Count Reset
The count reset feature resets the sectionalizer count to
zero whenever current below the actuating level flows
through the sectionalizer for longer than the pro-
grammed reset time without interruption. The reset time
settings have a tolerance of ±10 percent.
It can be verified by interrupting an overcurrent flow
through the sectionalizer one time less than the counts-
to-open setting, then allowing load current to flow for
periods just under and just over the reset setting. The
sectionalizer should open if the overcurrent for the final
count is interrupted within the reset time period (count
has reset to zero). The following procedures may be
used to verify the count reset:
1.
Jumper the ground actuating current resistor with a
short lead to disable the ground-sensing circuit.
2.
Program the sectionalizer control for two counts-to-
open and set the COUNT RESET SELECTOR to 15
seconds.
3.
Jumper terminals P and D together.
4.
Close the sectionalizer.
5.
With test circuit connected to phase A of the section-
alizer and S1 open, close S2 and raise the test cur-
rent to slightly above the appropriate value shown in
Column B of Table 8. Hold S2 closed for at least
three seconds.
6.
Release S2 to simulate a backup protective device
clearing the overcurrent. The sectionalizer will regis-
ter a count.
7.
Close S1 for 13.5 seconds.
8.
Momentarily close and then release switch S2. The
sectionalizer
should
open, verifying that the count
reset has not been activated.
9.
Reclose the sectionalizer and then close and release
S2 once to register one overcurrent interruption
count.
10.
Close S1 for slightly more than 16.5 seconds.
11.
Momentarily close and release switch S2. The sec-
tionalizer
should not
open, verifying that the count
reset has been activated and the first count has
been erased.
12.
Again, close and release S2. The sectionalizer
should
open.
13.
Remove the jumper form terminals P and D.
Inrush-Current Restraint
The inrush-current restraint feature distinguishes
between fault currents and inrush currents. For fault cur-
rent interruptions, the sectionalizer counts and opens
normally. For an inrush-current condition, the phase and
ground minimum actuating current detection is blocked
for three seconds to prevent counting the inrush current.
The three-second time interval allows for system inrush
parameters to stabilize prior to allowing the sensitivity of
the sectionalizer to return to its programmed state.
The operation of the inrush-current restraint can be veri-
fied by simulating a fault condition (the overcurrent is
preceded by an overcurrent interruption) and an inrush
condition (the overcurrent is preceded by a load current
interruption).
The following procedure can be used to verify the
inrush-current restraint feature.
1.
Jumper the ground actuating current resistor with a
short lead to disable the ground sensing circuit.
2.
Set the COUNTS TO OPEN SELECTOR switch to
1
.
3.
Manually close the sectionalizer.
4.
With the test circuit connected to phase A of the sec-
tionalizer and S1 open, hold S2 closed and raise the
test current to slightly below the appropriate value
shown in Column A of Table 8.
5.
Release S2 to simulate a backup opening with only
load current flowing through the sectionalizer when
current was interrupted. The sectionalizer
should
not
open.
6.
Close S2 and in
no more than three seconds
adjust the test current to just below twice the appro-
priate value shown in Column A of Table 8 to simu-
late an inrush condition. Release S2. The sectional-
izer
should not
open, verifying that the inrush
restraint feature has been activated.
7.
Reset the inrush restraint as follows:
A.
Short test terminals D and P together.
B.
Close S1 closed for 3.5 seconds.
C.
Open S1 and remove short from Test Terminals D
and P.
8.
Close S2 and raise the test current to slightly above
the appropriate value shown in Column B of Table 8.
9.
Release S2 to simulate a backup opening with fault
current flowing through the sectionalizer when cur-
rent was interrupted. The sectionalizer
should
open.
10.
Close the sectionalizer.
11.
Repeat step 9 to simulate a fault condition.
12.
Release S2. The sectionalizer should open verifying
that the inrush restraint has not been activated.
Post-Test Procedures
After testing has been completed, make sure that the
control settings are programmed to the operating param-
eters as originally specified.
19
S270-20-3
!
SAFETY
FOR LIFE
