GE GCX51A - Operating Principles; MHO Unit; OHM Unit

GEI
-
98328
OPERATING
PRINCIPLES
MHO
Unit
The
MHO
unit
of
the
Type
GCX
51
relays
is
of the
four
-
pole
induction
cylinder
construction
(
see
Figure
14
)
with
schematic
connections
as
shown
in
Figure
4
.
The
two
side
poles
,
energized
with
phase
-
to
-
phase
voltage
,
produce
the
polarizing
flux
.
The flux
in
the
front
pole
,
energized
with
a
percentage
of the
same
phase
-
to
-
phase
voltage
,
interacts with
the
polarizing
flux
to
produce
restraint
torque
.
The
flux
in
the
rear
pole
,
energized
with
the
two
line
currents
associated
with
the
same
phase
-
to
-
phase
voltage
,
interacts
with
the
polarizing
flux
to
produce
the
operating
torque
.
The
torque
at
the
balance
point
can
therefore
be
expressed
by
the
following
equation
:
T
=
0
=
El
cos
(
0
-
0
)
-
KE
2
where
:
E
=
The
phase
-
to
-
phase voltage
(
E
12
)
I
=
The
delta
current
(
Ii
-
I
2
)
0
=
Angle
of
maximum
torque
of
the
unit
0
=
Power
factor
angle
of
fault
impedance
K
=
Design
constant
Dividing
through
by
E
2
and
transposing
,
the
equation
reduces
to
the
following
expression
in
terms
of
impedance
:
1
Y
cos
(
0
-
0
)
=
K
cos
(
0
-
0
)
=
K
Thus the
unit
will
pick
up
at
a
constant
component
of
admittance
at
a
fixed
angle
,
depending
on
the
angle
of
maximum
torque
.
Hence
the
name
MHO
unit
.
or
Z
OHM
Unit
The
OHM
unit
of the
GCX
51
relays
is
also of
the four
-
pole
induction
cylinder
construction
(
see
Figure
14
)
with
schematic
connections
as
shown
in
Figure
4
.
front and
back
poles
,
energized
with
delta
current
,
produce
the
polarizing
flux
.
The
side
poles
are
energized
with
a
voltage
equal
to
the
difference
between
the
operating
quantity
,
IZT
and the
restraint
voltage
,
E
,
where
I
is
the
delta
current
and
ZT
is
the
transfer
impedance
of
the
transactor
.
Torque
on
the
unit
results
from
interaction
between
the
net
flux
in
the
side
and the
polarizing
flux
in
the
front
and
rear
poles
,
and
at
the
balance
point
can
be
expressed
by
the
following
equation
:
T
=
0
=
Kl
(
IZT
-
E
)
sin
p
The
where
:
E
=
phase
-
to
-
phase voltage
(
E
^
)
I
=
delta
current
(
Ii
-
I
2
)
Zj
=
transfer
impedance
of
transactor
(
design
constant
)
p
=
angle
between
I
and
(
IZj
-
E
)
K
=
design
constant
6
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