Westinghouse PS-1002, Инструкция, Страница: 28 / 36

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e) Percent impedance on the same kV A base must be
the same within 7 . 5 % for two winding transformers.
For multiwinding and auto transformers the limit is
10%.
Refer to Instruction Leaflet 48 - 0 6 7 - 1 for further in­
structions.
7 . Transformers are normally designed for operation at
altitudes below 1 0 0 0 meters (3 3 0 0 ft.). To operate a
transformer above 1 0 0 0 meters, it is necessary to reduce
the electrical load and to increase the electrical insula­
tion clearances between energized terminals. Refer to
ANSI C 5 7.1 2 . 0 0 and C 5 7.1 2 . 92 for detailed guidelines.
If the transformer has been designed to allow opera·
tion at altitudes above 1 0 0 0 meters, the nameplate will
state the maximum design altitude.
8. Do not connect a load to a transformer whose tem­
perature is -2 0°C (-4°F) or less. When the temperature
is less than or equal to -2 0°C, the liquid level gauge will
indicate " LO" liquid or less. The transformer should be
energized and allowed to warm up (above -2 0°C) before
connecting electrical load. To do otherwise may result in
electrical failure or overheating the transformer. Electrical
failure can result if energized internal parts are above
liquid. The core and coils can overheat if solidified liquid
blocks the cooling tubes.
9 . Some transformers have internal terminal boards or
switches to select either of two voltages on a winding or
either delta or wye connections on a winding. The trans­
former must always be de-energized to change these con­
nections. Depre ssurize the tank before opening a handhole
to gain access to an internal terminal board .
7.3 Inherent Hazards
Transformers by the nature of their construction and use
can be dangerous.
1 . The voltage present in energized transformers is a dan­
ger to the life of anyone coming in contact with it.
2 . Internal pressure may become excessive causing me­
chanical pressure relief device operation. Anyone near the
transformer may be sprayed with hot flammable insulat­
ing li quid. Anyone attempting to remove a bolted hand­
hole runs the risk of being hit by the cover if the internal
pressure is not vented first.
3 . Oil filled transformers present a fire h azard to the in­
stallation area. All liquid leaks must be repaired imme­
diately because transformer liquid is very flammable.
4. Should an internal arc occur in the unit, the internal
pressure will increase and may increase so rapidly that
the tank may rupture, even though the mechanical pres­
sure relief device has operated.
IN THE EVENT OF TRANSFORMER F AlLURE, CON­
TINUED CONDUCTION OF FAULT CURRENT MAY
RESULT IN THE VIOLENT RUPTURE OF THE TRANS­
FORMER TANK, CAUSING A HAZARD TO LIFE AND
PROPERTY.
8. MAINTENANCE
8 .I After the transformer has been properly installed and
is in operation under the conditions for which it was de­
signed , it must receive periodic tests and inspections.
The following periodic test and inspections are rec­
ommended so that the owner can detect the adverse af­
fects of unusual operation conditions or verify that the
transformer's operation is normal. Refer to Table 3 for
frequency of inspections.
1 . The gauge readings should be recorded as well as the
ambient temperature and the Kva load at that time. Any
abnormal reading as explained in the accessory description
section of this book is justification to make other diagnos­
tic tests or inspections immediately . Readings should be
made on a schedule that is rigidly adhered to.
2. Whenever the transformer is de-energized, inspect
bolted electrical connections to the transformer. A loose
bolted connection is a high resistance connection that will
generate enough heat during operation to melt the elec­
trical conductors causing at the very least an interruption
in service and worse a transformer failure.
3 . The transformer should be inspected for leaks at weld
joints and gasket surfaces. If there is reason to suspect a
gas or liquid leak, make a pressure test according to the
instructions in Section 6 . 6
. 1 .
4 . Check the cooling fans by setting the control switch
to the "manual" or "on" position. The fans should ro­
tate at full speed within 5 seconds. The fans should rotate
with very little vibration. The bearings of fan motor are