Air-cored shunt reactors

The Air-cored Shunt Reactors manufactured by Smit Transformatoren are used in a variety of circumstances. They consist of a single coil (essentially an air-cored inductance) for each phase located within a magnetic shield. The magnetic shield provides a low loss path for the magnetic flux produced by the windings. If this magnetic shield was not provided, the magnetic flux could cause unwanted heating of any mild steel parts in the vicinity of the windings.

A typical application of Shunt reactors is power factor compensation of a circuit, for example to compensate for the capacitance of long overhead transmission line or for much shorter lengths of HV cable. At low loads, the remote end of these lines may rise in voltage (the so called “Ferranti Effect”). This is especially prevalent in developing countries where the system may be only lightly loaded in the early years following installation. The large coils of the shunt reactor provide inductive compensation to guard against this effect. Other advantages of shunt reactors include the prevention of generator self-excitation on leading power factor loads and the reduction of over-voltages on sound phases following a single line-to-ground fault.