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Protection Schemes
745
Transformer Management Relay
Commission
ing
http://www.GEindustrial.com/multilin
7–27
GE Multilin
Restricted Ground Fault
Element Test
a) Description
This procedure verifies that the Restricted Ground Fault performance matches the
in-service settings. The ground element measures the current signal connected to
the ground current input CT, H10 and G10 or F12 and E12. The neutral (3
I
o
) current
is calculated from the vector sum of the three phase currents. Injecting current into
one phase automatically produces a neutral current (i.e. 3
I
o
=
I
A
). Settings for
these elements are found in the
S4 ELEMENTS
!"
RESTRICTED GROUND
!"
W1(3) RESTD
GND FAULT
setpoints menu.
b) Winding 1 Element
To ensure that only the Restricted Ground Fault element operates the trip relays
(and any other output relays selected by the logic) disable all protection features
except Restricted Ground Fault.
Using a current supply as shown in the figure below, connect the
I
1
current source
to terminals H1 and G1 for the Winding 1 phase current element and
I
2
to terminals
G10 and H10 as shown for the ground current element. Monitor the appropriate
output relays as per the relay FlexLogic™ settings.
FIGURE 7–11: Restricted Ground Test Setup
c) Pickup Level
1. With the interval timer disabled, apply the current signal feeding the phase cur-
rent element and increase its magnitude slowly until the trip relay, and all the
selected auxiliary relays, operate. The operate level should correspond to the
S4
ELEMENTS
!"
RESTRICTED GROUND
!
W1 RESTD GND FAULT
!"
W1 RESTD GND FAULT
PICKUP
setting.
2. When the element operates, check that the Trip, Ground, and Pickup LEDs are
on and that one of the following messages is displayed:
LATCHED a: W1 Restd Gnd Fault
or
OPERATED a: W1 Restd Gnd Fault
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 RESTD GND FAULT TARGET
was selected as “Latched”.
Otherwise, only the Trip LED should remain on.
4. Reset indicators and clear messages.
d) Operating Time
Select three (3) or four (4) delay times at which the timing is to be measured. With
the Interval Timer enabled, set the current level to the desired value and apply
suddenly by closing the double-pole switch. Record the operate time and compare
to the expected value. Repeat for the all the desired values of current.
Содержание Multilin 745
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