Ampcontrol CSM Pty Ltd - ABN 35 000 770 141
ECDB006 MEC-1 User Manual
MEC-1 USER MANUAL R0 13/03/2020 13:16 Page 13 of 18
6 AS/NZS 2081 PROTECTION FUNCTION: EARTH CONTINUITY
The primary function of the MEC-1 relay is to provide Earth Continuity protection in accordance with AS/NZS 2081: 2011. This
protection ensures the integrity of the earth connection between an outlet and a load via the pilot conductor in the cable.
In a typical installation the MEC-1’s pilot terminal will be connected to the pilot conductor of a trailing or reeling cable. The load
end of the pilot conductor will then be terminated with a diode to earth, creating a return path through the earth conductors of
the cable to the main earth point of the outlet and then to the MEC-1’s earth terminals. The MEC-1 measures the resistance of
this pilot-earth loop (series resistance) and the pilot resistance to earth (shunt resistance). If the pilot-earth loop is not healthy
(series resistance greater than the selected trip value or shunt resistance lower than 1.25kΩ), a trip occurs which de-energises
the output relay within the selected trip time.
The trip can be configured as latching or non-latching. This allows the user to choose if the trip is manually or automatically
reset once the pilot - earth loop is healthy.
CAUTION!
Cable parameters are important to the correct operation of the Pilot E/C function.
Resistance & capacitance values limit the length of cable that the relay can drive.
6.1 Series Resistance
The MEC-1 relay measure the series resistance of the pilot-earth loop by applying a positive voltage to the pilot conductor and
measuring the pilot current. If the series resistance is detected to be above the user selected level, the MEC-1 de-energises its
output relay and the LEDs on the front panel will indicate an open circuit fault. The pilot-earth loop resistance will still
continuously be monitored even in the event of a trip.
• The MEC-1 cannot be re-started until the fault has been cleared.
• A power cycle will not reset the trip.
• In non-latching mode, the MEC-1 will automatically reset after the fault has been cleared.
• In latching mode, a manual reset is needed after the fault has been cleared.
• The trip level and time can be selected using the rotary switch on the front panel.
6.2 Shunt Resistance
The MEC-1 measures the shunt resistance (pilot to earth) by applying a negative voltage to the pilot conductor and measuring
the pilot current. If the shunt resistance is detected to be below 1.25kΩ, the MEC-1’s output relay will be de-energised and the
LEDs on the front panel will indicate a short circuit fault. The shunt resistance will still continuously be monitored even in the
event of a trip.
• The MEC-1 cannot be re-started until the fault has been cleared.
• A power cycle will not reset the relay.
• In non-latching mode, the relay will automatically reset after the fault has been cleared.
• In latching mode, a manual reset is needed after the fault has been cleared.
• The trip time can be selected using the rotary switch on the front panel.
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