Research On Detection Technology Of Turn-to-turn Short Circuit Fault In Dry-type Air-core Reactor

In modern power systems,dry-type air-core reactors play a pivotal role,but with the investment of equipment,reactor accidents have gradually occurred frequently,and most of the faults are caused by short circuits between turns.At present,there are very few technical researches on reactor turn-to-turn short circuit fault detection.The existing methods are greatly affected by the natural environment and electrical environment,resulting in poor reliability,low accuracy,low sensitivity,and poor adaptability.Therefore,it is very important to research on the inter-turn short-circuit fault detection technology of dry-type air-core reactors.Firstly,this article first analyzes in detail and establishes a simplified equivalent model of dry-type air-core reactor during normal operation and short-circuit between turns,derives the calculation formulas of resistance and inductance,and obtains the current of each satellite arm.A method for detecting inter-turn short-circuit faults based on the current ratio of the star-arm and the star-arm of the reactor.Secondly,the calculation and analysis of 1,3,5,7,9,11,13 encapsulating the typical type of reactor in the normal and turn-to-turn short-circuit the size of the current ratio of the star frame arm current ratio distribution law: The current of the fault layer winding increases and has the largest amplitude.During normal operation,the change rate M of the current ratio of the reactor star frame arm at any time is almost zero;As the number of encapsulations increases,the minimum rate of change of the star arm current ratio appears when the first encapsulation internal winding turns short circuit;when there is a short circuit between turns,the sensitivity of the rate of change of the star frame arm current ratio at the minimum and maximum is about 81 and 27 of the sensitivity of the total current rate of change.The sensitivity of the star arm current ratio before and after the fault is higher than that of the total current change rate.Furthermore,the fault criterion of the turn-to-turn short circuit is summarized: When the star arm current ratio change rate M is greater than or equal to 4.849%,it is considered that an inter-turn short circuit has occurred.Finally,taking 13 encapsulated reactors as an example,Simulink modeling and simulation were carried out.By comparing the output results of the short circuit signal before and after the t=0.4s fault and t=0.2s before and after the voltage fluctuation,the results presented in this paper were verified The accuracy and sensitivity of the inter-turn short-circuit fault criterion has a certain margin.After that,the "test reactor" was tested for the inter-turn short circuit when the current of 10 A and 15 A was pressurized in the laboratory environment,and the test of the pressurized 2kV inter-turn short circuit in the reactor workshop.The actual measurement results show that the fault criteria can be accurate and sensitively reflect the fault of the turn-to-turn short circuit.