Research On The Electromagnetic Transient Process In Distribution Network Switchgear And Its Influence On EVT

With the vigorous promotion of the distribution of equipment and the development of intelligent and integrated switchgear,the electronic instrument transformers work in a complex electromagnetic environment,their signal processing part such as the collector works close to the primary side.The transient process caused by the switching operation of the primary side is easily transmitted to the electronic circuit part of the transformer,so that the electromagnetic interference frequently occurs to the electronic instrument transformers.At the same time,the high frequency interference carried by the switching operation also affects the measurement characteristics of the electronic instrument transformer,causing the distortion of the collector data and the protection malfunction.The influence of a transient interference on electronic instrument transformers cannot be ignored anymore.Therefore,it is necessary to research on the impact of transient interference on the electronic instrument transformers,which can provide the theoretical basis and practical engineering application value for the optimization of its transient response characteristics and promote the integration of distribution networks.In this thesis,for the electronic voltage transformer in the 10 kV switchgear,the switch re-ignition model is established.The generation mechanism and time-frequency characteristics of the switch operation over-voltage in the switchgear are researched.Under the over-voltage conduction interference,the transient response characteristics of electronic instrument transformers are analyzed.Influencing factors on high frequency transmission characteristics of electronic instrument transformers are analyzed.It is found that the re-ignition of the switch will generate high-frequency components,affecting the voltage divider characteristics of the electronic instrument transformer,and cause damage to the collector.A 10 kV electromagnetic interference detection platform of the electronic instrument transformer under AIS switch operation is built.The actual response of the electronic voltage transformer is tested,it is found that the operation over-voltage amplitude is not more than 3 times p.u.,lasting 20ms~60ms,and the high frequency is mainly distributed in 2MHz~5MHz.It is necessary to add filtering measures before the collector.The research results can provide theoretical basis and technical support for the transient performance optimization of electronic instrunment transformers,which can further improve the long-term operational stability of electronic instrunment transformers,and provide experiment for the improvement of electronic voltage transformers transient performance test.