Evolution of Long Duration Current Impulse Withstand Test on Surge Arresters for H.V.A.C. Systems

The paper enlightens the parallel development of the characteristic of the arresters and of the procedure to test their capability to discharge the energy during operation consequent to switching overvoltages, test called "long duration current impulse withstand (LDCIW) test". It is shown that the procedure for the LDCIW test prescribed in the current edition of IEC Publication 99-1 (1970) is strictly related to the peculiar features of active-gap arresters, and that is not necessary to adopt it also in the Draft of Standards for metal-oxide arresters (MOA) under preparation by IEC TC 37 "Surge Arresters". The main drawback of this procedure is that it requires a large number of different test circuits if a laboratory intends to be equipped for testing arrester sections of all classes and all rated voltages. An alternative test procedure for LDCIW tests on MOAs is described and analyzed, which is equivalent to that proposed in the mentioned Draft. It practically requires only one test circuit, and implies smaller tolerances on the energy stress on the arrester, so making the test more reproducible. It is finally shown that the alternative test procedure can be improved to test arresters against any kind of switching overvoltages, and not only to line discharge, as the current procedure.