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4.3 Requirements of the mid-voltage power transformer connected to the
(double) central inverters
The transformer in the figure allows only a double stack (four-winding) transformer and a three-winding
transformer with LHL winding. In such MV transformer, a high-voltage winding is placed between two
low-voltage windings.
This transformer shall comply with the following technical specifications.
Equivalent series impedance between low-voltage and high-voltage windings:
The equivalent series impedance Z(%) of the transformer shall be 6% in every instance for each inverter.
The impedance voltage allowable criteria of 5.4% to 6.6% shall be maintained. This value can be
determined when the voltage in other low-voltage winding increases until the high-voltage winding is
short-circuited and a nominal current flows. Simultaneously, other low-voltage winding is in the idle
state.
