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COV Voltage Controlled Overcurrent Relay

the slow-release telephone relay over a range of 80

to 100 volts. The contacts open to de-energize the

telephone relay if the voltage is higher than the set

value. The drop-out ratio of the unit is 98% or higher.

Relays are shipped from the factory with a 90 volt

setting.

3.3

TRIP CIRCUIT

The main contacts will safely close 30 amperes at

250 volts dc and the seal-in contacts of the indicating

contactor switch will safely carry this current long

enough to trip a circuit breaker.

3.4

TRIP CIRCUIT CONSTANTS

Indicating Contactor Switch Coils.

Ampere Pickup

0.2

1.0

2.0

4.0 RELAY SETTINGS

CAUTION

In order to avoid opening current transformer cir-

cuits when changing taps under load, start with

RED handles FIRST and open all switchblades.

Chassis operating shorting switches on the case

will short the secondary of the current trans-

former. Taps may then be changed with the relay

either inside or outside the case. Since the tap

block screws carry operating current, be sure

that the screws are turned tight. Then reclose all

switchblades making sure the RED handles are

closed LAST.

4.1

OVERCURRENT UNIT (CO)

The overcurrent unit setting can be defined by tap

setting and time dial position or by tap setting and a

specific time of operation at some current multiple of

the tap setting (e.g. 4 tap setting, 2 time dial position

or 4 tap setting, 0.6 seconds at 6 times tap value cur-

rent). The tap setting is the minimum current required

to make the disc move.

To provide selective circuit breaker operation, a mini-

mum coordinating time of 0.3 seconds plus circuit

breaker time is recommended between the relay

being set and the relays with which coordination is to

Ohms dc Resistance

8.5

0.37

0.10

be effected.

The connector screw on the terminal plate above the

time dial makes connections to various turns on the

operating coil. By placing this screw in the various

terminal plate holes, the relay will respond to multi-

ples of tap value currents in accordance with the var-

ious typical time-current curves.

The factory adjustment of the CO unit contacts

provides a contact follow. Where circuit breaker

reclosing will be initiated immediately after a trip by

the CO contact, the time of the opening of the con-

tacts should be a minimum. This condition is

obtained by loosening the stationary contact mount-

ing screw, removing the contact plate and then

replacing the plate with the bent end resting against

the contact spring.

For double trip relays, the upper stationary contact is

adjusted such that the contact spring rests solidly

against the back stop. The lower stationary contact is

then adjusted such that both stationary contact make

contact simultaneously with their respective moving

contact.

4.2

VOLTAGE UNIT (V)

The voltage unit spring calibration is set to close its

contact when the applied voltage is reduced to 80

volts. The voltage unit can be set to close its contacts

from 80 volts to 100 volts by adjusting the resistor

located at the top left of the voltage unit. The spiral

spring is not disturbed when making any setting other

than the calibrated setting of 80 volts.

4.3

INDICATING CONTACTOR SWITCH (ICS)

There are no settings to make on the indicating con-

tactor switch (ICS).

5.0 INSTALLATION

The relays should be mounted on switchboard pan-

els or their equivalent in a location free from dirt,

moisture, excessive vibration and heat. Mount the

relay vertically by means of the four mounting holes

on the flange for the semi-flush type FT case. The

mounting screws may be utilized for grounding the

relay. External toothed washers are provided for use

in the locations shown on the outline and drilling plan

to facilitate making a good electrical connection

between the relay case, its mounting screws and the

relay panel. Ground wires should be affixed to the

mounting screws as required for poorly grounded or

insulated panels. Other electrical connections may

be made directly to the terminals by means of screws

41-116.1C