Introduction; Application - GE IJS52D Instructions Manual

GEI-90802
SYNCHRONISM-CHECK RELAY
TYPE IJS52D
INTRODUCTION
The Type IJS52D relays are of the induction-disk construction, and are intended for
use as synchronism-check relays.
The synchronism-check unit has two shaded-pole U-magnet driving elements acting on
opposite sides of a single rotating disk (see Figure 2). One of these, the
operating element, drives the disk in the contact-closing direction, and the other,
the restraining element, drives the disk in the opposite direction. The disk shaft
is restrained by a spiral spring, the purpose being to hold the contacts open when
the relay is de-energized. The motion of the disk is retarded by permanent magnets
(drag magnets) acting on the disk to give a time delay.
The Type IJS52D relay has two telephone-type undervoltage units.
designated as 118 11 and IIlll on Figure 7.
These are
The Type IJS52D relay does not have a seal-in unit, since one is not required in its
normal application.
APPLICATION
The IJS relay is applicable as a synchronism-check relay to permit closure of a
circuit breaker only when the two sources connected to it are correctly synchronized
elsewhere. It determines that synchronism is being maintained by other
incterconnections, and then permits closure of the circuit breaker. See Figure 9
for a typical elementary diagram.
In such an application, the voltages may be slightly out of phase with each other
because of different line and load characteristics. This condition may exist, for
example, where one line is supplying a lagging load through a transformer bank, and
the second is unloaded. The rel ay, however, can be cali bra ted to permi t closure of
the breaker under these conditions if the voltage and the phase-angle differences
are not excessive.
However, the IJS relay cannot discriminate between a very low slip frequency between
systems, and systems in synchronism. Figures 13 and 14 illustrate that the slip
frequency with which the IJS will permit closing increases with increasing closing-
angle settings, and decreases with increasing time-dial settings. In general, the
closing-angle setting is fixed by the maximum angular separation of the systems for
which the IJS must operate, and the slip frequency for which the IJS will operate is
reduced to an acceptable maximum by increasing the time-dial setting.
These
~nstructions do not purport
to
cover ~ll
details or variations in equipment nor
to
provid. for
every possible contingency
to
be
met
in connection with installation, operation
or . .
intenance. Should
further information be desired
or
should particular problems
arise
which
are not covered
sutflcientlg for
the pt,;Ichaser
f
5 purposes, the
1M
tter shoul
d be
referred to the General Electric Company_
To the extent required the products described herein meet applicable ANSI,
IEEE and N£~ standards,
bu
t
no such assurance is gl ven wi th respect to local codes and ordinances because they vary greatly.