TY P ES CA- 1 6 AND CA-26 R E LAYS
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FEEDER
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PERCEIITAIE O I FFEREIIT IAL IELAY, TYPE
CA-ll
acs - IIIDICATIIIO conActoR s•ncH
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OP - OPERATING COIL
(BOTTOM L.N.ELEMEIIT)
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PAIRED RESTI:A UIT COIL
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(BOTTOM R . N . ELENt:IIT)
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PAIRED RESTUIIIT COIL
(TOP L.a. ELEMEIT)
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PAIRED RESTitAIMT COIL
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AUX ILIAIY Tllii'PIIG IELAT, TYI'E
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187A425
Fig.
9.
External Schematic of the Type C A- 7 6 Relays for
Protection of a Six Circuit B us w ith Three Feeder
Groups
Burden of operating circuit
VOLT AMPERES
Variable (See Fig. 7)
Continuous rating 8 amperes
1 second rating 280 amperes
C O N N E C T I ON S
To determine the a-c connections , identify each
primary circuit as either a "sourc e " or "feeder ' ! As
defined here, a feeder contriqutes only a small por
tion of the total fault-current contribution for a bus
fault. Otherwis e, the circuit is a source. Next lump
a number of feeders into a "feeder group " by p arallel
ing feeder CT's, taking the precaution that each
feeder group has l ess than 14 amperes load current
(restraint coil continuous rating). Also each feeder
group should not contribute more than 10% of the
total phase or ground-fault current for a bus fault.
Connect per Fig. 8 with three or four bus "cir
cuit. ' ' The term ' 'circuit'
•
refers t o a source or t o a
feeder group. For example , assume a bus consisting
of 2 sources and 6 feeders. Further , assume that the
feeders are lumped into 2 feeder groups . The bus now
reduces to four circuits .
6
If the bus reduces to more than four circuits ,
parallel source-circuit CT's or source- and feeder-cir
CT's until only four circuits remain. Then connect
these four sets of CT's to the rel ays p er Fig. 8. The
exception to this rule occurs when the application
consists of three feeder groups. Then, Fig. 9 applies .
With 3 feeder group s and more than 3 sources,
parallel source CT's until the applic ation reduces
to 6 circuits; then, connect to the relays per Fig.
9 .
S E T T I NG
CAL C U LAT I O N S
No calcul ations are re quired to set the CA- 16 and
CA- 26 relays.
S E T T I NG T H E R E LAY
No settings are required on either the CA- 16 or
the CA- 26 main units.
I n d i c at i ng C o ntactor S w i tc h ( I C S )
No setting is required on the ICS unit except the
selection of the 0 . 2 or 2 . 0 ampere tap setting. This
selection is made by connecting the lead located i n
front of the tap block to the desired setting by means
of the connecting screw. When the relay energizes a
125 or 250 volt d-e WL relay switch o r e quiva
lent, use the 0 . 2 ampere tap ; for 48 volt d-e applic a
tions set relay i n 2 tap and use W L relay coil S1t304-
C209G0 1 or e quival ent.
I n d i c a t i n g I n s t a n t a n e o u s T r i p ( l i T )
Since the minimum and maximum markings on the
scale only indicate the working range of the cor e
screw must be adjusted to the value of pick-up de
sired. It is recommended that the liT be set to pick
up at a value of current that is equal to the max
imum rms symmetric al external fault current to the
relay.
I N S TA L L AT I O N
The relays should b e mounted o n a switchboard
panel or their e quivalent in a location fre e from dirt ,
moisture, excessive vibration , and heat. Mount the
relay vertically by means of the four mounting hol e s
o n the flange for semi-flush mounting o r by means of
the rear mounting stud or studs for projection mount
ing. Either a mounting stud or the mounting screws
may be utilized for grounding the relay. The elec
trical connections may be made directly to the ter
minals by means o f screws for steel p anel mounting
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