Westinghouse PS-1002, Инструкция, Страница: 12 / 36

10
Fig.
6 Front View of TR0-2 Relay
ticipated rises in ambient. In that region of the dial above
80%, a change of 1 °C in ambient temperature is virtually
equivalent to a 1% change in thermal load.
Should a check on accuracy and calibration be indi­
cated, consult with the factory or obtain Instruction
Leaflet 48-062-1 7.
5.10 Sudden Pressure Relay
Transformers may be furnished with a sudden pressure
relay as an optional item. The sudden pressure relay is
mounted on the case cover with its main pressure sensing
element in direct contact with the gas cushion of liquid­
filled transformers. Positive operation of the bellows­
actuated micro-switch occurs only in the event of an ab­
normal rate of rise of internal pressure and energizes a
multi-contact seal-in relay fed from a separate voltage
source. The relay's sensitivity is essentially unaffected
by the existing static pressure in the gas space, making it
sensitive to the high rates of rise that are associate d with
arc-producing faults in the transformer winding itself.
CAUTION
The sudden pressure relay must be correctly installed on
its mounting boss. The bellows and equilizer holes must
be above the opening in the boss. If the relay is installed
180° from the correct position, the relay may fail when
vacuum is pulled on the transformer.
A seal-in relay reset switch, and the associated circuitry
are mounted in a separate control cabinet. The seal-in re­
lay is energized when the sudden pressure micro-switch
operates and remains so until manually reset with the re­
set switch. Seal-in relay loads should be limited to the
values given in the table listing given on the wiring dia­
gram. The Voltrap must be disconnected if trip circuit
voltage is higher than 270 volts.
If field tests are required to check out the relay, con­
sult the factory or obtain Instruction Leaflet 48-065-1.
After a Sudden Pressure Relay has tripped the p rimary
circuit breaker and disconnected the transformer, it be­
comes necessary to decide whether to reclose the breaker
and put the transformer back in service. If the transformer
is severely damaged, it would probably trip again imme­
diately but not before suffering additional damage. If the
transformer is not badly damaged, it might carry load for
some time. The transformer might not even be damaged at
all. The decision must be made by the user, but the fol­
lowing steps are suggested to help determine the extent of
damage:
l . Use a portable Combustible Gas Detector to check for
combustible gas products of decomposition in the gas
space. Refer to the operating instructions for the Gas De­
tector.
MOUNTING BOSS
\ PART OF TANK )
EQUALIZER
PLUG
PRESSURE TIGHT CONNECTOR
Fig. 7
Sudden Pressure Relay