Electrical Tests On Transformer; After Energizing; Resistance Measurement - ABB UZE Installation And Commissioning Manual

7 Electrical connection and testing

7.3 Electrical tests on transformer

Acceptance tests on the transformer or commissioning can now be performed.

7.4 After energizing

Before any work is carried out on the on-load tap-changer:
Make sure that the transformer is disconnected and that earthing is properly carried
out. Obtain a signed certificate from the engineer in charge.
The cork-rubber gaskets should be retightened after the transformer has been in service for
about two weeks, after all the gaskets have settled at service temperature.
The tightening torque for the gasket between the on-load tap-changer and the transformer
is approximately 90 Nm.
The tightening torque for the front conver, and the connection cover at UZF, should be
42 Nm. The welded stud bolts should not be overtightened.

7.5 Resistance measurement

If there are any problems with to high resistance during measurement of the transformer, the
tap-changer should be operated 10 cycles over all positions to clean the contacts.
Another cause for problems at resistance measurement may be too low measuring current.
We recommend a measuring current of at least 50 A.
26
WARNING
1ZSE 5492-115 en, Rev. 5