GE Multilin 850 Instruction Manual page 529

CHAPTER 4: SETPOINTS
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850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
fault causes one of the phases to have high current. Similarly, the minimum starting
current supervision ensures that at least one of the phases need to be higher than the
minimum value in order to detect CT disconnection problems.
Path: Setpoints > Control > CT Supervision > CT Supervision 1(X)
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
MAX CURRENT SUPERVISION
Range: 0.050 to 30.000 x CT in steps of 0.001
Default: 1.500 x CT
This setting applies to sequence, differential, and symmetry check. It supervises each
check function with maximum load current condition. If the phase magnitude of any of
the three phases or I
max
This avoids nuisance alarms under fault conditions and unnecessary blocking of
protection elements during faults.
PICKUP DELAY
Range: 0.000 to 6000.000 s in steps of 0.001
Default: 0.000 s
The pickup delay setting applies to sequence, differential, and symmetry check. It adds
an additional delay between pickup and operate of the element. This is a common
setting for the whole element but each check runs its individual timer depending on their
time of pickup.
If the CT Supervision is used for blocking instantaneous current protection elements, the
pickup delay should be coordinated to allow blocking of the fastest current element.
CTS detection using the Sequence Check Method
SEQUENCE CHECK
Range: Disabled, Enabled
Default: Disabled
This setting enables the sequence check function. The sequence check uses zero
sequence voltage, zero sequence current and measured ground current.
SEQ 3I0 PKP
Range: 0.050 to 30.000 x CT in steps of 0.001
Default: 0.100 x CT
This setting is part of the sequence check and it represents the threshold for zero
sequence current measurement. This zero sequence current is calculated from the set of
3 Phase CTs.
is above this setting, the respective check function is blocked.
CONTROL
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