D90
Chapter 15: Theory of operation
The D90
Distance element arming logic
PLUS
D90
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Plus
Line Distance Protection System
Theory of operation
This section describes the basic theoretical principles behind the operation of D90
Plus
distance elements
The distance element is composed of two separate algorithms. The first is a conventional
frequency domain (phasor) algorithm based on the UR-series D60 implementation. The
second is a time domain algorithm that achieves sub-cycle operating times. The two
algorithms run in parallel and each can independently issue a trip command.
The distance element arming logic grants permission to the time domain algorithm only if
all of the following conditions are met for five cycles prior to a disturbance.
•
Zero-sequence current is less than 0.2 pu.
•
Negative-sequence current is less than 0.2 pu.
•
Zero-sequence voltage is less than 0.2 pu.
•
Negative-sequence voltage is less than 0.2 pu.
Plus
Figure 462: D90
distance algorithm
Plus
.
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