GE STD16C - PICKUP AND OPERATING TIME

GEK—45
307
TABLE
II
TARGET
AND
SEAL-IN
UNIT
2.0
Amp
Tap
0.6
Amp
Tap
0.2
Amp
Tap
DC
Resistance
0.13
Ohms
0.6
Ohms
7
ohms
Carry
Continuously
0.5
Amps
1.5
Amps
0.25
Amps
Carry
30
Amps
for
Secs.
0.5
Secs.
Carry
10
Amps
for
30
Secs
4
Secs.
0.2
Secs.
AUXILIARY
RELAY
CONTROL
CIRCUIT
The
STD15C
and
STD16C
relays
are
available for
use
with
4S,
125,
and
250
DC
or
48,
110
and
220
DC
control
voltage,
depending
upon
the
relay
model.
A
plate
with
small
links
located
on the
front
of
the
relay
enables
the
selection
of
one
of
these
voltages.
The
STD
relay
is
provided
with
two
open
contacts connected
to
a
common
output
circuit.
The
current—closing
rating
of
the
contact
is
30
amps
for
voltages
not
exceeding
250
volts. If
more
than
one
circuit
breaker
is
to be
tripped,
or
if
the
tripping
current
exceeds
30
amperes,
an auxiliary
relay
must
be
used
with
the
STD
relay.
After
the
breaker
trips, it
is
necessary
that
the
tripping
circuit
of
these
relays
(STD
and
auxiliary)
be
de-energized
by
an
auxiliary
switch
on
the
circuit
breaker
or by
other
automatic
provisions.
A manual
reset
relay
is
recommended and
normally
used.
CHARACTERISTI
Cs
PICKUP
AND OPERATING
TIME
The
operating
characteristic
is
shown
in
Figure
7.
The
curve
for
various
percentage
slopes
shows
the
percent
slope
versus
the
throughcurrent
flowing
in
the
transformer.
The
percentage
slope
is
a
figure
given
to
a particular
slope
tap
setting,
and
indicates
an
approximate
slope
characteristic.
Pickup
at
zero
restraint
is
approximately
30%
of
tap
value
(see
Table
III).
The
dropout time,
when
the
operating
current
is reduced
to
zero
from
any
value
above
pickup,
is
less
than
25
milliseconds.
Curves
of the
operating
time
of
the
main
unit
and
of
the
instantaneous
unit
are
shown
in
Figure
5,
plotted
against
differential
current.
The
main
unit
operating
time
includes
auxiliary
unit
operating
time.
OVERCURRENT
UNIT
PICKUP
The
overcurrent
unit
is
adjusted
to pick
up
when
the
differential
current
transformer
ampere-turns
are
8
times
the
ampere
turns
produced
by
rated
tap
current
flowing
in
that
tap.
For
example:
When
only
one
CT
supplies
current,
and
the
tap
plug
for
the
CT
is
in
the
5
ampere
tap,
40
amperes
are
required
for
pickup.
This
pickup
value
is based
on
the
AC
component
of
current
transformer
output
only,
since
the
differential
current
transformer
in
the
relay
produces
only
a
half
cycle
of
any
DC
(offset)
component
present.
11