SFRA Capability for detection of deformation in transformer windings: a field experience of 400kV 167MVA single phase ICT [articol]

Abstract

Sweep Frequency Response Analysis has become very popular now – a - days due to its ability to provide comprehensive information regarding mechanical as well as electrical condition of power transformers. The SFRA is a signature test and provides better information when evaluation of Transformer condition is done by comparing actual set of SFRA results with reference results. This field experience refers to 400/220/33KV ICT bank, formed with three single phase units – each with capacity of 167MVA. Heavy fault current was fed through ICT due to failure of LA provided on external delta formation of Tertiary winding. Mechanical defects / deformation occur ostensibly due to short circuit current flowing through transformer winding in case of terminal faults i.e. fault adjacent to / on the power transformer. To ascertain mechanical integrity of power transformer, SFRA test is carried out and is supported by other tests i.e. capacitance and tan delta measurement etc. The test results reveal that SFRA is capable of providing more information about mechanical deformation of active parts of power transformers - compared to other tests.