GE TRANSFORMER MANAGEMENT RELAY 745 Instruction Manual page 264

8.5 PROTECTION SCHEMES
Using a current supply as shown in the figure below, connect the I
1 phase current element and I
output relays as per the relay FlexLogic™ settings.
PICKUP LEVEL:
1. With the interval timer disabled, apply the current signal feeding the phase current element and increase its magnitude
slowly until the trip relay, and all the selected auxiliary relays, operate. The operate level should correspond to the
ELEMENTS RESTRICTED GROUND
2. When the element operates, check that the Trip, Ground, and Pickup LEDs are on and that one of the following mes-
sages is displayed:
LATCHED
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
Otherwise, only the Trip LED should remain on.
4. Reset indicators and clear messages.
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 cur-
rent 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.
SLOPE:
8
1. To measure the slope, connect current signals to the relay as shown in the figure above.
2. Inject the I current such that the ground differential pickup value divided by the I
1
Set I = 0 A. The element will operate as since the current appears as ground differential.
2
3. The slope is calculated from the values of I
where I represents the maximum phase current for the winding being measured.
max
4. As I is increased, the element will reset when the percentage of slope drops below the slope setting. Slowly increase
2
I until the element operates again. Calculate the slope at this point.
2
5. Decrease the slope setting to 0% then continue to increase the I
until the element operates again.
8-26
Courtesy of NationalSwitchgear.com
to terminals G10 and H10 as shown for the ground current element. Monitor the appropriate
2
Figure 8–11: RESTRICTED GROUND TEST SETUP
W1 RESTD GND FAULT
OPERATED
W1 Restd Gnd Fault
ground differential
I
ground differential
%slope ------------------------------------------- -
=
I
max
745 Transformer Management Relay
current source to terminals H1 and G1 for the Winding
1
W1 RESTD GND FAULT PICKUP
W1 RESTD GND FAULT TARGET
current is less than the slope setting.
1
and I as shown below:
max
×
100%
current until the element resets. Slowly increase I
2
8 COMMISSIONING
S4
setting.
was selected as "Latched".
(EQ 8.13)
2
GE Multilin