GE 845, Instruction Manual

Page: 279 / 552

CHAPTER 4: SETPOINTS PROTECTION
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 4–151
Transformer Overload
The Transformer overload element may be used as an instantaneous element with no
intentional delay or as a definite time element. Each winding load current is compared
with the pickup setpoint to produce an alarm or trip condition. Alternatively, the overload
detection is available through the Over-temperature alarm input. An external transformer
over temperature detector can be connected to this input.
Setpoints
Path:
Setpoints > Protection > Group 1(6) > Transformer > Overload
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
PICKUP
Range: 50 to 300 % in steps of 1 %
Default: 208 %
This setting identifies the level of transformer overload, where the pickup delay starts
timing. For a two winding transformer, the setting is expressed as a percentage of the
transformer base MVA rating, and is normally set at or above the maximum rated MVA
from the transformer nameplate. For a three winding transformer, the setting is
expressed as a percentage of the winding base MVA rating.
PICKUP DELAY
Range: 0 to 60000 seconds in steps of 1 s
Default: 10 seconds
OVERTEMP INPUT
Range: Off, Any FlexLogic operand
Default: Off
Select Any FlexLogic operand that, when asserted, indicates the transformer cooling
system has failed or an over-temperature condition exists on the transformer.
BLOCK
Range: Off, Any FlexLogic operand
Default: Off
OUTPUT RELAYS
Range: Do Not Operate, Operate
Default: Do Not Operate
EVENTS
Range: Enabled, Disabled
Default: Enabled
TARGETS
Range: Self-reset, Latched, Disabled
Default: Latched