41-337.3L
9
125 or 250 Vdc WL relay switch or equivalent, use
the 0.2 ampere tap; for 48 Vdc applications set relay
in 2 tap and use WL relay coil style number 304-
C209G01 or equivalent.
5.3.
Indicating Instantaneous Trip (IIT)
Since the minimum and maximum markings on the
scale only indicate the working range. The core
screw must me adjusted to the value of pick-up
desired. The application of IIT unit is intended to get
faster operating speed for heavy internal faults. For
bus protection, it is recommended the IIT unit be set
higher than 50% of the maximum external fault cur-
rent contributed from the bus and with all circuits in
service. For transformer protection, apply IIT unit
where internal fault current can exceed twice the
maximum total current flowing through the differential
zone for a symmetrical external fault. Set IIT unit at
50% external fault current or higher than transformer
inrush current depending on which is greater.
6. INSTALLATION
The relays should be mounted on a switchboard
panel 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 mount-
ing. 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 mounting 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.
7. ADJUSTMENTS AND MAINTENANCE
The proper adjustments to insure correct operation 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.
7.1.
Acceptance Check
The following check is recommended to insure that
the relay is in proper working order.
A. Minimum Trip Current
Apply current to terminals 12 and 13 of the relay.
The relay should operate as follows:
1. CA-16
0.15 amperes
±
5%
2. CA-26
1.25 amperes
±
5%
B. Percentage Differential Characteristic
Apply 16 amperes to terminals 9 and 19 of the
Sub 2
849A343
Figure 13: Percentage Slope Curve of the CA-16 and CA-
26 Relays with Six Restraint Windings in
Series.
