While all individual components of a substation are tested in factory, it is equally necessary to check if their transportation and interconnection has compromised any of its performance ratings. Testing at site is an integral part of the commissioning of any HV/EHV equipment. Site testing has more primacy in most parts of the world. In fact even large Transformers, CTs, PTs, Bushings, Cables are tested for HV, Loss & Impulse at site. Apart from testing during fresh commissioning, it is most essential to do these tests specially when an EHV equipment is repaired at site. These site testing requirements are now also being widely demanded by end-customers in developing countries like India.