Parameters Affecting the Performance of Transformers Under Short Circuit - A CPRI Experience

Transformers are basic electrical machines and they form a very vital link in any electrical power transmission networks. During its service life, a transformer may experience number of short circuits in the system in addition to the abnormal overloading and switching impulses. Such abnormal conditions can cause the movement of the windings and failure of the supporting structures due to electro – mechanical forces and may result in total failure due to inadequacy in design and defective manufacturing process. Further, the rapid growth of fault level in the system network is major a concern for short circuit withstand capability of a transformer in service for a long period of time. With advanced modern technology and available short circuit test facilities, transformer manufacturing industry is now enabling to produce the reliable and safe transformers. Performance evaluation during ability to withstand short circuit test in a fully equipped testing laboratory is still final measure of checking the overall quality of the transformer from the point of design, material used, production process and quality control. Central Power Research Institute (CPRI), is having an experience of more than fifty years in the fi eld of short-circuit testing. The roles of various factors which affect the performance of transformers under short-circuit conditions are discussed along with the analysis of the failure cases during the short circuit testing.