GEH-1791
SYNCHRONISM-CHECK RELAYS
TYPE IJS
INTRODUCTION
The Type IJS relays are of the induction-disk construction, and are intended for use
as synchronism-check relays.
These relays have two shaded-pole U-magnet driving elements acting on opposite sides
of a single rotating disk.
{See Figure 3. )
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 IJS51A relay has a seal-in unit mounted to the left of the disk shaft,
which operates when the main contacts close.
The Type IJS52A relay does not have a seal-in unit, and is used primarily as an
auxiliary to the Type GES Synchronizing relay as described below.
APPliCATION
The Type IJS relay is applicable as a synchronism-check relay to permit closure of a
circuit breaker only when the frequency difference is negligible or is
0
due to the
two sources which energize it being interconnected elsewhere.
The IJS51A should be used where a target-seal-in unit is required; otherwise use the
IJS52A.
In such an application, the voltages may be considerably out of phase due to load
transfer around the loop that is open at the breaker controlled by the relay.
Forms
of the relay are available with a rated calibration range up to
600;
but for
settings over 200 consideration should be given to the resulting generator stresses
at the instant of closure through existing system impedances, as in any other
situation involving out-of-phase closure.
On systems where the two sides of a given breaker may or may not be interconnected
elsewhere at any given moment when paralleling is desired, the GES or GXS is used
for synchronising when a finite frequency difference exists; and the IJS is used at
the same location for synchronism check when the frequency difference is negligible
or
0
due to the existence of an interconnection elsewhere.
In this application, the
IJS contacts are connected in parallel with those of the GES or GXS.
These instructions do not purport to cover all details or variations in equipment nor provide for every
possible contingency to be met in connection with installation, operation or maintenance. Should further
information be desired or should particular problems arise which are not covered sufficiently for the
purchaser's purposes, the matter should be referred to the General Electric Company.
To the extent required the products described herein meet applicable ANSI, IEEE and NEMA
standards; but no such assurance is given with respect to local codes and ordinances because they vary
greatly.
3
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