GE 745 Instruction Manual page 292

PROTECTION SCHEMES
7.5.19 Insulation Aging
7.5.19.1 Description
7.5.19.2 Hottest-spot Limit
7.5.19.3 Aging Factor Limit
7–54
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.
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
WINDING TEMPERATURE
temperature increases gradually. The simulated load to may be increased
for a faster temperature rise.
When the hottest spot temperature reaches the
HOTTEST-SPOT LIMIT HOTTEST-SPOT LIMIT PICKUP

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.
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
FACTOR
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
FACTOR LIMIT AGING FACTOR LIMIT PICKUP

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.
A2 METERING LOSS OF LIFE

actual value to observe the hottest spot
S4 ELEMENTS
operating level, the element should
A2 METERING LOSS OF LIFE

actual value to observe that the aging factor increases
S4 ELEMENTS INSULATION AGING

operating level, the element should
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 7: COMMISSIONING
HOTTEST-SPOT

INSULATION AGING

INSULATION AGING

AGING

