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Two-winding Transformer Phase Shift in IEC Short Circuit

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For two winding transformers, EasyPower supports phase shifts of 30, 90, 150, 210, 270, and 330 degrees [as per IEC 60076-1 p. 35-37]. IEC uses a “clock number notation” system. In that system, 1,3,5,7,9 and 11 correspond to 30, 90, 150, 210, 270 and 330 degrees anticlockwise.

The database report and one-line display use capital letters to denote the HV side. The LV side is denoted by lower case letters.

EasyPower compares the “From” and “To” sides to specify which side is the reference (with the “HV” side being the reference). In cases where both sides have equal voltage, EasyPower assumes the “From” side to be the reference.

This is applicable only to D-Y (or Y-D) transformers.

For a 30-degree phase shift, the positive sequence is rotated +30 and the negative sequence is rotated -30 degrees.

Zero sequence current won’t flow through a DY transformer.

Transformer phase shift selection

One-line diagram

When BUS-1 is faulted, the results for positive sequence is shown with different phase shifts for each transformer.

One-line diagram illustrating effects of phase shift on short circuit results

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