ABB Automation Inc.
Substation Automation and Protection Division
Coral Springs, FL
Instruction Leaflet
All possible contingencies which may arise during installation, operation or maintenance, and all details and
variations of this equipment do not purport to be covered by these instructions. If further information is desired
by purchaser regarding this particular installation, operation or maintenance of this equipment, the local ABB
Power T&D Company Inc. representative should be contacted.
41-337.31B
Printed in U.S.A
.
Effective: February 1995
Supersedes I.L. 41-337.31A, Dated February 1983
(
) Denotes Change Since Previous Issue
Before putting relays into service, remove all
blocking which may have been inserted for
the purpose of securing the parts during
shipment, make sure that all moving parts
operate freely, inspect the contacts to see
that they are clean and close properly, and
operate the relay to check the settings and
electrical connections.
1.0
APPLICATION
These relays have been specially designed and
tested to establish their suitability for class 1E appli-
cations. Materials have been selected and tested to
insure that the relays will preform their intended func-
tion for their design life when operated in a normal
environment as defined by ANSI standard C37.90-
1978, when exposed to radiation levels up to 10
4
rads, and when subjected to seismic events produc-
ing a Shock Response Spectrum within the limits of
the relay rating.
“Class 1E” is the safety classification of the electric
equipment and systems in nuclear power generating
stations that are essential to emergency shutdown of
the reactor, containment isolation, cooling of the reac-
tor, and heat removal from the containment and reac-
tor, or otherwise are essential in preventing significant
release of radioactive material to the environment.
The current transformers should not saturate when
carrying the maximum external fault current. This
requirement is met if the burden impedance does not
exceed
where
N
P
= proportion of total ct turns in use
V
CL
= current transformer accuracy class C
voltage
I
ext
= maximum external fault current in secondary
RMS amperes. (let I
ext.
= 100 if max. external
fault current is less than 100A)
R
S
= current transformer secondary finding resis-
tance, ohms
For example, if the 400:5 tap of 800:5 C400 current
transformers are used, N
P
= 400/800 = 0.50, if I
ext.
=
120A, R
S
= 1.0 ohm the burden should not exceed:
The CA-16 relay should not be utilized for transformer
differential applications since it is too sensitive for
overriding the inrush. Likewise the CA-26 relay
should not be used for bus protection with the “four
circuit bus” connections of Figure 6.
2.0
CONSTRUCTION
The type CA-16 relay consists of an indicating con-
tactor switch, autotransformer, three restraint ele-
ments, an operating element, and a sensitive fault
detector.
The principal component parts of the relay and their
location are shown in Figures 1 to 3.
!
CAUTION
N
P
V
C L
I
e xt
·
100
–
(
)
R
s
–
1.33
I
ext
(
)
---------------------------------------------------------
N
P
V
C L
I
e xt
.
100
R
S
–
(
)
–
1.33
I
ext
.
(
)
----------------------------------------------------------- =
0.5
x
400
120
100
–
(
)
x
1.0
–
1.33
x
120
-----------------------------------------------------------------
1.13 ohms
=
Type CA-16
Percentage Differential
Relay for Bus Protection
Class 1E Applications
