Trouble-Shooting; On-Load Tap-Changer; Pressure Relay - ABB UZE Repair Manual

2 Trouble-shooting

2. Trouble-shooting
This chapter mainly contains infomation used to locate a fault. Instructions for correcting the
fault, replacement of parts etc. are contained in chapter 3, Repairs and Adjustments.

2.1 On-load tap-changer

Error condition
High oil level alarm.
Low oil level alarm.

2.2 Pressure relay

To take the transformer into service after a pressure relay trip without opening the front cover
and carrying out a careful investigation of the active part, and repairing faults, if any, may
cause severe damage to the on-load tap-changer and the transformer.
Error condition
12
The pressure relay has
tripped during normal op-
eration.
Fault finding procedure
A rising oil level in the on-load tap-changer oil conserva-
tor may indicate a leakage between the on-load tap-
changer and the transformer main tank.
Make sure that the cause for the alarm is not over-filling
at commissioning or overhaul. This can be checked by
adjusting the oil level according to "Correct Oil Level"
in the Installation and Commissioning Guide and then
rechecking some time later.
A lowering oil level in the on-load tap-changer may indi-
cate a leakage. If there is no visible leakage, adjust the
oil level according to "Correct Oil Level" in the Installation
and Commissioning Guide then rechecking some time
later.
CAUTION
Fault finding procedure
Tools required:
-
Air pump
-
Manometer
-
Screwdriver
-
Megger (500–2 000 V)
1ZSE 5492-128 en, Rev. 4