How do you model the frequency dependent resistance of transformers for harmonics studies?
The transformer impedance is mainly influenced by the series leakage inductance and copper losses for harmonic studies based on Harmonic Load Flow Calculation and Network Impedance Frequency Sweep Calculations.
The series leakage inductance corresponds to the fundamental frequency inductance over the relevant frequency range for most cases.
The copper resistance on the other hand are highly frequency dependent. The frequency dependency is modeled based on characteristics as follows:
- Create a Frequency Scale (TriFreq) e.g. from 1 Hz to 2.5 kHz
- Create a Parameter Characteristic - Vector (ChaVec)
- Select the TriFreq
- Assign the characteristic e.g. from the attached Excel sheet as relative p.u. values
- Assign the ChaVec on the Harmonics page of TypTr
The frequency characteristic is either provided from the manufacturer or based on typical values in the literature.