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.
