GE MI-869

869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL A–1
869 Motor Protection System
Appendix A
GE
Grid Solutions
Appendix A
Application Notes
Contactor Current Supervision
In some cases, the fault current can exceed the current which the contactor is rated to
interrupt. If such a condition has been detected, the 869 blocks the operation of the output
relay 1 “Trip” and operates a selected auxiliary output relay. The same auxiliary output
relay has to be wired to the upstream switching device (usually a breaker) that is rated to
interrupt the fault current. Finally, if the current has not decreased below the contactor
rated current for a programmable time, the block to the output relay 1 is removed.
The sequence described above is intended to pr
event damages to the contactor. In order
to use this sequence, the user has to configure the IOC 1 protection element, build a
FlexLogic Equation and configure output relays “Trip” and “Auxiliary”.
In the example below, Auxiliary output relay 4 has to be wired to the upstream switching
device.
1. IOC 1 configuration
Function = Configurable
Input = RMS
Pickup = [Contactor rated current, e.g. 10.000 x CT]
Direction = Disabled
Pickup Delay = [Duration of Trip r
elay block, e.g. 1.000 s]
Dropout Delay = 0.000
Block = Off
Output Relay 4 = Disabled
Events = Enabled
Targets = Latched