Masterpact MTZ Circuit Protection Accessories

External Sensor for Neutral and Ground-Fault Protection (ENCT)

External Sensor for Neutral Ground-Fault Protection (TCE)

Installed on the neutral conductor, the external sensor enables the circuit breaker to perform:

  • Neutral protection for three pole devices only.

  • Neutral current measurement.

  • Ground-fault protection for three-pole circuit breakers on 4-wire systems.

For MTZ1 or MTZ2, a single sensor with a single wire is provided.

For MTZ3 both single sensor with single wire and double sensor with double wires are available.

For oversized neutral protection the sensor rating must be compatible with the measurement range: 1.6 x In (available up to MTZ2 40 for MTZ2 and MTZ1 16 for MTZ1)

External Sensor for Source-Ground Return Protection (SGR)

External Sensor for Source Ground-Return Protection


The sensor is installed around the connection of the transformer neutral point to ground and connected to the Micrologic 6.0 X control unit via a Modified Differential Ground-Fault (MDGF) module to provide the source ground-return (SGR) protection (see NHA92405).

Connection of the Secondary Circuit

Requires Masterpact devices equipped with a Micrologic 6.0 X control unit:

  • Between the external transformer and the MDGF module:

    • unshielded cable with 1 twisted pair

    • maximum length 150 meters

    • cable cross-sectional area 0.4 to 1.5 mm2 (21 to 16 AWG)

    • recommended cable: Belden™ 9409 or equivalent

  • Between the MDGF module and the Micrologic 6.0 X control unit:

    • unshielded cable

    • maximum length 10 meters

    • cable cross-sectional area 0.8 to 2.5 mm2 (18 to 14 AWG)

    • recommended cable: Belden 9409 or equivalent

    • terminals 5 and 6 may not be used at the same time:

      • use terminal 5 for MTZ2 08 to 40

      • use terminal 6 for MTZ3 40 to 63

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