Electromagnetic Compatibility Study On Electronic Instrument Transformers In Smart Substations

Benefited from the incorporation of smart grid into China's national energy strategy, the development of smart substation has accelerated into the fast lane. Electronic instrument transformers, serving as the link between primary-side and secondary-side equipment, provide primary-side current and voltage values to electronic devices installed at secondary-side. As these transformers contain microchips that are susceptible to electromagnetic disturbances, they fail to function every now and then. It becomes imperative to find out troubles that greet electronic instrument transformers caused by EMDs and to design electromagnetic compatibility measures.After study on IEC 60044 and IEC 61850, the author takes a part in designing the MSP430-based collector and ARM9-based merging unit. To determine the characteristic amplitudes and frequencies of the major electromagnetic disturbances in substations which are vital in designing EMC measures, this paper tracks down the electronic instrument transformers' on-site problems and their causes. Special attention to VFTO in GIS and the EMD induced thereby is also paid in this paper.The author continues to analyze the influence on accuracy of measuring imposed on sensors and microchips by EMDs and looks into these disturbances' coupling paths. The paper then designs circuits that are capable of filtering the major EMDs in substations. Compared with EMC measures generally adopted by the power industry, the filter would better suppress the major EMDs, especially those disturbances spawned by VFTO.This paper concludes with some type tests to electronic instrument transformers. And the test results show the reasonability of filter design.