GE P742

Troubleshooting
P74x/EN TS/N
a7
MiCOM P74
1, P742, P743
(TS) 12-
5
TS
3. POWER UP ERRORS
If the relay does not appear to power up then the following procedure can be used to
determine whether the fault is in the external wiring, auxiliary fuse, power supply module of
the relay or the relay front panel.
Test Check Action
1
Meas
ure auxiliary voltage on
terminals 1 and 2; verify voltage
level and polarity against rating the
label on front.
Terminal 1 is –dc, 2 is +dc
If auxiliary voltage is present and correct,
then proceed to test 2. Otherwise the
wiring/fuses in auxiliary supp
ly should be
checked.
2
Do LEDs/and LCD backlight
illuminate on power-up, also check
the N/O watchdog contact for
closing.
If they illuminate or the contact closes and no
error code is displayed then error is probably
in the main processor board (front panel). If
they do not illuminate and the contact does
not close then proceed to test 3.
3
Check Field voltage output
(nominally 48V DC)
If field voltage is not present then the fault is
probably in the relay power supply module.
Table 2: Failure of relay to power up