Rated power of earthing transformer

[lz5pl]

In our current project we have 33 kV grid of wind farm with 33 kV earthed via earthing transformer and neutral earthing resistor in step-up (33/110 kV) substation. I am working now on the model of the grid for short circuit currents calcualtion and relay protection coordination.
In the software I have to input some transformer data, as rated zero sequence active and reactive power, rated zero sequence short circuit voltage (%). Can somebody help me with any typical data for similar transformer? Grid voltage is 33 kV, earth fault current have to be limited to 300 A/10s, neutral earthing resistor is 63 Ohm.

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[waross]

Calculate the zero sequence values based on the current through the earthing resistor. The impedance of the earthing resistor will predominate. Ignoring the transformer impedance will introduce a slight error but only a few percentage, and the actual current will be slightly lower than the calculated current.
If you want a more precise answer and an answer for the reactive power you will have to tell us the PU impedance of the transformer and the X:R ratio.
For short circuit voltage you may use 3^2 (1.73) of the line to line voltage.
I suggest doing the calculations, based on just the value of the earthing resistor as a reality check. When you calculate the values with the transformer impedance included, you should be within a few percent. Any more and you should recheck your method.
Exception; The short circuit reactive current will be much reduced by the introduction of the earthing resistor so the reactive power (I^2.R) will be much much reduced compared to a calculation based on the value of the earthing resistor alone.

Bill
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"Why not the best?"
Jimmy Carter