TYP ES CA- 1 6 AND CA-26
SOIJICE
FEEDER
......._...,
TO
BIE.U:EI
TRIP
COILS
"
8
DEVICE IIUNBEII CIIAiT
...
I
87 - PERCEIHAIE OlfFEREMTIAL IEUY, TYPE CA•l6
ICS - IMDICATIIIG COITACTOfl SWITCH
OP - OPERATUIG COIL
{BOTTOM
L.M.ELEMUl)
R - PAIREO RESTUIIIT COIL
(IOTTOM I . I$ . ElENt:Jil)
S • Pot. IRED RESTUIIT COIL
(TOP
L.M. flEMUr)
T - PAIIED RESTUIIIT COIL
(TOP t.K. ELEMEIIT)
"
TTPE
CA-ll
t[lAf
81 - AUlllllln TIIPP'IIG IEUT, TYPE
wt.
187A425
Fig.
9 .
External Schematic of the Type CA- 1 6 Relays for
Protection of a Six Circuit Bus with Three Feeder
Groups
*
prim ary circuit as either a " source" or " feeder " . As
defined here , a feeder contributes 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 parallel
ing feeder CT ' s, taking the precaution that each
feeder group has less than 14 amperes load c urrent
(re straint coil continuous rating ). Also e ach feeder
group should not contribute more than
10%
of the
total phase or ground-fault current for a bus fault if
figure 9 is to be use d .
Connect p e r Fig. 8 with three o r four bus " c ir
c uit. " The term "circuit" refers t o a source or t o a
feeder group . F or e x ample , 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 circ uits ,
p arallel source-circ uit CT's or source- and feeder-cir
CT' s until only four circuits rem ain. 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,
p arallel source CT' s until the applic ation reduces
to 6 circuits; then, connect to the relays per Fig.
9.
Fig . 1 0 shows th e C A-26 relay conne ctions for a
3
circuit bus . Where additional circuits are pr esent
6
*
use the Fig. 9 connections ; where there are more
than three sources the source CT's should be par
alle lled to reduce the effective number of source con
nections to three . The "four-circuit bus " connec
tions of Fig. 8 are not recommended to be used for
bus protection with the CA-26 since it may have too
much restraint when e nergizing the bus on fault.
Otherwise the connection considerations are as
described above for the C A- 1 6 .
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- 1 6 and
CA- 26 rel ays.
S E T T I N G T H E R E L A Y
No settings are required o n either the CA- 1 6 or
the CA- 26 main units.
I nd i c a t i ng C o nta c t o r S w i t c 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 le ad located i n
front of the tap block to the desired setting by m e ans
of the connecting screw. When the relay e nergizes 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 c oil Slt304-
C 209G0 1 or e quivalent.
I n d i c at 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 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 to the
relay.
I N S T A L L A T I O N
The relays should be mounted on a switchboard
p anel or their e quivalent in a location free from dirt ,
moisture , excessive vibration , and heat. Mount the
relay vertically by m eans of the four mounting hol e s
on the flange for semi-flush mounting o r by m e an s 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 t er
minals b y means of 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 be
easily removed or inserted by locking two nuts on the
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