pa1rmg current transformers in the same manner as
outlined for single relay per phase applications.
SETTING CALCULATIONS
No calculations are required to set the CA-6
relay.
SETTING THE R ELAY
BUS DIFFERENTIAL RELAY
The external current transformer taps are the
only setting required. Where the d-e time constant
is
0 . 6
cycles or less and where the current trans
former ratio error as a result of a-c saturation
exceeds
5%,
it is recommended that the No.
38
tap
be used.
In all other cases, the No .
1 9
tap is
recommended.
If
the minimum internal fault current is greater
than
. 14
amperes, the pickup of the relay may be
increased by means of the spring adjuster.
The
spring tension can be increased such that a maxi
mum pickup of
.4
amperes can be obtained.
The
pickup current is to be measured when only the
operating circuit is energized.
TRANSFORMER DIFFERENTIAL RELAY
Set the external current transformer tap . The
following settings are recommended for mismatch
of the main current transformers :
Percent
t
Minimum
Minimum
Mismatch
Pickup Setting
Tap
D-5
. 75
Amp .
1 9
5- 10
1 . 00
Amp,
38
10- 15
1. 25
Amp ,
38
t
Includes error due to power transformer tap
changing.
The pickup of the relay is varied by means of
the spring adjuster.
INDICATING CONT ACTOR SWITCH (ICS)
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 in
front of the tap block to the desired setting by means
of the connecting screw. When the relay energizes a
type WL relay switch, or equivalent, use the
0 . 2
ampere tap.
INDICATING INSTANTANEOUS TRIP (liT)
The core screw must be adjusted to the value
1 2
o f pick-up desired. It i s recommended that a pickup
of
100
amperes be used.
I N S T A L L A T I O N
The relays should be mounted on switchboard
panels or their equivalent in a location free from
dirt, moisture, excessive vibration, and heat. Mount
the relay vertically by means of the four mounting
holes on the flange for semi-flush mounting or by
means of the rear mounting stud or studs for projection
mounting. Either a mounting stud or the mounting
screws may be utilized for grounding the relay. The
electrical connections may be made directly to the
terminals by means of screws for steel panel mount
ing or to the terminal studs furnished with the relay
for thick panel mounting. The terminal studs may be
easily removed or inserted by 'locking two nuts on
the stud and then turning the proper nut with a wrench.
For detailed FT case information refer to I.L.
41-076.
The total resistance of the leads, connecting
relay terminals
1 2
and
1 3
to
the R terminals of the
auxiliary current transformer, must not exceed
0.05
ohm.
*
A D J U S T M E N T S A N D M A I N T E N A N C E
The proper adjustments
to
insure correct op era
tion of this relay have been made at the factory. Upon
receipt of the relay no customer adjustments, other
than those covered under "SETTINGS" should be
required.
A c c ep t a n c e C he c k
The following check is recommended t o insure
that the relay is in proper working order. Relays and
transform ers of matching serial numbers should be
connected together. Use ti ght screw connections. No
clip leads should be used. The total resistance of
leads, connecting relay terminals
12
and
13
to the R
terminals of the auxiliary current transform er , must
not exceed
0.05
ohms.
A. M i n i m u m T r i p C urrent
Apply current to the primary of the external
transformer. The relay should operate as follows on
the
19
tap.
1.
Bus Differential Relay
2.
Transformer Differential Relay
0. 145
±
5%
amp.
1 . 0
±
5%
amp .
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