ABB KA-4 Instruction Leaflet
41-923.4M
Figure 1. Type KA-4 Relay without case. (Front View)
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41-923.4M
Sub 3
629A389
Figure 2.Internal Schematic of the Type KA-4 Relay for KR
Carrier Set.
Sub 9
629A476
Figure 3. Inter nal Schema tic of the Type KA-4 Re lay for TC
Carrier Set.
Sub 1
3491A17
Figure 4.Internal Schematic of the Type KA-4 Relay with
Modified Carrier Stop to Terminal 11 for TC Carrier
Set.
Sub 1
349A16
Figure 5.Internal Schematic of the Type KA-4 Relay for the
TA-3 tones.
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41-923.4M
shaft. The shaft has remo va ble top and botto m 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 electromagnet
and the magnetic core.
The bridge is secured to the electromagnet and
frame by two mounti ng sc rews . In a ddi tio n t o h old in g
the upper pin bear ing, 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 adjuste r 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 el ectrical 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 uni t exceeds the
pick-up value the contacts open, allowing positive
potential to be applied to the carrier transmitter.
A transformer and cu rrent limiting reactor is used i n
conjunction with the cylinder unit. The transformer
supplies one set of coils on the cylinder unit with voltage shifted by approximately 90° from the residual
current supplied directly to another set of coils. The
transformer and reactor are of the saturating type
which limits energy to the cylinder unit and reduces
the burden on the transmission line CT.
2.2. AUXILIARY UNITS
These are two solenoid- type cont actor switches designated as CSP and CSG. The plunger of the contactor switch has a circular conduc ting disc mou nted on
its lower end and as the pl unger travels upwar d, the
disc bridges three silver stationary contacts. The
CSP switch is ener gized by the operati on of t he sec ond zone or KD-10 distance relay, and the CSG
switch, by the operation of the directi onal and overcurrent units of the KRD-4 ground relay. The contacts
of the two switches are connected in parallel as
shown in the internal schematic. The operation of
either of these switches conn ects the carrier control
circuit to negative to stop carrier, and energizes the
RRT operating coil of the receiver relay unit.
Figure 6.Typical Time Characteristics of c arrier start over-
current unit of the type KA-4 Relay.
2.3. RECEIVER UNIT
The receiver unit consists of an armature and contacts mounted on a leaf spring supporte d symmetrically within a magnet frame. The armature rides in
the front air-gap of the fr ame with the contacts projecting outside. The poles of a permanent magnet
clamp directly to each side of the frame. Two adjustable shunts are located across the rear air-gaps.
These change the reluctance of the magnetic path as
shown in Figure 7 so as to force some of the flux thru
the moving armature which is fastened to the fram e
midway between the two rear air gaps. Flux in the
armature polarizes it and creates a magnetic bias,
causing it to move towards either the left or right,
depending upon the adjustment.
Tw o st ati ona ry c onta ct sc re ws ar e m ount ed t o t he l eft
(front view) of the moving contact assembly and
adjusted for normally open contac ts. These co ntacts
are designated, RRP and RRG, and are connected in
the phase and ground trip circuit respecti vely. These
contacts are operate d by two concentric coils, RRT
and RRH, which are placed around the armature and
within the magnetic fra me. RRT is the operating coil
and receives its en ergy from the local battery when
either CSP or CSG is clo se d. R R H is th e h o ld ing c oil
and receives its en ergy from the carrier transmitted
either from the local tra nsmi tter or th e o ne a t th e en d
of the line section. These two coils are connect ed in
oppose each other with the operating coil, RRT oper-
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Shunt
41-923.4M
N
S
N
BALANCED AIR GAPS UNBALANCED AIR GAPS
S
Moving Contact
Figure 7. Permanent Magnet Flux Paths of Receiver and Alarm Units
Permanent
Magnet
Armature
ating to close the RRP and RRG contacts and trip;
and the holding co il, R RH to h old t he RRP and RRG
contacts open and block tripping. The restraining
torque of the RRH coil is sufficient to overcome th e
operating torque of the RRT coil. Consequently, RRP
and RRG contacts cannot c lose as long as RRH is
energized.
2.4. ALARM UNIT
The alarm unit is similar in construction to the
receiver unit except that it is energized by a single
coil and opera tes a singl e set of c ontac ts. T he c oil is
energized by the received carrier to close its contacts
and give an alarm. This unit has a higher pick-up
than that of the receiver unit in order to obtain a
direct check on the sensi tivity of the car rier transmitter-receiver. The failure of the alarm unit to pick-up
when carrier is started indicates insufficient output
from the transmitter receivers.
2.5. SQUELCH UNIT
The function of the squelch unit is to hold of the carrier for a period o f 15 0 m il lise co nds af ter th e B r eaker
“a” contact opens. This is to insure that all other ter minals of the line are tripp ed before allowing carrier
to be transmitted for any functions.
The squelch unit is a telephone type unit of slow
release type.
N
S
N
S
N
Additional
Flux Path
183A062
In these relays, an electromagnet attracts a right
angle iron bracket which in turn operates one normally open contact. The sl ow release is obtained by
a copper slug locat ed at the end opposite from the
armature. When the coil beco mes deenergized, the
change in flux through the slug results in an e lectromotive force and associated current in it. This current
produces a flux whic h aids the main flux and d elays
the release of the arm ature. When the coil is energized, the operation of the relay is not appreciably
delayed because the armature is operated by flux not
linking the slug.
2.6. OPERATION INDICATOR
The operation indicator gives a visual indication of a
carrier tripping op eration for phase faul ts by the distance relay through the RRP contac ts. For a groun d
fault carrier relaying ope ration, the indi cating conta ctor switch (ICS) located in the ground relay will drop a
target.
3.0 CHARACTERISTICS
The characteristics of the various elements of the
relays are as follows:
The pick-up and o perating values of thes e units are
given under “Adjustments and Maintenance”.
The time characteristic of the overcurrent unit is
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