Standards Development

Scope

This part of IEC 60076 establishes the requirements for power transformers to sustain without damage the effects of short-circuit currents resulting from external short-circuits. It describes the calculation procedures used to demonstrate the thermal ability of a power transformer to withstand such short-circuit currents and both the special test and the theoretical evaluation method used to demonstrate the ability to withstand the relevant dynamic effects. The requirements apply to transformers as defined in the scope of IEC 60076-1.

Note 1: The calculation and tests assumes that the transformer will be already energized at the time of short-circuit. The design calculation usually considers that there is a perfect balance of ampere-turns between the two windings. This may not be always the case during tests and under short-circuit conditions in the network. For particular designs of transformers energized from an inner winding or with axially split windings this may be significant and needs to be considered because the transformer may not be strong enough to survive a pre-applied fault.

Note 2: The currents resulting from out-of-phase synchronization are not considered.