A ratio variation of equivalent instantaneous inductance based method to identify magnetizing inrush in transformers

Abstract

In terms of the characteristic of instantaneous magnetizing inductance reflecting the saturation stage in transformer, an improved method is proposed to distinguish between the magnetizing inrush current and short-circuit fault based on the ratio of average equivalent instantaneous inductances between the non-saturation and the saturation zone, which are divided according to a threshold of differential current. During the inrush, the value of equivalent instantaneous inductance varies severely from small to large as the transformer entering into the saturation and withdrawing from it, so the ratio of average equivalent instantaneous inductances between the non-saturation and the saturation zone is very large in one cycle. However, for the short-circuit fault in transformer, the equivalent instantaneous inductance is very small, and keeps little variation, so the ratio is approximately equal to one. The principle and setting of this method is simple and easy, and its identification time is short. The experimental results verify that the method is correct and effective.

A new model to study ultra-saturation phenomenon during the energization of a loaded three-phase power transformer and its effects on differential protection

“…To distinguish between inrush currents and internal faults in , the information of iron losses and the B–H curve are not required. In , equivalent instantaneous inductance is used to identify the inrush current. But none of these studies have modeled the ultra‐saturation phenomenon.…”

“…To distinguish between inrush currents and internal faults in [31], the information of iron losses and the B-H curve are not required. In [32,33], equivalent instantaneous inductance is used to identify the inrush current. But none of these studies have modeled the ultra-saturation phenomenon.In [3][4][5], the mal-operation of the differential protection during the energization of a loaded power transformer, whose extraction is known as an ultra-saturation phenomenon, was reported.…”

Control of unusual mal-operation of three-phase power transformer differential protection due to ultra saturation phenomenon based on Clarke׳s Transform and Discrete Wavelet Transform

“…To distinguish between the inrush current and the internal faults in [31], the information of iron losses and B-H curve are not required. In [32,33], Equivalent instantaneous inductance was used to identify the inrush current. In [34][35][36][37][38][39][40], the wavelet transform technique and fuzzy approach were used distinguish between the internal faults and the inrush current.…”