Installation - Westinghouse CO Instructions Manual

When the chassis is to be put back in the case,
the above procedure is to be followed in the re­
versed order. The elongated red handle switch
should not be closed until after the chassis has
been latched in place and all of the black handle
switches closed.
Electrical Circuits :-Each
connects through a test switch to the relay elements
in the chassis as shown on the internal schematic
diagrams. The relay terminal is identified by
numbers marked on both the inside and outside
of the base. The test switch positions are identified
by letters marked on the top and bottom surfaces
of the moulded blocks. These letters can be seen
when the chassis is removed from the case.
The potential and control circuits thru the relay
are disconnected from the external circuit by open­
ing the associated test switches.
current test switch short-circuits the current
transformer secondary and disconnects one side
of the relay coil but leaves the other side of the coil
connected to the external circuit thru the current
test jack jaws. This circuit can be isolated by
inserting the current test plug (without external
connections) , by inserting the ten circuit test plug,
or by inserting a piece of insulating material ap­
proximately 3\ " thick into the current test jack
jaws. Both switches of the current test switch
pair must be open when using the current test
plug or insulating material in this manner to
short-circuit the current transformer secondary.
A cover operated switch can be supplied with its
contacts wired in series with the trip circuit. This
switch opens the trip circuit when the cover is
removed. This switch can be added to the existing
type FT cases at any time.
The relays can be tested in service,
Testing :-
in the circuits isolated or out of the case as follo\',·s :
Testing In Service-
can be inserted in the current test jaws after open­
ing the knife-blade switch to check the current
through the relay. This plug consists of two con­
d ucting strips separated by an insulating strip. The
ammeter is connected to these strips by terminal
screws and the leads are carried out through holes in
the back of the insulated handle.
Voltage between the potential circuits can be
measured conveniently by clamping * 2 clip leads
on the projecting clip lead lug on the contact jaw.
:
-
With all blades in the full
Testing In Case
open position, the ten circuit test plug can be
inserted in the contact jaws.
relay elements to a set of binding posts and com­
pletely isolates the relay circuits from the external
connections by means of an insulating barrier on
the plug. The external test circuits are connected
to these binding posts. The plug is inserted in the
bottom test jaws with the binding posts up and in
the top test switch jaws with the binding posts
clown.
Types CO and COH Overcurrent Relays
terminal in the base
Opening the
The ammeter test plug
This connects the
The external test circuits may bE made to the
relay elements by * 2 test clip leads instead of the
test plug. When connecting an external test
circuit to the current elements using clip leads,
care should be taken to see that the current test
jack jaws are open so that the relay is completely
isolated from the external circuits.
means for isolating this circuit are outlined above,
under " Electrical Circuits."
Testing Out o f Case :-
moved from the base, relay elements may be
tested by using the ten circuit test plug or by '/1: 2
test clip leads as described above.
calibration is made with the chassis in the case
and removing the chassis from the case will change
the calibration values of some relays by a small
percentage. I t is recommended that the relay be
checked in position as a final check on calibration.

INSTALLATION

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 two mounting
studs for the standard cases and the type FT
projection case or by means of the four mounting
holes on the flange for the semi-flush type FT
case. Either of the studs or the mounting screws
may be u tilized for grounding the relay.
electrical connections may be made direct to the
terminals by means of screws for steel panel mount­
ing or to terminal studs furnished with the relay
for ebony asbestos or slate panel mounting. The
terminal studs may be easily removed or inserted
by locking two n uts on the studs and then turning
the proper nut with a wrench.
Because the circuit-opening relay contacts short
circuit the trip coil , it is important that the relay
be mounted where it will not be subject to shocks
which may jar the contacts open and thereby allow
current to flow through the trip coil. Trouble of
this kind can be avoided by preventing j ars to the
switchboard and also by setting the trip coil high
enough so that it will not operate on normal load
current. This is an extra safeguard so that there
there is no danger from even an excessive shock
unless the current is also heavy.
Typical external connections are shown in
Figures 18 to 22. When using the circuit-opening
relays for phase protection, ground protection may
be secured by using a low-energy circuit-closing
relay operating on a-c. voltage trip coil, as shown
in Figure 22.
SETTINGS
There are two settings-namely the current value
at which the relay closes its contacts and the time
required to close them. When the relay is to be
used to protect equipment against overload, the
setting m ust be determined by the nature of the
load , the magnitude of the peaks and the frequency
of their occurrence.
7
Suggested
With the chassis re­
The factory
The