Additional Micrologic X Control Unit Functions

Neutral Overload Protection on Four-Pole Circuit Breakers

A four-pole circuit breaker neutral protection is set remotely:

  • Neutral protection set at unprotected.

  • Neutral protection set at 0.5 x Ir.

  • Neutral protection set at Ir.
    Neutral protection is greater than Ir, but lower than In and limited at 1.6 Ir phase.

For a three-pole circuit breaker used in a 4-wire circuit, the protection of the neutral requires an additional external neutral CT (ENCT). A long-time overcurrent characteristic is dedicated to the neutral protection.

Trip Coil Supervision (ANSI 74)

The Micrologic X control unit continuously monitors the electrical continuity of the circuit breaker tripping coil. It generates an alarm if a problem is detected.

Lock-Out Function (ANSI 86)

If the circuit breaker is tripped from an overcurrent event or from one of the protective functions the circuit breaker is locked in the open position until it is reset manually or electrically. Masterpact MTZ circuit breakers are also equipped with an interlocking function (see Masterpact MTZ Locking and Interlocking Accessories).

Dual Settings

The Micrologic X control unit is equipped with dual protection settings which allow the user to have a second set of protection settings. This allows users to easily switch between settings.

A typical application is to adjust the short-circuit protection when an installation can be supplied by two sources (grid / generator set) with different levels of available short-circuit current. The settings can be selected by one of the following means:

  • MTZ App

  • by a digital input through the IO module

  • via Ethernet

  • from the embedded HMI

Overcurrent and Trip Cause Indications

Five LEDs are available on the front of the Micrologic X control unit.

  1. The PreWarn/Warn LED is a bicolor LED with two functions:

    1. PreWarn/Warn LED changes to orange when I > 0.9 Ir

    2. Warn LED changes to red when I > 1.05 Ir

  2. The Ir LED is dedicated to long time overload protection, it changes to red when the protection trips.

  3. The Isd/Ii LED is dedicated to short-time and instantaneous short-circuit protection. It changes to red with a short-time or instantaneous overcurrent event.

  4. The Ig/IΔn LED is dedicated to ground-fault protection. It changes to red when that protection trips.

  5. The Op. LED is dedicated to the optional protections and changes to red when any of the optional protections trip.

The fault indication LEDs remains ON four hours after trip if not reset by the test/reset pushbutton. After four hours without reset it is possible to reactivate the trip indication LEDs by pushing the test/reset pushbutton. Under normal operating conditions, the battery supplying the LEDs has a service life of approximately 10 years.

The battery charge is continuously monitored.

Trip History

Trip history is captured and stored in the control unit, and can be retrieved and evaluated using Ecoreach™ software and the MTZ app.

Each trip inside the trip history (except the last one) includes:

  • Type of protection that caused the trip: long-time (overload), short-time (short-circuit), instantaneous (short-circuit), ground fault.

  • Date and time of the fault.

The last 50 trip histories can also be retrieved by means of a PC running Ecoreach software.

In addition, Micrologic X control unit also logs:

  • Last electrical values measured before the fault (voltages, currents, frequency, current and voltage unbalance levels),

  • Tripping current during the fault just before the Masterpact MTZ circuit breaker trip (phase, neutral and ground currents).

  • Protection settings.

The last trip may be retrieved through the NFC powerless wireless communication while the circuit breaker is open and the Micrologic X control unit is not energized.

Protection Settings and Checking

The protection settings can be set by means of the embedded display, a smartphone via Bluetooth technology, or with Ecoreach software running on a PC.

Ecoreach software allows:

  • Setting and checking the protections.

  • Downloading current settings and uploading new settings.

  • Checking the circuit breaker operation.

  • Retrieving and displaying information processed by the Micrologic X control unit:

    • Measurements,

    • Alarms,

    • Warnings,

    • Diagnostics.

  • Generating and storing reports.

Setting Change Traceability

Setting changes are recorded in the protection history, including:

  • Date and the time of the last setting change.

  • Previous settings and new settings.

The NFC wireless connection allows access to the active trip settings while the circuit breakers is Open and the Micrologic control unit is not energized.

Setting Change Locking

The general configuration menu of the Micrologic X control unit’s embedded display allows:

  • Enabling or disabling the protection setting change from the embedded display.

  • Enabling or disabling the protection setting change from external access:

    • Smartphone via Bluetooth technology,

    • PC running Ecoreach software,

    • Ethernet and Modbus SL (RTU) communication.

Zone-Selective Interlocking (ZSI)

ZSI is a system designed to reduce the stress on electrical distribution equipment during short-circuit or ground-fault conditions. It uses previously-coordinated protection to reduce the fault tripping time while maintaining selectivity. Each version of the Micrologic X control unit includes the ZSI function. The ZSI function is associated with short-time short-circuit protection and ground-fault protection.

The control unit detecting a fault sends a signal upstream and checks for a signal arriving from downstream. If there is a signal from downstream, the circuit breaker remains closed for the full duration of its tripping delay. If there is no signal from downstream, the circuit breaker opens immediately, regardless of the tripping-delay setting.

Zone selective interlocking can be implemented between all types of Masterpact MTZ circuit breakers.

When ZSI connects Masterpact MTZ circuit breakers with circuit breakers other than Masterpact MTZ, it may be necessary to use a ZSI Interface Module.

Fault 1

Only circuit breaker A detects the fault. Because it receives no signal from downstream, it trips with no intentional delay, regardless of its tripping delay set to 0.3.

Fault 2

Circuit breakers A and B detect the fault. Circuit breaker A receives a restraint signal from B and remains closed for the full duration of its tripping delay set to 0.3. Circuit breaker B does not receive a signal from downstream and opens immediately, in spite of its tripping delay set to 0.2.

Limits to Device Interconnection:

  • A maximum of 15 upstreams devices may be connected to the ZSI input (Z1-Z2).

  • A maximum of 15 downstream devices may be connected to the ZSI input (Z3-Z4). If additional units are needed, a ZSI Interface Module is required.

ZSI Interface Module (ANSI 78)

The ZSI Interface Module in a ZSI system with Masterpact MTZ circuit breakers equipped with Micrologic X control units:

  • Boosts the voltage level of the restraint signal.

  • Converts the restraint signal to be compatible with other types of Schneider Electric™ circuit breakers (Masterpact NT/NW) and Square D™ circuit breakers.

  • Provides double insulation to meet requirements of IEC standards when upstream and downstream are different generations of devices (Masterpact MTZ, Masterpact NT/NW).

Within a ZSI system, the voltage level of the restraint signal must be maintained at a certain level in order to activate the time delay of electronic trip devices.

If the restraint signal is too weak to activate the time delay feature, all devices that sense the fault will trip with no intentional delay.

The voltage level of the restraint signal can be ineffective due to:

  • Restraint wire length exceeding 300 m (984 ft.).

    If restraint wire length exceeds 300 m (984 ft.), the voltage drop along the control wire will weaken the restraint signal until it can no longer activate the time delay on the upstream device. If wire length exceeds 300 m (984 ft.), a ZSI module must be placed in the circuit to boost the voltage level of the restraint signal.

  • One device sending a restraint signal to many devices.

    In addition, if the number of upstream circuit breakers exceeds 15, then a ZSI module is required.

  • Varying signal levels from different electronic trip systems.

For further details on allowable ZSI combinations, please refer to the ZSI interface module installation bulletin NHA12883.


  • Maximum rated operational voltage (V): 690 Vac, 50/60 Hz.

  • Power supply: 24 Vdc +25/-20% , 6 mA.

  • Maximum operating temperature surrounding the module when installed inside electrical equipment: -35°C to 75°C (-31°F to 167°F).

  • Standards compliance: IEC 60950-1, CISPR 22, CISPR 24, UL 489, UL 489SE.

  • CE marked according to LVD (Low Voltage Directive 2014/35/EU) EN 60950-1 and EMC directive (2014/30/EU) EN55022, EN55024

Connection & Installation

  • Terminal strips, jumpers and 35 mm DIN mounting rail (IEC/EN 60715).

  • Twisted wire with a braided shield, 300 Vac, 2.5–0.4 mm2 (22 AWG).

Instantaneous Override Protection and Close and Latch Ratings

The instantaneous override and close and latch are fixed trip settings to protect the circuit breaker when there is a high fault condition. These settings are typically higher than the standard instantaneous setting and function without regard to any other protection settings.

Instantaneous override is a fixed trip setting to open the circuit breaker, under 25 ms, in the event of fault which exceeds the instantaneous override trip value.

The close and latch rating is a fixed trip setting set lower than instantaneous override, to protect the circuit breaker in the event of closing the circuit breaker on an existing fault condition. After 20 ms the circuit breakers reverts to the "instantaneous override" setting.

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