Section VI. MAINTENANCE OF TRANSFORMER

Section VI. MAINTENANCE OF TRANSFORMER

transformer nameplate. A table on the transformer

3-12. General

nameplate gives the voltages and current rating for each

Instructions contained in this section are for operator's

tap position.

information and guidance in maintenance of the

transformer.

WARNING

The tap-changer must not be operated while

Solid insulation surrounding an energized

the transformer is energized. Serious

conductor and power apparatus must never

personal injury and / or damage to the

be replied upon to provide protection to

transformer may result.

personnel.

e. To change taps remove the tap changer cap (1,

a. The external surfaces should be inspected at

fig. 3-7) by removing the two hex head bolts (4). With

regular intervals. If they show weathering is taking

the cap removed, the tap position can be observed

place the surfaces should be cleaned and repainted.

through a slot in the indicator cams (3). Use a wrench to

turn the hex head drive mechanism (2).

The

b. Check the pressure gage to make sure the

mechanism must be rotated through 5 / 6 of a turn to

transformer seal is being maintained. The gage reading

make a change of one tap.

Although the drive

should vary as the transformer temperature changes

mechanism can be turned continuously in either

and should normally indicate a positive pressure. A lack

direction placing the wedge in any one of six different

of any change in readings with changes in temperature

positions, only five positions are numbered for use as

is an indication of a leak in the transformer seal and

shown on the transformer nameplate. The unnumbered

should be investigated. Check and make sure vent

position should not be used. After the desired change

valve and sample valve are fully closed.

has been made, make sure that the cap gasket is in

good condition and replace the cap.

c. The meters and gages should be inspected to

gee that all are in good condition, registering properly

NOTE

and have no broken or cracked glass, scarred, or

The slots in the two indicator cams must

damaged cases and are tightly mounted.

coincide before the cap can be seated

d. The wedge-type tap changer provides a means

properly. This is to insure that the cap is

of c(hanging the voltage ratio of a de-energized

not replaced until the tap changer is on

transformer without breaking the transformer seal. It is

position.

It also serves to align an

shipped in place and is set on the position

appropriate position number on the cap with

corresponding to the rated voltage shown on the

the arrow on the mounting flange. Secure

the cap with its two hex head bolts.

3-11