Energizing the different elements of the electrical power system, like transformers, capacitor banks or reactors, goes always together with the risk of transient overvoltages and overcurrents. De-energizing these elements can result also in overvoltages and restriking. For instance, Energizing an unloaded transformer often causes inrush currents of extreme high magnitudes. This is harmful to the mechanical structure and insulation of the windings, and shortens the lifespan of the transformer.
The most efficient handling of these problems is the elimination of the root cause: finding an optimal moment for the energizing and the de-energizing. The aim of the controlled switching is to find this moment (point-on-wave) and to delay the close and the open command to the circuit breaker accordingly. The different electrical equipment needs naturally different energizing strategy because of their different physical characteristics. The Point-on-Wave switching (PoW) functionality is applicable for controlled energizing and de-energizing of reactors, capacitors and power transformers (as TRIM function).
