ABB Relion 670 series, Technical Reference Manual

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5.1.1 Introduction
5.1.1.1 Line differential protection, 3 or 6 CT sets L3CPDIF, L6CPDIF
Line differential protection applies the Kirchhoff's law and compares the currents
entering and leaving the protected multi-terminal circuit, consisting of overhead power
lines, power transformers and cables. It offers phase-segregated true current differential
protection with high sensitivity and provides phase selection information for single-
pole tripping.
The three terminal version is used for conventional two-terminal lines with or without
breaker-and-a-half circuit breaker arrangement in one end, as well as three terminal
lines with single breaker arrangements at all terminals.
IED IED
Protected zone
Communication Channel
ANSI05000039_2_en.vsd
ANSI05000039 V2 EN
Figure 46: Example of application on a conventional two-terminal line
The six terminal versions are used for conventional two-terminal lines with breaker-and-
a-half circuit breaker arrangements in both ends, as well as multi terminal lines with up
to five terminals.
Section 5
1MRK505222-UUS C
Differential protection
122
Technical reference manual