Phase Comparison Excitation - GE L60 Instruction Manual

OVERVIEW

9.1.4 Phase comparison excitation

9.1.4.1 Description
Before discussing this subject, it is well to consider what takes place in terms of the currents that are available for
comparison when a fault occurs on a power system. The table lists the sequence components of fault current that are
present during the various different kinds of faults while the following figure illustrates the relative phase positions of the
sequence components of fault current for the different kinds of faults and the different phases involved.
Table 9-1: Fault types
Type of fault
Single-Phase-to-Ground
Phase-to-Phase
Double-Phase-to-Ground
Three-Phase
The following figure shows the relative phase positions of the outputs of a positive sequence network, a negative sequence
network, and a zero sequence network all referenced to phase A. The transfer functions of these three networks are given
by the following equations.
9
9-8
Sequence components
Positive Negative
yes yes
yes yes
yes yes
yes no
CHAPTER 9: THEORY OF OPERATION
Zero
yes
no
yes
no
L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL
Eq. 9-1