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T Y P E CO C I RCU I T O P E N I NG R E LAY
CO RELAY
(FRONT i i EW )
Fig. 1 0.
D i agram
of
Test
Opening CO R e lay in the Type F T2 1 C a s e.
S E T T I NGS
CO UNIT
The
overcurrent unit settings can be defined
either by tap setting and time dial position or by tap
setting and a specific time of operation at some cur
rent multiple of the tap s etting ( e . g . 4 tap setting, 2
time dial position or 4 tap setting , 0 . 6 seconds at 6
times tap value current).
To provide se�ective circuit breaker operation, a
minimum coordinating time of 0 .3 seconds plus cir
cuit breaker time is recommended between the relay
being set and the relays with which coordinaticn is to
be effected.
The connector sc rew on the terminal plate above
the tim e dial makes connections to various turns on
the
operating coil .
By placing thrs screw in the
various terminal plate hol es , the relay will respond to
mul tiples of tap val ue currents in accordance with
the various typical time-current curve s .
CAUTION
Since the tap block connector screw carries oper
ating current , be sure that the screw is turned tight.
In order to avoid opening the current transformer cir
cuits
when changing taps under load , connect the
spare connector screw in the desired tap position
before removing the other tap screw from the original
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A��Nucr l
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l
NER
STOP
(OPENS
)
TO
( T I M E R STARTS
T I MER
(WHEH SWifCH
( " S " CLOSES
START
•s·
SWITCH
120
VOLTS
60
l83A2 14
CYC.
Connections
for the Circuit
1
2
3
DEi ICE NUN8ER CHART
51 - OVERCURRENT RELAY, TYPE CO
0!
CS - DE- I ON CONTACTOR S W I T C H I N H P E CO RELAY
- OPERA T I ON I N D I CATOR I N
52 - POWER C I RCU I T 8REAKER
TC - 8REAKER TR I P CO I L
F i g . 1 1 .
External Schematic of t h e Circuit Open in g Type
CO R elay for Phase Overcurrent Protection on a
Three Phase System.
tap position.
INSTANTANEOUS RECLOSING
The factory adj ustment of the CO unit contact
provides a contact follow. Where instantaneous circuit
breaker reclosing will be initiated upon the closure
of the CO contact, this contact follow must be elim
inated by loosening the stationar y contact mounting
screw , removing the contact plate and then replacing
the plate with the bent end resting against the con
tact spring .
With this change and the contact mount
ing screw tightened , the stationary contact will rest
solidly against its backstop.
D E ION CONT ACTOR SWITCH (CS)
No setting is required on this unit.
OPERATION INDIC ATOR (OI)
No setting is required on this unit.
}
51
51-1
51
PH. 1
}
P�2
}
P H . 3
TYPE
CO RELAY
183A2 13
13
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