Real-Time Measurements

Presentation

MicroLogic X control units perform the following real-time tasks:

• Measure the following currents in real time and as an RMS value:

  • Current for each phase and the neutral (if present)

  • Ground-fault current

  • Earth-leakage current (MicroLogic 7.0 X)

• Calculate the average current in real time

• Determine the maximum and minimum values for these electrical quantities

• Measure the phase-to-phase and phase-to-neutral voltage (if present), in real time and as an RMS value

• Calculate the associated electrical quantities from the RMS values of the currents and voltages:

  • Average phase-to-phase voltage and phase-to-neutral voltage (if present)

  • Current unbalances

  • Phase-to-phase voltage unbalances and phase-to-neutral voltage unbalances (if present)

• Calculate the associated electrical quantities from the current and voltage samples:

  • Powers

  • Quality indicators: frequency, THD(I), THD(V), THD-R(I), and THD-R(V), and power factor PF and cos φ measurement

• Display operating indicators: quadrants, and type of load

• Determine the maximum and minimum values for these electrical quantities

• Increment in real time three energy meters (active, reactive, apparent) using the total power real-time values

The sampling method uses the values of the harmonic currents and voltages up to the fifteenth order. The sampling process tracks the fundamental frequency and provides 40 samples per fundamental cycle.

The values of the electrical quantities, whether measured or calculated in real time, update once a second at rated frequency.

System Type Setting

On 3-pole circuit breakers, the system type setting allows the activation of:

• The ENCT (external neutral current transformer)

• The ENVT (external neutral voltage tap)

The system type can be set as follows:

• On the MicroLogic X display screen, at Home > Configuration > Measures > System Type.

• With EcoStruxure Power Commission software (password-protected)

• By sending a setting command using the communication network (password-protected)

Measuring the Neutral Current

Measuring the Ground-Fault Current

The ground-fault current is calculated or measured in the same way as the phase currents, according to the circuit breaker configuration, as shown in the following table.

Measuring the Earth-Leakage Current (MicroLogic 7.0 X)

The earth-leakage current is measured by a rectangular sensor encompassing the three phases or the three phases and neutral.

Measuring the Phase-to-Neutral Voltages

4-pole circuit breakers, or 3-pole circuit breakers with the ENVT wired and configured, measure the phase-to-neutral (or line-to-neutral) voltages V1N, V2N, and V3N:

• For a 3-pole circuit breaker, it is necessary to:

  • Connect the wire from the ENVT to the neutral conductor

  • Declare the ENVT in the system type setting

• For 4-pole circuit breakers, the phase-to-neutral voltages are measured systematically.

The phase-to-neutral voltages are measured in the same way as the phase-to-phase voltages.

Calculating the Average Current and Average Voltage

MicroLogic X control units calculate the:

• Average current Iavg, the arithmetic mean of the 3 phase currents:

  

• Average voltages:

  • Phase-to-phase Vavg, the arithmetic mean of the 3 phase-to-phase voltages:

    

  • Phase-to-neutral Vavg, the arithmetic mean of the 3 phase-to-neutral voltages (4-pole circuit breakers or 3-pole circuit breakers wired and configured with the ENVT):

    

Measuring the Current and Voltage Phase Unbalances

Maximum/Minimum Values

The MicroLogic X control unit determines the maximum (MAX) and minimum (MIN) value reached by the following electrical quantities for the period from the last reset to the present time:

• Current: phase and neutral currents, average currents, and current unbalances

• Voltage: phase-to-phase and phase-to-neutral voltages, average voltages, and voltage unbalances

• Power: total power and phase power (active, reactive, and apparent)

• Total harmonic distortion: the total harmonic distortion THD and THD-R for both current and voltage

• Frequency

• The maximum of the maximum value of all phase currents

• The minimum of the minimum value of all phase currents

• The maximum of the maximum value of 3 phase current unbalances

• Maximum of maximum of 3 phase-to-phase voltage unbalances

• Maximum of maximum of 3 phase-to-neutral voltage unbalances

Resetting Maximum/Minimum Values

The maximum and minimum values can be reset as follows:

• On the MicroLogic X display screen, at:

  • Home > Measures > Current

  • Home > Measures > Voltage

  • Home > Measures > Power

  • Home > Measures > Frequency

  • Home > Measures > I Harmonics

  • Home > Measures > V Harmonics

• With EcoStruxure Power Commission software

• With the EcoStruxure Power Device app

• By sending a command using the communication network (password-protected).

• On the IFE/EIFE webpages

All maximum and minimum values for the group of electrical quantity selected are reset.

Resetting maximum and minimum values generates the following events: