GE 850 User Manual

6–76 850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CURRENT ELEMENTS CHAPTER 6: PROTECTION SETPOINTS
Undercurrent (37)
The 850 relay provides three Undercurrent elements per protection group. The
Undercurrent element responds to a per-phase current. An alarm will occur if the
magnitude of any phase current falls below the undercurrent alarm pickup level for the
time specified by the undercurrent alarm delay. Furthermore, a trip will occur if the
magnitude of any phase current falls below the undercurrent trip pickup level for the time
specified by the undercurrent trip delay. The alarm and trip pickup levels should be set
lower than the lowest feeder loading during normal operations.
Undercurrent requires a breaker ‘close’ status to activate the element. In addition, the
Undercurrent element can be blocked upon the closing of the feeder breaker for a period
of time defined by the setting Start Block Delay. This block may be used in applications
when the load requires time to build up to a certain operating level before the undercurrent
element trips or alarms.
FAST PATH:
Breaker has to be configured as Breaker 1 (programmed under Setpoints > System >
Breaker 1) to monitor the breaker close status.
Path: Setpoints > Protection > Group 1 > Current > Undercurrent 1(X)
TRIP FUNCTION
Range: Disabled, Trip, Configurable
Default: Disabled
This setting enables the Undercurrent Trip functionality.
SIGNAL INPUT
Range: dependant upon the order code
Default: CT Bank 1-J1
This setting provides the CT Bank input for the Undercurrent element.
START BLOCK DELAY
Range: 0.00 to 600.00 s in steps of 0.01 s
Default: 0.50 s
The Undercurrent element remains blocked when the breaker closes for a period of time
defined by this setting. The START BLOCK DELAY setting allows the connected load to
build-up to a certain level before the undercurrent element trips or alarms.
TRIP PICKUP
Range: 0.05 to 0.95 x CT in steps of 0.01 x CT
Default: 0.60 x CT
This setting specifies a pickup threshold for the trip function.
TRIP PICKUP DELAY
Range: 0.00 to 180.00 s in steps of 0.01 s
Default: 1.00 s
This setting specifies a time delay for the trip function.
TRIP DROPOUT DELAY
Range: 0.00 to 180.00 s in steps of 0.01 s
Default: 1.00 s
This setting specifies a specifies a time delay to reset the trip command. This delay
should be set long enough to allow the breaker or contactor to disconnect the feeder.
TRIP OUTPUT RELAY X
For details see Common Setpoints
.

GE 850 Specifications

General

Brand	GE
Model	850
Category	Protection Device
Language	English