Design margin for short circuit withstand capability in large power transformers

The short circuit test in a power transformer is a special test that establishes confidence in the designer and user in the integrity of the winding. Conventional tests rely on the measurement of reactance before and after the test in order to assess failure. We propose alternative method on a cycle to cycle basis based on continuous evaluation of certain phasors as well as real and reactive power measurement. Further we propose model tests based on FEM analysis of windings in conjunction with video recordings. The objective is to establish a design margin for the withstand capability at the laboratory stage which will be more instructive than mere Go/No-Go tests. The method will also directly useful in situations where a complete transformer cannot be tested due test facility limitations. All the proposed methods are demonstrated through tests on windings. © 2007 RPS.