The ability to withstand the dynamic effects of short-circuit shall be demonstrated by testing or by calculations as per IEC60076-5 and IS 2026-5. Thermal ability to withstand short-circuit is always demonstrated by calculations. No testing is required to demonstrate the thermal ability to withstand short-circuit for the transformers as per IEC60076-5 and IS 2026-5. Occasionally, thermal ability of transformers has been tested as additional requirement by the manufacturer, after the dynamic short-circuit test. There are instances where the transformers failed in thermal short-circuit test, even after successful completion of dynamic short-circuit test. They have successfully demonstrated thermal ability to withstand short-circuit by calculations. This paper discusses the significance of long duration short-circuit test in the light of IEEE std C57.12.90.
Short-circuit currents, Temperature, Thermal stresses
