GE GCX51A - Contact Cleaning; Servicing; Control - Spring Adjustment; Mho Unit

GE
1
-
98328
is
away
from
the
bus
and
into
the
protected
line
section
,
the
MHO
unit
should
operate
.
phase
angle
may
be
such
that
the
MHO
unit
will
not
operate
.
If
the
reactive
power
flow
is into
the
station
bus
,
the
resulting
PERIODIC
CHECKS
AND
ROUTINE
MAINTENANCE
In
view
of
the
vital
role of
protective
relays
in
the
operation
of
a
power
system
,
it is
important
that
a
periodic
test
program
be followed
.
It
is
recognized
that
the
interval
between
periodic
checks
will
vary
depending
upon
environment
,
type
of
relay
,
and the
user
'
s
experience
with
periodic
testing
,
accumulated
enough
experience
to
select
the
test
interval
best
suited
to
his
individual
requirements
it is
suggested
that the
points
listed
under
INSTALLATION
PROCEDURE
be checked
at
an
interval
of
from
one
to two
years
.
Until
the
user
has
Contact
Cleaning
For
cleaning
fine
silver
contacts
,
a
flexible
burnishing
tool
should
be
used
.
This
consists
of
a
flexible
strip
of
metal
with
an
etch
-
roughened
surface
resembling
in
effect
a
superfine
file
.
The
polishing
action
is
so
delicate
that
no
scratches
are
left
,
yet
it
will
clean
off
any
corrosion
thoroughly
and
rapidly
,
flexibility
ensures
the
cleaning
of
the
actual
points
of
contact
,
knives
,
files
,
abrasive
paper
or
cloth
of
any
kind
to
clean
relay
contacts
.
Its
Do
not
use
SERVICING
If
it
is
found
during
the
installation
or
periodic
tests
that the
OHM
or
MHO
unit
calibrations
are
out
of
limits
,
they
should
be
recalibrated
as
outlined
in
the
following
paragraphs
,
laboratory
.
The
circuit
components
listed
below
,
which
are
normally
considered
as
factory adjustments
,
are
used
in
recalibrating
the
units
,
located from
Figures
1
and
2
.
It
is
suggested
that these
calibrations
be made
in
the
These
parts
may
be
R
3
-
MHO
unit
reach
adjustment
.
R
4
-
MHO
unit
phase
-
angle
adjustment
.
Rl
-
OHM
unit
reach
adjustment
.
R
2
-
OHM
unit
phase
-
angle
adjustment
.
Before
making
pickup
or
phase
-
angle
adjustments
on
the
MHO
or
OHM
units
,
the
unit
should be
allowed
to
heat
up
for
approximately
15
minutes
,
energized
with
voltage
alone
.
Also
it is
important
that
the
relay
be
mounted
in
upright
position
so
that
the units
are
level
.
NOTE
:
MHO
UNIT
a
.
Control
-
Spring Adjustment
Connect
the
relay
as
shown
in
Figure
10
and
set
the
E
2
tap
leads
at
100
%
.
Make
sure
that
the
relay
is
level
in
its
upright
position
.
With
the
current
set at
5
amperes
and the
voltage
across
studs
17
-
18
at
120
volts
,
set
the
phase
shifter
so
that
the
phase
-
angle
meter
reads
300
°
(
i
.
e
.
,
current
lags
voltage
by
60
°
)
.
26
Courtesy of NationalSwitchgear.com