GE GCX51A - Construction

GEI
-
98328
The
percent tap
setting
required
to
obtain
this
reach
is obtained
from the
same
equation
that
was
used
for the
first
zone
.
Since
the
same
unit is
used
for second
-
zone
as
is
used for
first
zone
,
the
same
base
reach
tap
setting
is
common
to
both
zones
.
Thus
,
for the second
-
zone
0.50
x
100
=
33
%
T
=
1.50
To
achieve
this
setting
,
the lower
No
.
2
tap
lead
would
be connected
to
the
30
%
point
,
and
the
upper
No
.
2
tap
lead
would
be connected
to
the
3
%
point
.
The
tap
setting
for
the
third
-
zone
MHO
unit is
given
by
the
following
equation
:
T
=
Zmin
x
100
cos
(
60
-
0
)
ZL
where
:
Third
zone
(
E
2
)
tap
setting
in
percent
.
Minimum
reach of the
MHO
unit
as
marked
on
the
nameplate
,
standard
reach
relay
,
this is
2.5
ohms
.
Desired
impedance
reach
in
secondary
phase
-
to
-
neutral ohms
.
Impedance
of
angle
of
Z
|
_
Angle
of
maximum
torque
of the
MHO
unit
.
T
For
the
Zmin
-
ZL
0
60
°
Assume
that
in
this
case
it
is
desired
to set
the
third
zone
to
reach
2.75
80
°
secondary
phase
-
to
-
neutral
ohms
.
The
percent
tap
setting
for
such
a
reach
is
:
2.5
x
100
cos
(
60
-
80
)
=
85.5
%
Set
the
thircTzone
(
E
?
)
taps
for
86
%
.
Note
that
the
restraint
tap
setting
of the
MHO
unit
must
not
be
set
for
less
than
25
%
.
Also refer
to
Appendix
I
for
possible
further
limitations
on
the
MHO
unit
reach
setting
.
The
instantaneous
unit
setting
should
be
no
lower than
115
%
of
full
-
load
current
.
In
this
case
,
with
600
/
5
CT
'
s
and
a
maximum
load
current
of
450
amperes
,
the
instantaneous
overcurrent
unit
must
be
set to
pick
up
above
:
T
=
2.75
450
x
5
*
1.15
=
4.3
amperes
It
should
be
noted
that
with
such
a
setting
the
GCX
relays
will
not
operate
for
any
faults
that
do
not
produce
at
least
4.3
amperes
.
600
CONSTRUCTION
The
Type
GCX
51
relays
are
assembled
in
the
standard
large
-
size
,
double
-
end
(
L
2
)
drawout
case
,
having
studs
at
both ends
in
the
rear
for
external
connections
.
The
electrical
connections
between
the
relay
units
and the
case
studs
are
made
through
stationary
molded
inner
and
outer
blocks
,
between
which
nests
a
removable
connecting
plug
that
completes
the
circuits
.
The
outer
blocks
attached
to
the
case
have
the
studs
for the
external
connections
,
and
the
inner
blocks
have
the
terminals
for
the
internal
connections
.
14
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