ABB Power T&D Company Inc.
Relay Division
Coral Springs, FL 33065
Instruction Leaflet
All possible contingencies which may arise during installation, operation or maintenance, and all details and
variations of this equipment do not purport to be covered by these instructions. If further information is desired
by purchaser regarding this particular installation, operation or maintenance of this equipment, the local ABB
Power T&D Company Inc. representative should be contacted.
Printed in U.S.A
.
41-116.1A
Type COV
Voltage Controlled Overcurrent
Relay for Class 1E Applications
Supersedes I.L. 41-116.1 dated May 1981
( | ) Denotes Change Since Previous Issue
Before putting relays into service, remove all
blocking which may have been inserted for the
purpose of securing the parts during shipment,
make sure that all moving parts operate freely,
inspect the contacts to see that they are clean
and close properly, and operate the relay to check
the settings and electrical connections.
1. APPLICATION
These relays have been specially designed and
tested to establish their suitability for Class 1E appli-
cations. Materials have been selected and tested to
insure that the relays will perform their intended func-
tion for their design life when operated in a normal
environment as defined by ANSI standard C37.90-
1989, when exposed to radiation levels up to 10
4
rads, and when subjected to seismic events produc-
ing a Shock Response Spectrum within the limits of
the relay rating.
“Class 1E” is the safety classification of the electric
equipment and systems in nuclear power generating
stations that are essential to emergency shutdown of
the reactor, containment isolation, cooling of the reac-
tor, and heat removal from the containment and reac-
tor, or otherwise are essential in preventing significant
release of radioactive material to the environment.
The type COV relay is applicable where it is desired
that an overcurrent unit be set to operate on less than
full load current when the voltage falls below a prede-
termined value, and it is desired not to operate for any
magnitude of current when the voltage is above the
predetermined value. A typical application is overcur-
rent back-up protection for generators.
This instruction leaflet applies to the following types
of relays:
Type COV-6
Definite Minimum Time Relay
Type COV-7
Moderately Inverse Time Relay
Type COV-8
Inverse Time Relay
Type COV-9
Very Inverse Time Relay
Type COV-11
Extremely Inverse Time Relay
2. CONSTRUCTION AND OPERATION
The relay consists of an overcurrent unit, a voltage
unit with adjustable resistor, an indicating contactor
switch unit, an indicating instantaneous trip unit when
required and a slow-release telephone type relay, “T”
(see Figure 1).
2.1. OVERCURRENT UNIT (CO)
The electromagnets for the types COV-6, COV-7,
COV-8 and COV-9 relays have a main tapped coil
located on the center leg of an “E” type laminated
structure that produces a flux which divides and
returns through the outer legs. A shading coil causes
the flux through the left leg to lag the main pole flux.
The out-of-phase fluxes thus produced in the air gap
cause a contact closing torque.
The electromagnet for the type COV-11 relay has a
main coil consisting of a tapped primary winding. Two
identical coils on the outer legs of the lamination
structure are connected to the main coil secondary in
combination of all the fluxes produced by the electro-
!
CAUTION
Effective:
September 1995
