Group 1 and group 2 have to be homogeneous, which means they can measure 3
currents or 3 voltages. For example, measurement of 1 current and 2 voltages is not
allowed. Group 3 can get any type of signals, for example, 2 currents, 2 voltages, or
1 current and 1 voltage. REF 542plus analog input is designed to be very flexible in
order to support all the protection functions of the unit itself.
Group 1 and group 2 can be used for homogeneous current or voltage measurements
both from instrument transformers and non-conventional sensors. Group 3 can be
used in a heterogeneous way, but in most cases with instrument transformers only.
For example channel 7 in group 3 can be used for earth-fault current with current
transformer type input, or for the synchro-check function with voltage transformer
type input.
The most common configuration uses three current and three voltage inputs and one
earth fault current input. All values are shown on the display as primary values. The
values registered over an extended time period, for example, energy, number of CB
operations, and maximum and measurement values are permanently saved. Even
after power interruptions this data is still available. Using this common
configuration, the following measured values are displayed:
4.2.1.
Directly measured values
*
Phase currents, three phases
*
Phase line voltages, three phases
*
Residual current (it can be calculated)
*
Residual voltage (it can be calculated)
*
Frequency
4.2.2.
Calculated values
The following values can be calculated from the measured quantities listed above:
*
Phase or Line voltages, three phases
*
Average value/maximum value current, three-phase (determined over several
minutes)
*
Apparent, active and reactive power
*
Power factor
*
Active and reactive energy
*
THD (total harmonic distortion)
4.2.3.
Other values
Moreover, the following quantities can be provided for monitoring purposes:
*
Operating hours
*
Switching cycles
*
Total switched currents
*
Metering pulses from an external metering device (up to 10)
20
REF 542plus
REF 542plus
Multifunction Protection and Switchbay Control
Unit
Technical Reference Manual
1MRS755859
