8 VOLTAGE RELATED FUNCTIONS
8.1 Main Contactor Fail Protection
The Main Contactor Fail (MCF) protection operates if the Main Contactor fails to function by:
a. Failing to open when required. This is achieved by comparing the state of the main contactor (via
the Main Contactor Input MCI) against the state of the MCR Relay output. This provides a “Pilot
Fail Timer” function.
b. Failing to maintain insulation across the contacts when the contactor is open. The Cable
Connection Module is used to measure the voltage on the load side of the contactor. If this
exceeds 10% of the rated line voltage, a trip will occur.
This function is inhibited immediately after the main contactor opens or a cable test is performed to allow
for the cable capacitance to discharge.
The back EMF inhibit time is adjustable from 2 to 40 seconds (See Section 9, User Adjustable Settings).
A main contactor fail trip causes the CBR Relay to de-energise, which trips the circuit breaker. An
internal battery backed indication flag in the HPB Relay is also tripped. An LED on the front panel of the
HPB Relay begins to flash.
The “MCF” LED on the Remote Display Module flashes and the open collector output on the HPB is
switched on to provide remote monitoring if required.
To reset the flag, access to the relay is necessary. The reset button is accessible through the front fascia
of the relay and must be pressed for 1 second.
8.2 Under Voltage Trip
Under voltage protection is enabled as soon as the main contactor is closed (indicated by closing the
MCI input). If any of the phase voltages drop below the selected trip setting of the nominal line voltage
for 800ms then the outlet is stopped. This is recorded in the event long as “uVOLT Trip”.
The trip level is selectable from 30% to 80% in 10% increments or can be set to “Off” (level 8, position 6)
on the HDM Remote Display Module.
The “Off” selection disables the under voltage trip function and is usually used for non 6.6kV
installations.
8.3 Voltage Metering
The Cable Connection Module (CCMB), in addition to enabling the Earth Fault test, is used to provide
line voltage metering.
The outgoing line voltages for each of the 3 phases are displayed as a % of the nominal line voltage on
the HDM Remote Display module (level 4, position 1). The maximum reading is 140% for the 6.6kV
systems and 120% for the 11kV and 22kV systems.
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