Transferences, surge arresters

Surge protection on HV side is adequate to absorb direct surges. The transferred surges from HV side to the LT side are too feeble to cause any harm. In case of static switchings, on LT side, however, spike arrester will be essential. Section 6.14.1. 

The BIL of the interconnecting cables and the terminal equipment on the secondary must be at least equal to the capacitive and Inductive transferences of the primary surges as determined above. If it is not so, the of the primary arrester must be re-chosen or an arrester also provided on the secondary side. 

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