7–54 745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
PROTECTION SCHEMES CHAPTER 7: COMMISSIONING
7.5.19 Insulation Aging
7.5.19.1 Description
The three elements under the insulation aging feature, hottest-spot limit, aging factor limit,
and loss of life limit, must be tested with a valid set of transformer data programmed into
the relay. The ambient temperature must also be programmed (obtained from an RTD or
programmed as 12-month averages). The tests consist of simulating transformer loading
by applying a current signal to winding 1 phase A at the correct frequency.
7.5.19.2 Hottest-spot Limit
The hottest-spot temperature value is a function of load, ambient temperature, and
transformer rating.
Apply a current to winding 1 phase A to represent at least a 100% load
on the transformer.
Use the A2 METERING
LOSS OF LIFE HOTTEST-SPOT
WINDING TEMPERATURE actual value to observe the hottest spot
temperature increases gradually. The simulated load to may be increased
for a faster temperature rise.
When the hottest spot temperature reaches the
S4 ELEMENTS INSULATION AGING
HOTTEST-SPOT LIMIT
HOTTEST-SPOT LIMIT PICKUP operating level, the element should
operate.
Verify all programmed relay operations as per FlexLogic™ settings.
Verify that all the targets and messages are as expected and
programmed.
The time delay can be verified with a watch as the delay is normally set in minutes.
7.5.19.3 Aging Factor Limit
The Aging Factor value is also a function of load, ambient temperature, and transformer
ratings.
Apply a current to Winding 1 Phase A to represent at least a 100%
transformer load.
Use the A2 METERING
LOSS OF LIFE INSULATION AGING
FACTOR actual value to observe that the aging factor increases
gradually.
You may want to increase the simulated load or the simulated or
programmed ambient temperature to cause a faster increase.
When the aging factor reaches the
S4 ELEMENTS INSULATION AGING AGING
FACTOR LIMIT
AGING FACTOR LIMIT PICKUP operating level, the element should
operate.
Verify all programmed relay operations as per FlexLogic™ settings.
Verify that all the targets and messages are as expected and
programmed.
The time delay can be verified with a watch as the delay is normally set in minutes.
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