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Effective:

May 1997

Supersedes I.L. 41-161H Dated July 1984

( | ) Denotes Change Since Previous Issu

CAUTION

Before putting protection 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 can close prop-

erly. Operate the relay to check the settings

and electrical connections.

APPLICATION

The COQ is used to prevent a synchronous machine

from being damaged due to negative sequence fault

currents. Two varieties are available, as shown in

Figures 2 and 3, depending upon whether the neutral

can be formed at the COQ or whether the neutral

must be formed elsewhere. (See external schematic,

Figures 8 and 9.)

CONSTRUCTION AND OPERATION

The COQ consists of an induction disc overcurrent

unit, a negative sequence filter, and an indicating

contactor switch (ICS).

2.1.

Overcurrent Unit

This is an induction-disc type unit operated by nega-

tive sequence quantities supplied to an electromag-

net in the rear of the relay. A voltage is induced in the

secondary coil of this electromagnet by transformer

action of the main coil. Both coils are located on the

center leg of the electromagnet. Current flow is from

the secondary coil to coils on the outer legs of the

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.

ABB Power T&D Company Inc.

Relay Division

Coral Springs, FL 33065

Negative Sequence Generator Relay

electromagnet. The reaction between the outer leg

coil fluxes and the main coil flux creates an operating

torque on a spiral shaped aluminum disc mounted on

a vertical shaft.

2.2. Indicating Contactor Switch Unit (ICS)

The dc indicating contactor switch is a small clapper

type device. A magnetic armature, to which leaf-

spring mounted contacts are attached, is attracted to

the magnetic core upon energization of the switch.

When the switch closes, the moving contacts bridge

two stationary contacts, completing the trip circuit.

Also during this operation two fingers on the arma-

ture deflect a spring located on the front of the

switch, which allows the operation indicator target to

drop. The target is reset from the outside of the case

by a push rod located at the bottom of the cover.

The front spring, in addition to holding the target, pro-

vides restraint for the armature and thus controls the

pickup value of the switch.

3.1. Overcurrent Unit

The COQ negative sequence relay is available with

the following negative sequence current taps:

These tap values represent the current transformer

secondary amperes which correspond to one per unit

generator current. At these values of negative

sequence current, the moving contact will leave the

time dial stop and reach the stationary contacts in a

time as determined by the time dial setting and is as

shown by Figure 7. For example, with a time dial

Type COQ

(50/60 Hertz)

CHARACTERISTICS

3.25

3.5

3.8

Instruction Leaflet

I.L. 41-161J

4.2

4.6

5.0