All connectors must be dry and clear of any contamination
before installation. Unused terminals should be properly
terminated to prevent possible contamination. Follow the
manufacturer’s instructions and warnings on the use of
these terminations.
9.1.2 Porcelain Bushings
High or medium voltage porcelain bushings (when
provided) are externally clamped, gasketed bushings with
eyebolt-type or spade-type terminals. Attachment lugs
(when provided) are supplied to mate with applicable cable
sizes.
9.2 Fuses
For Unit Substations, fuses are typically provided
in the adjoining high or medium voltage section or in the
adjoining low voltage section.
9.3 HIGH VOLTAGE SWITCHES
For Unit Substations,
high voltage or medium voltage line switches are typically
provided in the adjoining high or medium voltage section.
9.3.3 Tap Changer
WARNING:
DE-ENERGIZE THE TRANSFORMER
BEFORE OPERATING THE TAP CHANGER.
FAILURE TO DO SO CAN CAUSE SEVERE INJURY,
DEATH OR PROPERTY DAMAGE.
The tap changer provides a means of changing the voltage
ratio of a transformer. The transformers are normally
supplied with an externally operated high voltage tap
changer, located on the front panel of the transformer.
(refer to Fig. 11):
A. De-energize the transformer.
B. Back out the locking screw until it is clear of the locking
hole.
C. Turn the handle to the desired tap position.
D. Tighten the locking screw to minimize the possibility of
unintentional movement.
Some large-size units are furnished with a power-
transformer tap changer drive which requires pulling of a
locking pin and a full turn of the handle for each change in
tap position.
Fig. 11
9.3.4 Dual Voltage Switch
WARNING:
DE-ENERGIZE THE TRANSFORMER
BEFORE OPERATING THE DUAL VOLTAGE SWITCH.
FAILURE TO DO SO CAN CAUSE SEVERE INJURY,
DEATH OR PROPERTY DAMAGE.
WARNING:
WHEN CHANGING VOLTAGE POSITION,
FUSES MAY HAVE TO BE REPLACED WITH THOSE
OF THE PROPER RATINGS.THE USE OF AN
IMPROPERLY RATED FUSE CAN CAUSE SEVERE
INJURY, DEATH OR PROPERTY DAMAGE.
On a dual voltage switch, Position 1 is the low or multiple
connected position while Position 2 is the high or series
connected position. To change the voltage position, proceed
as follows (refer to Figure 12):
A. De-energize the transformer.
B. Back out the locking screw until it is clear of the locking
hole.
C. Pull out on the handle until it will rotate.
D. Rotate the handle to the new position.
E. Release the handle.
F. Tighten the locking screw to minimize the possibility of
unintentional movement.
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