Magnetic Field Analysis And Monitoring Method About The Failure Of Dry-type Air-core Reactor

The dry-type air-core shunt reactor is one of the principal reactive-load compensation equipment in the electrical power system.With the vigorous development of UHV power grids,a growing number of reactors are in operation.As for keeping the high quality transmission of electric energy and the safe operation of the power grid,it is critical to maintain the low failure rate and maintain the stable operation.At present,the dry-type air-core reactor occurs more turn-to-turn short circuit faults caused by different situations.As a result,burning accidents of the electric equipment are developed.In this time,there is no effective monitoring means of air-core reactor failure,so it is necessary to study the distribution characteristics of the dry-type air-core reactors in the normal state and fault state,and to propose an effective fault monitoring method.In this paper,a 66 kV side dry-type air-core reactor of the 500 kV substation is employed as an example.Magnetic field distribution of turn-to-turn short circuit is analyzed in detail by simulating its running state.Firstly,through the theoretical analysis of the analytical method and finite element method,the finite element method is used as the main analytical method.And then,the finite element model of the dry-type air-core reactor will be created by using the simulation software named Ansoft Maxwell.By calculating the magnetic induction intensity and current value under normal condition,we will compare the data with the analytic result,then the correctness of the model establishment can be verified.On this basis,the coil current and the magnetic induction intensity of the reactor when the turn-to-turn short circuit occurs at different positions of the reactor will be analyzed in detail.The result shows that the turn-to-turn short circuit will reduce the magnetic induction around the dry-type air-core reactor.In the same winding,the fault location appears at the center height and the weaken degree of the magnetic field is the greatest.As for the equivalent height,the fault location appears in the outermost winding and the weaken degree of the magnetic field is the greatest.Finally,depending on the result of magnetic field analysis,the method of using the induction coil to detect the change of the magnetic field around the dry-type air-core reactor is proposed.Through the analysis,it complies with the requirements to arrange the induction coil at the ground potential below each phase reactor.The monitoring coil of the each phase reactor is connected into the open delta connection.By monitoring the induction voltage changes in the opening,the operating state of the reactor can be controlled.At the same time,the feasibility of this method can be demonstrated by analyzing the working principle and the experimental data.The results of this paper can provide some theoretical bases and inspiration for the research of fault state of dry-type air-core reactors and the development of fault monitoring methods.