6 PRODUCT OPERATION
6.1 Outlet Control
In a typical installation, the outlet contactor is directly controlled by the Protection Element. The
supervising PLC will send commands to the Protection Element to start or stop the outlet. The Protection
Element will respond by controlling its MCR output accordingly. In the event of any trip condition
occurring, the Protection Element will open the MCR output (or CBR output as appropriate) and prevent
reclosing the output until the fault condition has cleared and the trip has been reset.
To close an outlet controlled by a Protection Element, the supervising PLC will send a start command.
The following start sequence will be followed:
If there are any active trips, the Protection Element will ignore any start command received.
If all trips are cleared, the Protection Element will initiate a start sequence.
An earth fault lockout test is conducted. This test checks for a cable fault to earth. The test
voltage and current are limited to intrinsically safe levels. If the test fails, the start sequence will
be cancelled and the Protection Element will report an earth fault lockout trip.
If the earth fault lockout test passes, the Protection Element may then conduct an optional high
voltage DC insulation test on the cable. If the insulation test fails, the start sequence will be
cancelled and the Protection Element will report an insulation test trip. The insulation test can
also be disabled via parameter settings.
If the insulation test passes, the start sequence moves to the closing state and the MCR output
will be closed.
The Protection Element now waits for the MCI digital input to close. This auxiliary feedback from
the signal confirms that the main contactor has closed. If the MCI does not follow the MCR within
five seconds a ‘close fail’ trip will occur and the start sequence will be cancelled.
If the MCI digital input closes, the Protection Element moves from the start sequence to the
running state. It will continue in the running state with the outlet closed until a stop command is
received or any protection function trips.
If at any point during the start sequence a stop command is received or a protection function trips
the start sequence is immediately cancelled and the MCR (or CBR if appropriate) output will be
opened.
6.2 Control of Resets
All trip resets in the Protection Element are handled by positive edge reset signal events. In this way,
continually driven reset signals will not reset faults. Most trips are reset with a general reset. Some trips
have a dedicated reset, to allow selective control of the reset functions and to provide a level of authority
associated with resetting faults. The trips that require additional reset commands include the Earth
Leakage, Thermal Memory for motor overload protection, Short Circuit and MCF Reset.
Main Contactor Failure events generate a trip that can be reset by the PLC. These trips require an
inspection of the switching equipment associated with the outlet controlling Protection Element and as
such a reset push-button is accessible from the front of the Protection Element and can be operated with
power off.
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