Westinghouse KRD-4, Инструкция по установке, эксплуатации и обслуживанию

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DIR ECTI ONAL OVERCURRENT GROUND R E LAYS
IMOIC.HIIIb
CONTACT OR
SWI TCh -----
W I TH RELAT I V E IMSTAIITAMEOUS
POUR i fY AS SHOWN, THE
OIRECTIOIIAL U II I T COIITAC"FS CLOSE.
fRONT
VIEW
.:IHRCUII.ti.EIIT U II J T
( UPPER
urHrJ
SATUliA T i ri "
fRAHSfOib4fli
U f �ECT
I OIIAL
Ull
IT
(LUWEtl. U K i f )
183A022
Fig.
2.
lnternol Schematic ol the Type KRC Relay in the
FT3 l Case.
tional unit should pick up for a fault , this short-cir­
cuit is removed, allowing the overcurrent contact to
commence closing almost simultaneously with the
directional contact for high speed operation.
O vercurrent U n i t T ra n s fo rmer
Thi s transformer is of the saturating type for
limitin g the energy to the overcurrent unit at higher
values of fault current and to reduce C.T. burden. Tbe
primary winding is tapped and these tap s are brought
out to a tap block for ease in changing the pick-up
of the overcurrent unit.
The use of a tapped trans­
former provides approximately the same energy level
at
a given multiple of pickup current for any tap set­
ting, resulting in one time curve throughout the range
of the relay.
Across the secondary is connected a non-linear
resistor known as a varistor. The effect of the var­
istor is to reduce the voltage peaks applied to the
overcurrent unit and phase shifting c apacitor.
I N D I CA T I NG C O N T A C T O R S W I T C H U N I T ( I C S )
The indicating contactor switch i s a small d-e
operated clapper type device. A magnetic armature,
to which leaf-spring mounted contacts are attached,
is attracted to the magnetic core upon ener gi zation of
the switch. When the switch closes, the moving
contacts bridge two stationary contacts, completing
the trip circuit. Also during this operation two fingers
on the armature deflect a spring located on the front
of the switch , which allows the operation indicator
target to drop . The target is reset from the outside of
the case by a push rod located at the bottom of the
IIID ICATII'I_.
COtiTACTOR
SWITCh -
--
W I T h ULHI�E IIISTAIITAtlOUS
POLA R i n AS SuOW�. THE
� I RECTI OIIAL I.!N I T COPITACTS
CliJSL
FRONT
VIEW
O�UWRREIIT U I U T
( UPPER U N I T )
--SAT;JRATIMG
-
TRAMSFO�ER
?""D I RECTIONAL U II I f
( LOWER U N I T )
CHASSIS OPERATED
_ SHORT/Nil SWITCH
183A025
Fig. 3. Internal Schematic
of
the Type KRP Relay in the
FT3 l Case.
cover.
The front spring, in addition to holding the target,
provides restraint for the armature and thus controls
the pickup value of the switch .
C H A R A C T E R I S T I C S
The relays are available in the following current
ranges :
R a n g e T a p s
0.5-2 Amps 0 . 5 0. 75 1 . 0 1 . 25 1 .5 2
1-4 1 . 0 1 .5 2 . 0
2.5
3 . 0 4 .0
2-8 2
3 4 5
6
8
4-1 6 4
6 8 9 1 2 1 6
1Q-40 10 15 20
24
30 40
The tap value is the minimum current required to
j ust close the overcurrent relay contacts. For pick­
up settings in between taps refer to the section under
adjustments.
T y pe K R P R e l ay
The KRP relay is designed for potential polari­
zation and has its maximum torque when the current
lags the voltage by approximately 60 degrees. The
shifting of the maximum torque angle is accomplished
by the use of an internally mounted phase shifter as
shown in the internal schematic .
The directional unit minimum pick-up is approxi­
mately 1 volt and 2 amperes at its maximum torque
angle for the 0 .5 to 2, 1 to 4, and 2 to 8 ampere
range relays. For the 4 to 16 and 10 to 40 ampere
3
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