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3.9 DIFFERENTIAL BIASED TRIP LOGIC

The differential biased trip is affected by both the CT Saturation technique and by the No Gap detection technique.

If the second harmonic block

ing is asserted and either the CT Saturation Detection or No Gap detection technique

is asserted, then the biased differential trip is unblocked.

CT Saturation Detection and No Gap detection act independently from 5th harmonic blocking, however. A biased

differential trip will occur only if the fifth harmonic blocking is not asserted and the bias differential start signal is

asserted. The differential biased trip logic is described below.

V03113

Cross blocking

Enabled

IA2H Diff Start

CT Saturation A

No Gap A

External Fault A

IA5H Diff Start

Id Bias Start A Id Bias Trip A

1 &

IB2H Diff Start

CT Saturation B

No Gap B

External Fault B

IC2H Diff Start

CT Saturation C

No Gap C

External Fault C

IB5H Diff Start

Id Bias Start B Id Bias Trip B

IC5H Diff Start

Id Bias Start C Id Bias Trip C

Figure 46: Differential biased trip logic

Chapter 6 - Transformer Differential Protection P64x

116 P64x-TM-EN-1.3

GE P642 User Manual

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