Analysis of Calculation of Artificial Neutral Point Resistance for Open-circuit Testing

Abstract

This article focuses on the artificial neutral point device with ZN connection (ZN type connection refers to the way that the primary winding adopts a zigzag connection and the neutral point is led out). In the process of breaking test, the arc energy is an important criterion. For three-phase four-wire transformers, the test loop can be built by connecting the N-pole with a pure resistance. However, for three-phase transformers, the loop needs to be built through the artificial neutral point. By analyzing the calculation and actual test data, the calculation method for the artificial neutral point resistance used in the experiment is clarified. It is confirmed that the resistance of the artificial neutral point will not change with the change of input voltage, making the calculation of expected fault current more accurate in daily use.