Fig. 12
9.4 Surge Arresters
The function of a surge arrester is to intercept and divert
to ground various over voltage transients (such as lightning
surges) which occur on the distribution system. Surge
arresters can be installed in the Air Terminal Chambers
The arresters must be disconnected whenever high potential
or induced potential tests are made on transformers with
arresters.
9.5 Pressure Relief Device
The standard pressure relief device, located on the tank
above the liquid level, relieves excessive internal tank
pressure and reseals at a lower positive pressure. The
pressure relief device is manually operated by grasping
the end-cap (or ring if provided) and slowly pulling the cap
away from the tank until pressure is relieved.
Pressure relief diaphragm (when provided) is located on
tank top hand hole cover.
9.6 Thermometer
When supplied, a thermometer indicates the liquid
temperature near the top of the tank. The temperature
sensitive element is mounted in a leakproof well, permitting
removal of the thermometer without lowering the liquid
level. The device is furnished with an additional pointer, red
in color, to show the highest temperature attained since
last reset.
9.7 Liquid Level Gauge
When supplied, a liquid level gauge is located in the right
side of the front panel or segment 1 to indicate the variation
from the 25 degree C liquid level.
9.8 Pressure-Vacuum Gauge
When supplied, a pressure-vacuum gauge is located in
the right side of the front panel or segment 1. This gauge
indicates whether the gas space in the tank is under positive
or negative pressure.
9.9 Nameplate
A nameplate is supplied on each transformer according
to ANSI standard C57.12.00-1980, Section 5.12. Refer
to the nameplate for transformer ratings and for proper
connections of the transformer to the system. No internal
connections should be made inside the transformer other
than those shown on the nameplate.
9.10 Control Cabinet
WARNING:
THE CONTROL CABINET CONTAINS
CONTROL VOLTAGE AND ELECTRICAL POWER
FOR COOLING FAN OPERATION. ENSURE THAT
CABINET IS ADEQUATELY GROUNDED AND
ALWAYS REMOVE THE CONTROL CABINET
POWER SUPPLY PRIOR TO PERFORMING WORK
INSIDE THE CONTROL CABINET EQUIPMENT OR
CONNECTED ACCESSORIES. FAILURE TO DO SO
COULD RESULT IN SEVERE PERSONAL INJURY,
DEATH OR PROPERTY DAMAGE.
Refer to wiring diagram for electrical circuits inside the
control cabinet. Use an indicating light type device when
checking an alarm switch. Failure to do so could result in
damage. Inspect cords or conduits for wear and evidence
of damage. Repair or replace any damaged cords or
conduits.
The cooling fan motor electrical data can be found on
the motor nameplate or the wiring diagram. The controls
for the fan motor are contained in the control cabinet
mounted on the transformer.
The “Manual-Auto” switch determines the mode of
operation. When the switch is in the “Manual” position, the
fans will operate continuously. When the switch is in the
“Auto” position, the fans will be automatically controlled by
the thermal devices mounted on the transformer.
When specified the “Manual-Off-Auto” type fans switch is
provided. When the switch is in the “Manual” position, the
fans will operate continuously. When the switch is in the
“Off” position, the fans will not operate. When the switch
is in the “Auto” position, the fans will be automatically
controlled by the thermal devices mounted on the
transformer.
The fan motors are normally provided with thermal
overload protection. However, if the fans are designed for
hazardous locations, protection may be provided in the
control cabinet. Refer to the wiring diagram for specifics.
The fan motors have permanently sealed ball bearings
and require no additional lubrication. When assembled,
fan motors are provided with drain plugs installed for
proper orientation. Visually inspect plug placement to
ensure that plugs are correct per fan manufacturer’s
recommendations.
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