## Answers

Jul 03, 2015 - 12:26 AM

Hi,

in order to model any transformer using 3 phase 2 winding transformer model, you normally need the parameters given in the transformer nameplate (with some modifications).

As for the parameters you ask about, positive sequence leakage reactance is the per unit value of short circuit test voltage (sometimes named as Uk), in your case 5/100 = 0.05.

No load losses and magnetizing current are determined during open circuit test and correspond to the parallel branch in the transformer model, but I guess you don't have the relevant data. As base apparent power PSCAD uses the transformer apparent power.

The same applies to copper losses, but you don't have copper losses, only R/X ratio, so if you need to include R in your model, you need to calculate the losses using the formula R=(Pk/Sn)*(U^2/Sn), where Pk - losses in physical units, Sn - transformer rating, U - voltage.

UMEC transformers are explained in PSCAD help, you can use them for example for modelling 3-limb three-phase transformers (3 phase 2 winding transformer model is basically based on 3 single phase units).

Cheers,

Marcin

in order to model any transformer using 3 phase 2 winding transformer model, you normally need the parameters given in the transformer nameplate (with some modifications).

As for the parameters you ask about, positive sequence leakage reactance is the per unit value of short circuit test voltage (sometimes named as Uk), in your case 5/100 = 0.05.

No load losses and magnetizing current are determined during open circuit test and correspond to the parallel branch in the transformer model, but I guess you don't have the relevant data. As base apparent power PSCAD uses the transformer apparent power.

The same applies to copper losses, but you don't have copper losses, only R/X ratio, so if you need to include R in your model, you need to calculate the losses using the formula R=(Pk/Sn)*(U^2/Sn), where Pk - losses in physical units, Sn - transformer rating, U - voltage.

UMEC transformers are explained in PSCAD help, you can use them for example for modelling 3-limb three-phase transformers (3 phase 2 winding transformer model is basically based on 3 single phase units).

Cheers,

Marcin

Jul 03, 2015 - 10:52 AM

Thank you Marcin. It does not seem practical that we do the open circuit and short circuit testing for each transformer in the system to model it correctly. How much do you lose if copper losses and magnetic losses are not incorporated in the transformer model? i.e. only modeling the leakage impedance and assume 0.2% magnetic losses and 0.5% load losses.

Also, Do you have a reference for average magnetic and copper losses in transformers that can help?

Also, Do you have a reference for average magnetic and copper losses in transformers that can help?

Add New Comment