ABB UC Manual del usuario - Página 6

Navegue en línea o descargue pdf Manual del usuario para Equipamiento industrial ABB UC. ABB UC 12 páginas. On-load tap-changers

Maintenance schedule

Maintenance of the on-load tap-changer consists of three major steps:

Inspection to be carried out by site personnel once a year (see below)

Overhaul to be carried out by a specialist at intervals stated on the rating plate

Contact replacement to be carried out by a specialist. The need for contact replacement is decided

during maintenance.

To maintain the high reliability of the on-load tap-changer it is important that the inspections and

the overhauls be carried out at the interval stated on the rating plate.

A specialist is a service engineer from ABB or an authorized person trained by ABB for maintenance

work on UC on-load tap-changers.

NOTE: If the number of operations is small and the on-load tap-changer is filled with degassed oil

after commissioning or overhaul the oil level should be checked one month after filling, see section 2

under "Procedure". The absence of a gas cushion means a risk for a false trip of the pressure relay.

Inspection

On the rating plate, "inspection once a year" is recommended. This principally concerns the motor-

drive mechanism and refers to a visual inspection inside the BUE/BUL cabinet to check that nothing is

loose, and that the heater is functioning.

In the motor-drive mechanism a counter registers every tap-change operation. During inspection the

counter is read. If possible, motor and counter are to be tested by operating one step and then back.

If the on-load tap-changer has its own oil conservator, the breather and the oil level indicator on the oil

conservator are to be checked according to the instructions from the transformer manufacturer.

The inspection is to be carried out while the transformer is in service.

Approval should be given for inspection as well as for operating the on-load tap-changer.

On the conservator the following are to be checked:

Oil level

Breather

In the motor-drive mechanism the following items are to be checked:

Motor and counter

Emergency stop

Heater

Earth fault protector for the outlet (option)

If the on-load tap-changer is equipped with an oil filter unit, the following item is to be checked:

Pressure drop over the filter

Required tools

The following eq uipment is required for the inspection:

Set of screwdrivers

Pen and note pad

CAUTION