Westinghouse KRD-4, Installation, Operation, & Maintenance Instruction

Page: 63 / 114

TY P E K RV R ELAY
2D
1 0 0
90
(/)
8 0
0
z
70
0
0
liJ
6 0
(/)
...J
...J
50
:e
z
4 0
liJ
30
::E
20
1 0
0
S C A L E
1
-
0
S C A L E 2 - 0
S C A L E
3
-
0
1 0
2 0
4 0
20
40
80
T Y P I C A L T I M E C U R V ES
D I R EC T I O N A L U N I T
F O R C U R R E NT A P P L I E D I N
P H A S E W I T H VO LTAG E
� 5
v.
;/ 2 5
V.
- 1 1 0
v.
3 0
4 0 5 0
6 0
6 0 8 0 100
1 20
1 2 0
1
6 0 20 0
AMP E R E S
S CA L E
1
F O R 0.5
- 2.0
A
M
P
S A N D
2 - 8
A M P S R E L A Y
S C A L E 2 F O R 4 - 1 6 A M P S R E L AY
SCA L E
3
F O R 1 0 - 4 0
AM P S
A N D 2 0
·-
80
A M PS
R E L A Y
187Al83
Fig.
5.
Typical Time Curves of the Directional Unit.
C h e c k
The following check i s reco m m ended to insure
that the relay is in p roper working order;
Instantan eou s O v e rcurrent Unit (I)
1 . Co ntact Gap - The gap betw een the station­
ary and moving contacts with the relay in the de­
en ergized po sition s hould be approxi mat ely . 0 20 " .
2 . Minimum Trip Curre nt - The D contacts s hould
be blocked closed when checking the pick-up of the
overcurrent unit.
The pick-up o f the o vercurrent unit can b e che ck­
ed by inserting the tap screw in the desired tap ho le
and applying rated tap value current. The contact
should clo s e within ±5% of tap value current.
Directional U nit (D)
1. Cont act Gap - The gap betw een the station­
ary contact and moving contact with the relay in the
de-energiz ed po sition should be appro ximately . 0 20 " .
2. Sen sitivity - The directional unit s hould
pi ck up at its m aximum torque angle ( cu rrent l eading
the voltage by 30°) when energized with th e valu e of
current and voltage shown in Table 1 .
3 .
Spurious Torqu e Adjustm ents - Th ere should
be no spurious closing torqu e s when the operating
circuits are energized p er Table 2 with the polarizing
circuit short circuited.
I n d i c a t i n g C o n t a ctor S w i t c h ( I C S )
Close t h e m ain relay contacts and pass suffi­
cient d- e current through the trip circuit to clos e the
cont acts o f the ICS. Thi s valu e o f current s hould b e
b etween 1 and 1 . 2 amp eres. The indi cator target
should drop freely .
The contact gap s hould be approximately 5/64"
betw een the bridging m oving contact and the adj u st­
abl e s tationary contacts . The bridging movi ng con­
tact s hould touch both stationar-y contacts simultan­
eously. The third moving contact should make at
app roximately the same time.
7
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