Abstract: A power switching apparatus comprising a current transformer with coupled primary and secondary windings, the primary windings being adapted for series connection between alternate current power source and load, the primary windings comprising first and second sub-primary windings of different number of turns of windings and respectively of a larger and a smaller core diameter, a current conduction path being provided from intermediate the first and the second sub-primary windings to the power switching means so that upon detection of a current exceeding the current rating of the second sub-primary windings, current will be caused to flow from alternate current power source to load via a current loop comprising the power switching means and the first sub-primary windings only.