ABB Relion 670 Series Technical Reference Manual page 136

Line differential protection ansi

Hide thumbs Also See for Relion 670 Series:

Table of Contents

Differential protection

The second analysis is the 2

Occurrence of these harmonics over a level that is set separately for each one will

block tripping action from the biased slope evaluation.

The third analysis is the negative sequence current analysis. Effectively this is a fault

discriminator that distinguishes between internal and external faults. It works such that

the phase angle of the negative sequence current from the local end is compared with

the phase angle of the sum of the negative sequence currents from the remote ends. The

characteristic for this fault discriminator is shown in figure 53, where the directional

characteristic is defined by the two setting parameters IminNegSeq and NegSeqRoa.

If one or the

currents is too

low, then no

is done, and

IEC05000188 V3 EN

Operating characteristic of the internal/external fault discriminator

Reference direction of currents is considered to be towards the line. Thus, when both

currents to be compared have this direction, the phase difference between them will

ideally be zero. In the opposite case, when one current is entering and the other is

leaving the protected object, the phase difference will ideally be 180 degree. In case

either the local or the sum of the remote negative sequence currents or both is below

the set level, the fault discriminator will not make any fault classification and the value

120 degree is set. This value is then an indication that negative sequence directional

comparison has not been possible to make, and it does not mean classification as

external fault.

harmonic analysis on the differential current.

1MRK505222-UUS C

Internal/external

fault boundary

en05000188-3-en.vsd

Technical reference manual

Relion red670