Air-core reactors are a wound inductance utilising one or more windings in parallel. Insulated aluminium stranded cables are wound on a mandrel, with the final coil being impregnated with epoxy resin and painted to provide the finished reactor. The finished coils are mounted on station post insulators and (where necessary) galvanised steel structures.
Air-core reactors can be supplied in stacked, side-by-side or triangular configuration depending upon physical and site constraints.
Air-core dry type reactors do not utilise an oil insulation system or an iron core. They are environmentally friendly and do not provide any fire hazard.
Air-core reactors have a number of key applications in transmission and distribution networks:
- Fault current limiting reactors
- Load flow control / line balancing reactors
- Inrush current limiting and de-tuning reactors for capacitor banks
- Harmonic filters reactors
- Shunt reactors
- Neutral earthing reactors
- TCR, SCR & filter reactors for Static VAR compensation systems
- DC smoothing and filter reactors for HVDC systems
- Electric arc furnaces reactors
- Line traps utilized for PLC protection
Air-core reactor windings are manufactured either with one single layer or several layers in parallel. Stranded cables are used; they are insulated with high performance film insulation and woven tape. The windings are arranged radially with fibreglass spacers that provide vertical ducts for convection cooling of the windings.
The windings are completed by impregnation with epoxy resin to provide superior electrical properties and high resistance to weathering. All surfaces are finished with UV resistant paint. In areas of heavy pollution, an additional silicone coating can be applied to eliminate the risk of surface tracking.