GE STD16C - INSTALLATION AND TESTING; INSTALLATION PROCEDURE

GEK—45307
1.
Minimum
pickup
of
main
operating
unit.
2.
Minimum
pickup
of
the
instantaneous
overcurrent
unit.
3.
A
single
check
point
on
the
harmonic
restraint
characteristic.
4.
A
single
check
point
on
the
slope
characteristic
curve,
for
the
approximate
slope
expected
to
be
used.
Test
Equipment
In
order
to facilitate
tests,
the
following
test
equipment
is
recommended:
1.
Two
load
boxes
for
regulating
the
test
currents
2.
Three
ammeters
(two
AC and
one DC)
for
measuring
the
test
currents
3.
A
test
rectifier
for
checking
the
relays
response
to
the
second
harmonic.
(See
Figure
13.)
4.
One
indicating
lamp
5.
Two
single-pole
double—throw
switch
selectors
6.
A
double-pole
single-throw
line
switch.
Check
the
pickup
of
the main
unit,
using
the
connections
shown
in
Figure
14.
During
this
test,
the selector
switches
(S2
and
S4)
are
open,
and
current
passes
through
one
restraint
winding
and
the
operate
winding
only.
For
example,
with
a
relay
set
with
a
25%
slope
and
at
the
2.9 ampere
ratio-matching
taps,
the
main
unit
should
pick
up at
30%
of
tap
rating,
1O%,
or
the
pickup
should
be between
0.78
and
0.96
amperes.
A
source
of
DC
power
at
rated
voltage
should
be
connected
as
shown
in
Figure
14;
the
indicating
lamp
will
provide
a
signal,
showing
that
the
main
unit
has
operated.
For
an
additional
pickup
test,
the
pickup
should
be
1.5
amperes,
with
current
flowing
in
terminals
5
and
6
and
the
tap plugs
in
the
5
ampere
tap
and
the
25%
slope
tap
position.
If
the
pickup
is
between
1.35
and
1.65
amperes,
no
adjustment
should
be made.
The
pickup
of
the
relay
has
wider
permissible
variations
than
most
protective
relays,
but
due
to
the
relay
design
and
application,
the
relay
accuracy
is
entirely
adequate
under
all
conditions,
even
during
transformer
magnetizing
inrush
or
severe
fault
conditions.
With
the
selector
switch,
ST,
in
the
A
position,
check
the
harmonic
current
restraint,
as
described
in
the section
on
INSTALlATION
PROCEDURE.
The
instantaneous
overcurrent
unit
should
be
checked
by passing
a
high
current
through
the
5-6
terminals.
The
pickup
should
be
about
eight
times
tap
rating.
Check
through—current
restraint,
as
described
in
the
section
on
INSTALLATION
PROCEDURE.
INSTALLATION
PROCEDURE
TESTS
Before
placing
the
relays
in
service,
check
the relay
calibration
to
be
used
in
its
final
location,
to
ensure
that
it
is correct.
The following
test
procedure
is
outlined
for
this
purpose.
18