APFC Relay

The Novar 1106, 1114 reactive power controller is a fully automatic instrument that allows optimum control of reactive power compensation.
It contains precise voltage and current measurement circuits, and high precision evaluation of both root–mean–square (RMS) current and the power factor is achieved through digital processing of the values measured.
The 230 V AC supply terminals also work as the measurement voltage input. The current measurement input is a general–purpose one for the nominal secondary winding current value of a current measuring transformer (CMT) 1A or 5A. Current of any of the phases can be measured.
The instrument calculates the fundamental harmonic component of the active and reactive currents using the FFT algorithm. Thus precise measurement and control are provided even if the current waveform is distorted by higher harmonic components.
Controlling takes place in all four quadrants and its speed depends on both control deviation value and its polarization (overcompensation undercompensation). Connecting and disconnecting power factor capacitors is carried out to achieve the optimum compensation condition with a single control step and minimum number of switching on or off the sections. At the same time, the instrument chooses the sections with regard to their even load and preferably connects those that have been disconnected for the longest time and the remanent charge of which is thus minimum.
While controlling, the instrument continually checks the compensation sections. If a section’s drop–out or value alteration is detected, the section is temporarily disabled at relevant setting. The section temporarily disabled is periodically tested, while control is in progress, and possibly enabled again.
In measurement of current, harmonic component levels are evaluated of up to the nineteenth order. The total harmonic distortion, THD, which can be viewed on a display, is calculated from these measurements’ results.