Short Circuit Requirements 

PSTs shall comply with the short circuit requirements of IEEE Std C57.12.00-2000, unless otherwise agreed upon by the purchaser and manufacturer.

Transformer categories
The kVA rating to be considered for determining the category should be the equivalent to the rating according to IEEE Std C57.12.00-2000.

Short-circuit current magnitude
The manufacturer shall determine the most onerous conditions for short circuit on every winding or active part in accordance with IEEE Std C57.12.00-2000.

These conditions should take into account the large impedance swings that can occur as the tap position is changed from the extreme positions to the mid position.

Since the system short-circuit levels are critical to the design of PSTs, the user shall specify the maximum system short-circuit fault levels expected throughout the life of the unit.

If a short-circuit test is performed, it shall be done in accordance with IEEE Std C57.12.90-1993.

The test shall be carried out on the tap position that produces the most severe stresses in each winding. This may require more than a single test depending on the type of construction.

For two-core PSTs this usually requires a test on the zero phase-shift position, as this position involves only the series transformer, and a second test on a position to be agreed upon between customer and manufacturer.

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