Research On Monitoring Method Of Inter-turn Short Circuit Fault Of Dry-type Air-core Reactor Based On Detecting Coil Method

Dry-type air-core reactors(DAR)are widely used in power grid reactive power compensation,filtering,and current limiting thanks to their high linearity,light reactors,low noise,ease of installation,and ease of maintenance.However,with the large number of DAR put into operation,there have been more burning accidents.According to statistical analysis,most of the accidents are caused by inter-turn short circuit,so it is very necessary to monitor the fault of inter-turn short circuit.However,most of the existing monitoring methods install the monitoring device on the DAR,which is inconvenient to install and maintain,and may affect the operation of the DAR.In this thesis,a non-contact monitoring method for inter-turn short circuit fault of dry-type air-core reactor is proposed by improving detection coil method.In this thesis,the simplified equivalent circuit model of DAR is constructed,and the electrical parameters of DAR are analyzed.The calculation method of branch current of DAR in normal state and inter-turn short circuit state between turns is given.Based on the variation of electromagnetic parameters of DAR when inter-turn short circuit occurs,the principle of monitoring method proposed in this thesis is explained,and the method of locating inter-turn short circuit fault is designed.At the same time,the calculation formula of induced voltage on detecting coil is deduced by calculating principle of induced voltage,and the calculation method of related parameters is introduced.In order to facilitate the design of detection coil,the formula for calculating the assumed value of DAR branch current and turns is derived when the current and turns are unknown.Secondly,Ansoft Maxwell simulation software was used to establish a simulation model of the normal operation state of DAR and the inter-turn short circuit state with reference to the parameters of a 35 k V reactor,and the variation law of branch current and short circuit current was summarized through the analysis of the simulation results.The coupling model between a single probe coil and DAR was established based on the DAR simulation model,and the variation rule of the parameters of a single probe coil and its induced voltage was explored.The parameters of several detection coils are designed according to the changing law,and the coupling model of multiple detection coils and DAR is established.Through simulation analysis,the variation law of induced voltage on the detection coil of DAR under normal conditions and when inter-turn short circuit occurs at different positions of DAR was demonstrated.The feasibility of monitoring the operating status of DAR through induced voltage was demonstrated,and the theoretical feasibility of the inter-turn short circuit fault location method was demonstrated by using simulation values instead of measured values.Finally,a hardware device for collecting induced voltage was manufactured,and a validation experiment was conducted on an 11 k V DAR in the factory,proving that monitoring the inter-turn short circuit fault of the DAR through induced voltage is feasible.