TYPE COQ RELAY
CONTACTOA SWI
/-TEST
SJI'ITCH
- OVERCURRE!ff ELEMENT
3 Hl.wDIM>'S
TEST JACK
BAS£ 7£RM9,
FRo.-vr
CHA.S�JS OPERATED
26-D-1428
ShORT!'-"'
SW/TCH
Fig. 1-Internal Schematic Of The COQ Relay In
FT
Case.
coil connected in the trip circuit.
When the
coil is energized a spring-restrained armature
releases the white target which falls by
gravity to indicate completion of the trip
circuit.
The indicator may be reset from out
side of the case.
Negative Sequence Current Filter
The negative sequence current filter con
sists of a reactor and an adjustable resistor.
These elements are connected in such a manner
that the output of the filter is proportional
to the negative
sequence input.
CHARACTERISTICS
The COQ negative sequence relay is available
with the following negative sequence current
taps:
3
3-25
3-5
4.2
4.6
5.0
These tap values
represent
the current
transformer secondary amperes which corres
pond to one per unit generator current.
At
these values of negative sequence currents,
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 as shown by Fig.
3·
For example, with
a
2
time dial setting of
"4"
the relay will close
its contacts in
30
seconds with the above tap
currents applied to the relay.
As shown by the curves of figure
2,
the
relay's characteristic is defined by a genera-
tor characteristic
I�T
=
K.
The relay charac
teristic is such that it coincides with the
generator characteristic at l per unit nega
tive sequence current but at higher values of
negative sequence current,
the relay charac
teristic is substantially parallel and slight
ly less than the generator characteristic.
In
this manner,
a suitable margin of safety is
obtained between the two characteristics.
Figure
2
defines the relay characteristics
for two generators - one with a
permissible
constant of
"3
0 " and the other with a constant
of
"90".
The time dial settings for these
constants are
"4"
and
"11"
Similar protection for
other
I
�
T constants between
"30"
respectively.
generators with
and
"90"
is ob-
tained by settings of the time dial. Figure
3
shows
the necessary ti�e
dial settings for
various
I�T
constants.
By referring to this
figure, the time dial can
be
set so that the
relay protects
different generators whose
l�T
constants range from
"30"
to
"90".
Typical operating characteristics
relay are shown in flgure
4.
of the
*
Minimum pickup of
t�e relay is approximately
.G per
u�it.
The
burdens
and thermal ratings are listed
under Energy Requirements.
3-25
Circuit
The main
contacts will
safely
close
30
amperes at
250
V.
d-e, and the switch contacts
will safely carry this current long enough
to
trip
a
breaker.
As shipped from the factory,
the operation
indicator and the contactor switch are con-
nected in parallel.
This circuit is suitable
for all trip currents above
2"25
amperes d-e.
I f the trip current is less than
2.25
amperes,
there is no need for the contactor s witch and
it should be dlsconnected.
To disconnect the
coil remove the short lead to the coil on the
front stationary contact of the co�tactor
switcho
This lead should be
fastened
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