Remote/local Tap Operation

The on-load tap changing equipment shall have the provision for mechanical and electrical control from a local position. For local mechanical operation, the operating handle shall be brought outside the tank for operation from floor level with provision to lock the handle in each tap position.

In driving mechanism cubicle

-        “RAISE-LOWER” control switch

-        Means for manual operation when power supply is lost

-        Tap change operation counter

The OLTC should be designed to be controlled from the remote. The remote OLTC panel with the switching and control devices shall be provided in the switchgear room.

   Insulating Oil

The insulating oil shall conform to the latest revision of IS 335/IEC publication 296, properly inhibited for preventing of sludging.

The necessary first filling of oil shall be supplied for the transformer in non-returnable container suitable for outdoor storing. Ten percent (10%) excess oil shall also be provided to take wastage into account.

    Oil Preservation System

Oil preservation shall be by a means of conservator tank or by a sealed tank system.
                       Conservator Tank System

1)      The conservator tank shall be mounted on a bracket fixed on the tank.

2)      The conservator tank shall be provided with two compartments, on for the main transformer tank while the other for the OLTC compartment. The partition barrier shall be provided so that OLTC oil shall not be mixed up with the transformers oil under any circumstances.

3)      One compartment shall be connected with the main transformer tank by pipes through double float Buchholz Relay (gas operated relay) with valves at both ends.

4)      The other compartment shall be connected with the OLTC compartment by pipes through single float Buchholz Relay/Oil Surge Relay with valves at both ends.

5)      Contact of the oil in the compartment for the main tank with atmosphere shall be prohibited by using a flexible urethane air cell. The cell shall be vented in to the atmosphere through a silica gel breather and shall inflate or deflate as oil volume changes.

6)      Both compartments shall be provided with their own breather, filler cap and drain plug.

7)      Each compartment of the conservator shall be provided with a dial type level indicator visible from the ground level and fitted with a low oil level alarm contact. Plain oil level gauge shall also be provided to each compartment.

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