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GEK-1253E
FAULT DETECTOR RELAY
TYPES CHC11A21 AND UP, CHC11811 AND UP
INTRODUCTION
The CHCllA relay is a complete three-phase and ground, multicontact, high-
speed nondirectional overcurrent relay.
The relay consists of an induction-cup
unit for multiphase faults and a small hinged-armature unit for ground faults.
Two
targets and four electrically separate contacts are available,
and the stud
arrangement is such that complete flexibility of application is obtainable.
These
units are identified in Figure I by nomenclature used throughout the text.
Within
its current-carrying capabil ity, the induction-cup unit of THE CHCllA RELAY IS
DESIGNED FOR CONTINUOUS OPERATION IN THE PICKED-UP POSITION.
The CHCIIB is similar to the CHCIIA except that the auxiliary telephone relay
"AII unit has a dual rating.
The desired rating is selected by a toggle switch
mounted on the front of the relay.
APPLICATION
The CHCIIA relay may be applied wherever a high-speed fault detector is
requ ired.
However, because it has four e 1 ectri ca 11y separate contacts and can be
operated continuously in the picked-up position, it is particularly well suited for
applications as a fault selector in circuit-breaker-failure back-up schemes.
In
these schemes, the CHellA relay is used to detect the failed circuit breaker, and
to select the back-up breakers to be tripped in order to isolate the fault.
In general, the cup unit or phase-fault detector (PFD) would be used to detect
three-phase, phase-to-phase and double-phase-to-ground faults, while the hinged-
armature or ground-fault detector (GFD) unit would detect single-phase-to-ground
faults
if
desired.
In this respect, the hinged-armature unit is more sensitive
than the cup unit.
Typical external connections for the CHellA relay are shown in
Figure
11.
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 [or the purchaser's
purposes, the matter should be referred to the General Electric Company.
To the extent required the products described herein meet applicable ANST, TEEE and NEMA
standards; but no such assurance is given with respect to local codes and ordinances because they vary greatly.
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