Inrush-Current Restraint
The inrush-current restraint feature distinguishes
between fault currents and inrush currents. For fault
current interruptions, the sectionalizer counts and
opens normally. For an inrush-current condition, the
phase and ground minimum actuating current detec-
tion is blocked for 3 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 pro-
grammed state.
The operation of the inrush-current restraint can be
verified by simulating a fault condition (the overcur-
rent is preceded by an overcurrent interruption) and
an inrush condition (the overcurrent is preceded by a
load current interruption).
The following procedure is 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. Close the sectionalizer by operating the Manual
Control Switch to “CLOSE”.
4. With the test circuit connected to phase A of the
sectionalizer and S1 open, hold S2 closed and
raise the test current to slightly below the appro-
priate value shown in Column A of Table 9.
5. Release S2 to simulate a backup opening with
only load current flowing through the sectionaliz-
er when current was interrupted. The sectionaliz-
er should not open.
6. Close S2 and, in no more than three seconds,
adjust the test current to just below twice the
appropriate value shown in Column A of Table 9
to simulate an inrush condition. Release S2. The
sectionalizer 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 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 9.
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 by operating the Manual
Control Switch to “Close”.
11. Repeat step 9 to simulate a fault condition.
12. Release S2. The sectionalizer should open verify-
ing 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.
Reconnect X-3 and X-4 leads to battery charger board
terminals 3 and 4 respectively.
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S270-21-1