GE MiCOM P40 Agile User Manual

10 FEEDERS WITH IN-ZONE TRANSFORMERS
A transformer feeder comprises a transformer directly connected to a transmission circuit without the intervention
of switchgear. Although separate current transformer inputs may be available to allow separate overlapping zones
of protection for the transformer and the feeder this is not always the case and the transformer and the feeder
must be treated and protected as a single item of plant for protection. The integration of in-zone power
transformers into unit feeders causes further complications for current differential protection:
● Phase shift and possible imbalance of signals across the transformer
● Transfer of earth fault current by the transformer
● Magnetising Inrush current
● Overfluxing
This product therefore provides facilities to deal with the above issues by providing:
● CT compensation for phase shifts and imbalances across the transformer
● Zero sequence compensation.
● Magnetising Inrush detection and restraint
● Second harmonic blocking.
● Overfluxing detection and restraint
● Fifth harmonic blocking.
To make these available you need to enable the differential protection for an in-zone power transformer. This is
done on a per-setting group basis. The phase differential element (Phase Diff) for the setting group concerned
must be enabled.
To enable the transformer feeder protection you set the Compensation cell in the CURRENT DIFF settings to
Transformer.
10.1
CT PHASE CORRECTION
To compensate for any phase shift between two windings of a transformer, it is necessary to provide phase
correction. Phase correction is provided by specifying the vector group using the Vectorial comp setting in the
CURRENT DIFF column.
The phase compensation options are listed in the table below:
Setting Phase shift Action
Yy0 0 Do nothing
Yd1 30 lag
Ia = (IA - IC) / √3
Ib = (IB - IA) / √3
Ic = (IC - IB) / √3
Yy2 60 lag
Ia = -IC
Ib = -IA
Ic = -IB
Yd3 90 lag
Ia = (IB - IC) / √3
Ib = (IC - IA) / √3
Ic = (IA - IB) / √3
Yy4 120 lag
Ia = IB
Ib = IC
Ic = IA
Yd5 150 lag Yd11 and Invert
Chapter 6 - Current Differential Protection P543i/P545i
114 P54x1i-TM-EN-1

GE MiCOM P40 Agile Specifications

General

Brand	GE
Model	MiCOM P40 Agile
Category	Control Unit
Language	English