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GENERAL
10
NC020 - Manual - 05 - 2022
2 G E N E R A L
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Preface
In recent years the harmonic producing part of total load has increased continuously because of the
massive usage of power electronic in all the voltage levels. Thyristor convertors, Frequency con-
vertors, thyristor switches and static var compensator, such as thyristor controlled reactors (TCR)
and thyristor switched capacitors (TSC), are commonly adopted in industrial applications and power
utilities.
Filter capacitor banks consist of capacitor bank and series connected air core. Their task is to ab-
sorb the harmonic currents generated by loads and all above mentioned power electronic devices.
The aim of NC020 is to provide a reliable and cost effective solution for such an application granting
capacitor bank safe operations.
The capacitor banks may have the following configurations:
• Single Wye grounded.
• Single Wye ungrounded (with a resistor on the output of the neutral unbalance voltage transformer
in order to develop the appropriate input current for the unbalance protection).
• Double Wye ungrounded.
A suitable compensation method is provided to compensate the inherent unbalance neutral cur-
rent.
Protection 50/51 RMS is based on RMS value measurement of the three phase currents (fundamental
and harmonics up to the 23th).
The peak capacitor voltage is calculated (fundamental frequency and harmonics up to twenty-third
order) for any phase by means of integration of measured line currents without requiring the instal-
lation of VTs for the direct measurement of the capacitor voltages.
Following input circuits are available:
• Three phase current and one neutral current inputs with rated currents independently selectable
at 1 A or 5 A using DIP-switch (CT inputs).
• Three binary inputs.
Setting, programming and reading operations must be effected by means of Personal Computer with
ThyVisor software or by means of remote communication interface (RS485 bus); all operations must
be performed through MMI.
The NC020 hardware case is suitable for flash and rack mounting
Other options are:
• Auxiliary power supply operating range.
• Communication protocols (Modbus RTU).