Date Code 20170601
Instruction Manual
SEL-387-0, -5, -6 Relay
Appendix H
Protection Application Examples
Overview
This section provides instructions for setting the SEL-387 Relay protection
functions. Use these application examples to help familiarize yourself with the
relay and assist you with your own protection settings calculations. This
section is not intended to provide a complete settings guide for the relay.
Transformer Winding and CT Connection
Compensation Settings Examples
In electromechanical and solid-state transformer differential relays, the
standard current transformer (CT) configuration was wye connected on the
delta winding of the transformer and delta connected on the wye winding of
the transformer. The CT delta connection was constructed based on the power
transformer delta to compensate for the phase shift that occurred on the
system primary currents because of the power transformer connection. The
CT configuration allowed the currents entering the relay for through-load or
external faults to be 180 degrees out-of-phase so that the phasor sum of the
currents added to zero (no differential current) in an electromechanical
differential relay. Taps on the relay current inputs compensated for magnitude
differences. Modern digital relays perform both the connection (or phase) and
magnitude compensation mathematically so all CTs can be connected in wye.
This section provides a procedure for SEL-387 Relays to determine and set
the Terminal
n
CT connection compensation settings, W
n
CTC (where
n
= 1, 2, 3, or 4), to compensate for the phase shift across the transformer.
Each of the connection compensation settings offer thirteen 3x3 matrices,
CTC(0)–CTC(12), permitting CT connection compensation from 0 degrees to
360 degrees, in increments of 30 degrees, respectively. Refer to
Differential, Restricted Earth Fault, Thermal, and Overcurrent Elements
(
) for each of the compensation matrices. When applied on a system
with an ABC phase rotation, these matrices perform phase angle correction in
a counterclockwise (CCW) direction in multiples of 30 degrees, as shown in
. For a system with an ACB phase rotation, the direction of
correction is clockwise (CW). See
Special Cases
for a compensation settings
example on a system with an ACB phase rotation.
NOTE: In this settings guideline, the
term “phase rotation” is synonymous
with “phase sequence.” This settings
guideline uses “phase rotation” to be
consistent with the relay Global
setting, PHROT.
Содержание SEL-387-0
Страница 6: ...This page intentionally left blank ...
Страница 12: ...This page intentionally left blank ...
Страница 50: ...This page intentionally left blank ...
Страница 200: ...This page intentionally left blank ...
Страница 248: ...This page intentionally left blank ...
Страница 380: ...This page intentionally left blank ...
Страница 422: ...This page intentionally left blank ...
Страница 440: ...This page intentionally left blank ...
Страница 458: ...This page intentionally left blank ...
Страница 516: ...This page intentionally left blank ...
Страница 540: ...This page intentionally left blank ...