INSTALLATION
•
OPERATION
INSTRUCTIONS
I.L. 41-2778
•
MAINTENANCE
TYPE COQ
NEGATIVE SEQUENCE GENERATOR RELAY
CAUTION
Before putting protective
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. I nspect the con
tacts to see that they are clean and can close
properly.
Operate the relay to check the
settings and electrical connections.
APPLICATION
A COQ relay operates to disconnect a genera-
tor from a faulted line before
negative
sequence currents can damage the machine.
CONSTRUCTION AND OPERATION
The type COQ relay consists of an induction
disc type overcurrent element,
a contactor
s�itch, an operation indicator, and a negative
sequence current filter.
OVERCURRENT ELEMENT
This is
operated by
an induction-disc type element
negative
sequence quantities
supplied to an electromagnet in the rear of
the relay.
A voltage is induced in the
secondary coil of this electromagnet by trans
former action of the main coil. Both coils
are located on the center leg of the electro
magnet.
Current flow is from the secondary
coil to coils on the outer legs of the elec
tromagnet. 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.
The vertical shaft is supported to the ele
ment frame by a pin and end stone type bearing
on the lower end and a pin and olive bearing
on the upper end. Both shaft bearings as well
SUPERSEDES I. L. 41-277A
4<])enotes changed from superseded issue.
as their 2djustable pins are removable. A set
screw and nylon plug locks the bottom pin in
position, and a sho�lder nut of the time dial
locks the top pin in position.
Attached to an insulated section of the
disc shaft is a rigid arm holding
a
small
silver hemisphere.
This combination of arm
and silver hemisphere comprises the moving
contact assembly which is part of an elec
trical circuit.
This circuit is completed by
a spiral spring with one end soldered to the
rigid arm and the other end fastened to
a
slotted spring adjuster which in turn fastens
to the element frame.
The stationary contact assembly consists of
a silver contact attached to the free end of
the leaf spring.
This spring is fastened to a
Micarta block mounted on the element frame. A
small set screw permits the adjustment of con
tact follow.
Contactor Switch
This switch is a small d-e
solenoid type
conneqted in series with the main contacts of
the
relay
and the trip coil of a breaker.
When the relay contacts close,
the solenoid
coil becomes energized and moves a cylindrical
plunger upward.
A silver disc is mounted on
the plunger's lower end,
and it bridges three
contacts which are in parallel with the main
contacts.
The main contacts are thereby re
lieved of the duty of carrying
tripping cur
rents.
These three contacts remain closed
until the trip circuit is opened by an auxili
ary switch on the breaker.
Operation I ndicator
The operation indicator is a small solenoid
EFFECTIVE APRIL 1957
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