WTG fault contribution calculations

[vc12345]

Hi,

Please would anyone be so kind to provide some help on the following.

I have a wind turbine generator connected in series with a wind turbine transformer.

I want to calculate the fault contribution in MVA at 33kV terminals of the 33/0.66kV transformer.

I have a WT generator with fault contribution of 9.55kA at 660V. Its a 2.5MW generator. Rated at 2.525MVA.

The generator transformer is 33/0.66kV, rated at 3.15MVA. R = 0.3175 pu on 100MVA base, X is 2.539 pu on 100MVA base.

Thanks

 

[cuky2000]

The SC contribution of the wind turbine generator (WTG) even if connected in series with a transformer will depend on the
following factors:

a) Equipment Characteristics, configuration and number of WTG and transformers interconnected
b) type of the installed WTGs:
b.1) [u]Type 1 & 2 WTGs[/u]: SC current will be determined by the physical characteristics of the induction generator impedances.
b.2) The WTG Type 3 & 4 SC will be mostly characterized by the power AC/DC/AC BTB power converter’s.

See the enclose article for additional details in this subject.

http://www.nrel.gov/docs/fy10osti/47193.pdf

 

[krisys]

cuky2000,
The article is informative. The current IEC-60909 standards are not giving any special treatment to the WTG short circuit current contribution. I feel, the field of Wind Turbine Generation (WTG) is still emerging, you should consider the worst case of short circuit contribution scenario (i.e.; based on WTG Type-1) for the equipment design.

 

[m3ntosan]

Based on the size and the current contribution,I'll take it this is a type 3 DFIG and the 9.5kA would be the initial symmetrical short circuit current for a fault applied on the HV side of the transformer. The DFIG behaviour depends very much on the converter, the control system will react differently depending on the retained voltage and if it's trying to do fault ride through or not. Is generally acceptable to consider induction machine behaviour for the first 50ms and assume after that the current contribution is controlled by the converter to a value of 1.5 - 1 time the rating of the turbine.

Since it's a bit of a finger in the air,for the HV side of the transformer I would assume 6x for peak and between 3-4x for the initial symmetrical short circuit current and down to 1.5-1x for RMS break at 90-100ms. This could be a conservative approach if you use the fault current contribution for switchgear assessment, but if you want worst case for protection calculation for fault further in the network I would consider the retained voltage would be reasonable and the converter controls the fault contribution to 1.5x to protect its electronics.





May you grow up to be righteous, may you grow up to be true...