Online detection method of distribution transformer loss under harmonic disturbance

To study the online calculation method of harmonic no-load loss and harmonic load loss by using the voltage and current data of the high and low sides of the distribution transformer. Firstly, the calculation method of harmonic loss is deduced by analyzing the variation of no-load loss with frequency and flux density. Then, the least square method is used to identify the fundamental wave resistance of the winding, and the winding resistance loss model under harmonic conditions was established according to the Γ-type equivalent circuit and superposition principle of the transformer. Subsequently, based on the proportional relationship between the load losses in the improved IEEE method, the online acquisition method of harmonic load loss with Dyn11 and Yyn0 connection modes is obtained. The influence of harmonic and load variation on harmonic loss is analyzed. The computation and testing outcomes demonstrate that the proposed approach is capable of accurately capturing the variation law of harmonic loss in the operating distribution transformer, based on the harmonic number and harmonic distortion rate. Increasing the load side power factor and improving the three-phase load imbalance can effectively reduce the harmonic load loss of the distribution transformer. Nonlinear load unbalance mainly causes the increase of 3rd and 5th harmonic additional loss.