Electrical Parameter's Change In Different Frequency Of Dry-Type Air-Core Reactor With Transposed Conductor Winding Short-Circuit

With the rapid development of power systems,the reactive power compensation capacity increases.Dry-type air core reactors are gradually moving toward large capacity and high voltage levels,and the volume is getting larger and larger.The single-layer wound dry type air core reactor has a complicated process,and the shortcircuit failure rate of the turn-to-turn is improved.In order to solve this problem,in recent years,transposition wire-wound dry-type air core reactors have been used.The frequency characteristics of impedance change after the short-circuit fault of the new type of dry-type air core reactor are studied,which provides a basis for the detection and monitoring method of the inter-turn short-circuit fault and the fault identification method.This paper proposes a calculation method for the equivalent resistance and equivalent inductance of dry-type air core reactors with the same strand and different strands,and prepares the matlab calculation program.On this basis,a BKDK-20000/35 dry-type air core reactor is taken as an example to calculate the frequency characteristics of the equivalent resistance and the equivalent inductance under different types of inter-turn short-circuit faults at different positions.A sample of transposed wire dry-type air core reactor was designed and fabricated,and different types of inter-turn short-circuit faults were simulated at different positions.A verification test was carried out under power frequency and high-frequency pulse oscillating voltage.The calculation results show that when the transposed conductor dry-type air core reactor has the same inter-turn-to-turn short circuit,the equivalent resistance increases,the equivalent inductance decreases,the amplitude reaches the same height position,and the equivalent inductance and the equivalent resistance change are all shortcircuited.The position changes gradually from the inner layer to the outer layer.In the same layer of the axial direction,the variation of the equivalent inductance and the equivalent resistance gradually increases from the end to the middle as the short-circuit position changes.As the frequency increases,the amount of change of each parameter increases obviously.When the frequency reaches a certain value,the amount of change of each parameter increases and is saturated,and does not increase with the increase of frequency.When the short circuit between different strands is short,the equivalent inductance and the equivalent resistance are basically unchanged at low frequencies.As the frequency increases,the equivalent inductance gradually decreases and the equivalent resistance gradually increases.At the same height position,the equivalent inductance and the equivalent resistance change gradually increase from the inner layer to the outer layer as the short circuit position changes.When the frequency reaches a certain value,the amount of change of each parameter increases saturates and does not increase with increasing frequency.The power frequency test and the high frequency pulse oscillation test result show that it is obviously easier to detect the inter-turn short circuit fault at high frequency,and the short-circuit faults of different strands that are difficult to find in the initial stage of the inter-turn short circuit can be effectively tested by the high-frequency pulse oscillation test.