Protective Devices; Capacitor Fuses; Inrush-Limiting Reactors; Cooling Of Scr/Diode Valves - S&C PureWave AVC Instructions For Installation And Operation Manual

Adaptive var compensator

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Table of Contents

Capacitor Fuses

Inrush-Limiting Reactors

Cooling of SCR/Diode Valves

Heat-Sink Temperature Sensor

Surge Arresters

Frequency Scan

Each capacitor stage consists of groups of capacitor cells mounted on

modular trays. Each capacitor stage is protected by a semiconductor-

grade fuse.

Some PureWave AVCs are ﬁtted with detuning reactors. These reactors

prevent resonance-related problems and limit the rate of rise of SCR

current to limits speciﬁed by the SCR supplier.

Each SCR/diode heat sink includes a thermostatically controlled cool-

ing fan. The cooling fan is turned on when the temperature at the sur-

face of the heat sink exceeds 60° C. The fan turns off when the heat

sink temperature cools to 45° C.

A temperature transducer, mounted on each SCR/diode heat sink, dis-

ables the triggering signal for that capacitor stage if the temperature

reading on the surface of the heat sink exceeds 85° C, which is indica-

tive of fan misoperation. Normal operation will resume when the heat

sink temperature cools.

The PureWave AVC is provided with high-energy MOV surge arresters

that offer protection against transient overvoltages in the power sys-

tem. The arresters are placed at the cable entrance.

Synchronization of the SCR triggering times, set by the control pro-

gram, is based on the zero crossing of the phase-to-neutral voltages. To

avoid SCR misﬁres due to voltage waveform distortion, the micropro-

cessor timing block calculates the time between two consecutive zero

crossings. If the duration does not correspond to the 60-Hz power fre-

quency, SCR ﬁring signals are disabled for one cycle, or until the volt-

age waveform returns to normal.