I.L.
41-923.2
INSTALLATION
•
OPERATION
•
MAINTENANCE
INSTRUCTIONS
TYPE K.A CARRIER .AUXILIARY RELAY
CAUTION
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 proper
ly, and operate the relay to check the settings and
electrical connections.
A P PL ICAT ION
The type
KA
relay is an auxiliary relay u sed in
the distance carrier relaying scheme to block or
prevent instantaneous tripping for faults external to
the line section to which it is applied, and to permit
instantaneous
simultaneous
tripping for internal
faults.
The relay is arranged to respond to indica
tions of fault power and direction provided by the
phase and ground relays, thereby controlling the trans
mission of the carrier signals.
CONSTRUCT ION AND O PERAT ION
The type
KA
relay consists of directional auxili
ary units, receiver and alarm units, and a phase fault
carrier operation indicator. In addition, the type
KA
relay contains a hi�h speed overcurrent unit used to
start carrier transmission for ground faults. The con
struction and operation of the relay units are de
scribed below. Complete details of the operation of
this relay in the distance carrier relaying scheme is
described in I.L.
41-911.
Overcurrent Unit
The overcurrent unit is a product induction cyl
inder type unit.
The time phase relationship of the
two air gap fluxes necessary for the development of
torque is achieved by means of a capacitor connected
in series with one pair of pole windings.
Mechanically, the overcurrent unit is composed of
fotr basic components: a die-cast aluminum frame,
an
electromagnet, a moving element assembly, and a
molded bridge.
The frame serves as the mounting structure for
the magnetic core. The magnetic core which houses
NEW INFORMAT ION
the lower pin bearing is secured to the frame by a
locking nut. The bearing can be replaced,
if
neces
sary, without having to remove the magnetic core
from the frame.
The electromagnet has two pairs of coils.
The
coils of each pair are mounted diametrically opposite
one another. In addition, there are two locating pins.
The locating pins are used to accurately position the
lower pin bearing, which is mounted on the frame,
with respect to the upper pin bearing, which is
threaded into the bridge.
The electromagnet is se
cured to the frame by four mounting screws.
The moving element assembly consists of a
spiral
spring, contact carrying member,
and an
aluminum cylinder assembled to a molded hub which
holds the shaft.
The shaft has removable top and
bottom jewel bearings. The shaft rides between the
bottom pin bearing and the upper pin bearing with the
cylinder rotating in an air gap formed by the electro
magnet and the magnetic core.
The bridge is secured to the electromagnet and
frame by two mounting screws. In addition to holding
the upper pin bearing, the bridge
is
used for mounting
the adjustable stationary contact housing.
The
stationary contact housing is held in position by a
spring type clamp. The spring adjuster is located on
the underside of the bridge and is attached to the
moving contact arm by a spiral spring.
The spring
adjuster is also held in place by a spring type clamp.
With the contacts closed, the electrical connec
tion is made through the stationary contact housing
clamp, to the moving contact, through the spiral
spring out to the spring adjuster clamp.
When the current in the overcurrent unit exceeds
the pick-up value the contacts open, allowing positive
potential to be applied to the carrier transmitter.
A
transformer and varistor assembly is used in
conjunction with the overcurrent unit.
The trans
former is of the sati.D'ating type which limits the
energy to the overcment unit and reduces the burden
EFFECT IVE NOVEMBER
1959
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