T Y P ES CA- 1 6 AND CA- 26 R ELAYS
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AUXILI.UY TUI"riiiG UU.Y, TYI't:
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187A42 5
Fig.
9.
External Schematic of the Type CA- 1 6 Relays for
Protection of a Six Circuit B us w ith Three Feeder
Groups
primary circuit as either a " sourc e " or "feeder • : As
defined here , a feeder contributes only a small por
tion of the total fault-current contribution for a bus
fault. Otherwise, the circuit is a source. Next lump
a number of feeders into a "feeder group " by p arallel
ing feeder C T ' s , taking the precaution that each
feeder group has less 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 b us " c ir
cuit. " The term "circuit" refers t o a source or t o a
feeder group. F or example , assume a bus c onsisting
of 2 sources and 6 feeders. Further , assume that the
feeders are lumped into 2 feeder groups . The bus now
reduces to four circuits .
If
the bus reduces to more than four c ircuits ,
parallel source-circ uit 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 occ urs when the application
consists of thre e feeder gro ups. Then , Fig.
9
applies.
With 3 feeder group s and more than 3 source s ,
p arallel source C T ' s until the applic ation reduces
to 6 circuits; then, connect to the rel ays per Fig.
9.
Fig. 10 sho w s the CA-26 relay connections for a
6
3 circuit bus. Where additional circuits are present
use the Fig. 9 connections; where there are mo re
than three sources the source CT ' s should be p ar
alleled to reduce the effective number of source con
nections to three. The "four- circuit bus" connec
tions of Fig. 8 must not be us ed with the CA-26 .
Otherwise the connection considerations are as
described above for the CA- 16.
S E T T I N G
C A L C U L A T I O N S
No calcul ations are re quired to set the CA- 16 and
CA- 26 rel ays.
S E T T I N G T H E R E L A Y
No settings are required on either the CA- 16 or
the CA- 26 main units.
I n d i c a t i ng C o n t a c t o r S w i tc h ( I C S )
No setting i s re quired on the
res
unit except the
selection of the 0. 2 or 2. 0 ampere tap setting. This
selection is made by connecting the le ad located i n
front of the tap block to the desired setting b y means
of the connecting screw. When the relay energizes a
125 or 250 volt d-e WL relay switch o r equiva
lent , use the 0 . 2 ampere tap ; for 48 volt d-e applic a
tions set relay in 2 tap and use WL relay coil S1t304-
C 209G0 1 or e quivalent.
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 mark ings o n the
scale only indicate the working range of the core
screw must be adjusted to the value of p ick-up d e
sired. It is recommended that the liT be s et to pick
up at a value of current that is equal to the max
imum rms symmetrical e xternal fault current t o the
relay.
I N S T A L L A T I O N
The relays should be mounted on a s witchboard
panel or their e quivalent in a location free 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 b y 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
or to the terminal studs furnished with the relay fo r
thick p anel mounting. The terminal studs may b e
easily removed o r inserted b y locking two nuts o n the
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