Graph-Analytical Method of Determining Impedance in Electrical Transformers

Abstract EN

This paper presents a graph-analytical method for determining the electrical impedance of alternate energy sources, especially small power transformers and current transformers in electric networks.

Unlike conventional short-circuit and idle tests, according to proposed method, in this paper, transformer parameters are determined in a new way, which is based on measurement of voltages and currents on the active and reactive load (inductive or capacitive).

The effectiveness of the proposed model was verified using an adapted simulation in the software package MATLAB Simulink.

The simulation was performed for three types of ABB transformers with a 100% load.

Simulation results were obtained for power transformers: Sn1=1 [MVA], Sn2=2 [MVA], Sn3=3.15 [MVA].

If we compare measurement result values of RT, XT, which are contained in a brochure for ABB transformers and those obtained through simulation, different tolerances are obtained.

For reactance results, deviations are up to 20% for all three tested transformers.

For results of active resistance tolerances are up to 5% for all three tested transformers.

This method can be used not only to determine the active and inductive AC power source parameters but also to determine and analyze the impendence of electrical sources with high frequencies.