Sices D-PRO, Техническое руководство

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D-PRO Protection relay Technical Manual 41
Type: Alarm (Maximum differential current)
Related parameters: P.0370 Selection 87G or 87T
P.0371 Minimum differential current threshold (Aac)
P.0372 Maximum differential current threshold (Aac)
P.0373 Threshold for load current slope change (Aac)
P.0374 Slope K1 (%)
P.0375 Slope K2 (%)
P.0376 Maximum differential current delay
To disable: P.0376 =0
The protection is enabled only in case of absence of the disabling digital input and only if the
controller is configured to measure the differential current and selected as 87G (parameter
P.0370
). It’s not possible to activate in the same controller both protection 87G and 87T;
therefore, in case of plants that require both 87G+87T, you will need to use two protection
controllers (to define).
The differential protection 87G is acquired from the comparison of the readings of one set of
three CT on the genset star point and one on the output. It activates on each of the three
phases and it can trigger on each single phase.
Type: Alarm
Related parameters: P.0370 Selection 87G or 87T
P.0371 Minimum differential current threshold (Aac)
P.0372 Maximum differential current threshold (Aac)
P.0373 Threshold for load current slope change (Aac)
P.0374 Slope K1 (%)
P.0375 Slope K2 (%)
P.0376 Maximum differential current delay
To disable: P.0376 =0
The protection is enabled only in case of absence of the disabling digital input and only if the
controller is configured to measure the differential current and selected as 87T (parameter
P.0370
). It’s not possible to activate both protection 87G and 87T in the same controller;
therefore, in case of plants that require both 87G+87T, you will need to use two protection
controllers (to define).
Typically, the differential protection 87T is used if the genset is connected to a step-up
transformer by a rigid supp
ort. It’s similar to the 87G protection, but the reading is acquired
between the CT on the star point and a set of three CT on the transformer (usually in medium
voltage). Therefore, the protection has to consider the current ratios between the two set of
three CT, as well as the characteristics of the step-up transformer. In particular, the
transformation ratio. It activates on each of the three phases and it can trigger on each single
phase.
This protection is expected but not implemented yet.