GE GCX51A - Ohmic Reach; Torque Check

GEI
-
98328
With the
current set
at
5
amperes
and
the
voltage
across
studs
17
-
18
oat
120
volts
,
set
the
phase
shifter
so
that the
phase
-
angle
meter
reads
300
°
(
i
.
e
.
current
lags
the
voltage
on
studs
17
-
18
by
60
°
)
.
Now reduce
the
voltage
to
2
volts and the
current
to
about
2
amperes
.
Gradually
increase
the
current
until
the
MHO
unit
contacts
just
close
.
This should
occur
between
4.1
-
4.9
amperes
for
the
2.5
Q
mho
,
and
5.1
-
5.9
amperes
for
the
1.0
Q
mho
.
b
.
Ohmic
Reach
With
the
relay
still connected
as
shown
in
Figure
10
and the
E
2
taps
in
the
100
%
position
,
set
the
voltage
at
the value shown
in
Table
XI
for
the
relay
to
be checked
.
Increase the
current
until
the
MHO
unit
contacts
just
close
.
This
should
occur
within
the
limits
shown
in
Table
XI
:
TABLE XI
Equiv
.
Test
Reach
(
0
-
0
Ohms
)
Pickup
Basic
Min
.
Reach
(
0
-
N
Ohms
)
V
17
-
18
Set
At
Relay
Amps
19.4
-
20.6
7
40
V
Short
Reach
T
14.6
-
15.4
Standard
Reach
275
5
75
V
Note
that
for
the
test
conditions
the
MHO
unit
sees
a
phase
-
to
-
phase
fault
of
twice the basic
minimum reach
.
c
.
Anqle
-
of
-
Maximum
-
Torque
Check
For
the
angle
-
of
-
maximum
-
torque
check
,
the
connections
of
Figure
10
will
still
be used
with
the
E
2
taps
still
at
100
%
,
and the
voltage
set
at
the value
shown
in
Table
XI
for
the
relay
to
be
checked
.
The
pickup
should
then be
checked
with the
current
displaced
30
°
from
the
maximum
torque
position
in
both
the
lead
and
lag
direction
.
Set
the
phase
shifter
so
that
the
phase
-
angle
meter
reads
330
°
.
Note
that
while
the
phase
angle
is
being
set
the
current
should
be
at
5
amperes
and
the
voltage
on
studs
17
-
18
should be
increased
temporarily
to
120
volts
.
With
voltage
again
at
the
value shown
in
Table
XI
,
increase the
current
slowly
until
the
MHO
unit
picks
up
.
The
pickup
current
should
be
22
to
24
amperes
for
the
short
-
reach
relay
and
16.5
to
18.2
amperes
for
the
standard
-
reach
relay
.
Now
reset
the
phase
angle
at
270
°
and
again
check
the
current
required
to
pick
up
the
MHO
unit
.
The
pickup
current
should
fall
within
the
same
limits
given
in
the
previous
paragraph
.
Note that the
two
angles
used
in
the
previous
check
,
i
.
e
.
,
330
°
and
270
°
,
are
read
30
°
away
from
the
angle
of
maximum
torque
.
An
examination
of
the
MHO
unit
impedance
characteristic
in
Figure
5
shows that the
ohmic
reach
of
the
unit
should be the
same
at
both
330
°
and
270
°
and
should
be
0.866
times
the
reach
at
the
angle
of
maximum
torque
.
17
Courtesy of NationalSwitchgear.com