Transient Analysis for Over-Current of Electromagnetic PT due to Single-Phase-Grounded in Ungrounded Neutral System

In ungrounded neutral system the over-current in the primary of electromagnetic potential transformer (PT) due to single-phase-to-earth fault takes place frequently. This paper focuses on the transient analysis of the above over-current phenomenon. Base on the equivalent circuit and the electromagnetism character of PT, we deduce the transient equation of PT current and disclosure the essence reason of over current. With computer simulation (MATLAB) and experimental study in the laboratory (the 10kV high voltage physical simulating system) verified the precision of the analysis result in this paper.