
terminals and relay panels except for equipment to be used to monitor first
transformer energization. Restore all panel wiring to normal except for those
changes made intentionally for the first energization (blocking of some tripping
functions for example).
6. Perform a complete visual inspection to confirm that the 745 is ready to be
placed into service. Ensure that the relay is properly inserted in its case.
Energize the relay power supply and verify that the Relay In Service LED is ON,
and that the Self-Test Error LED is OFF, establishing that the relay is operating
normally.
NOTE
Summary of Contents for Multilin 745
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