7–38 745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
PROTECTION SCHEMES CHAPTER 7: COMMISSIONING
FIGURE 7–11: Restricted ground test setup
7.5.14.3 Pickup Level
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
S4 ELEMENTS
RESTRICTED GROUND W1 RESTD GND FAULT W1 RESTD GND
FAULT PICKUP
setting.
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
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.
Reset indicators and clear messages.
7.5.14.4 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.
7.5.14.5 Slope
To measure the slope, connect current signals to the relay as shown in
the figure above.
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