Development Of Inter-Turn Insulation Test Device For Air-Core Reactor Based On Impulse Oscillating Method

The air-core reactor is mainly used in the power system to suppress the rise of the power frequency voltage,limit the short-circuit current and reduce the influence of harmonics in the UHVDC transmission.The inter-turn short-circuit fault caused by the inter-turn insulation defect during operation is the main fault form of the air-core power reactor.In order to effectively detect the turn insulation state of the air-core reactor in operation and avoid accidents,it is very necessary to develop a device that can regularly check the turn-insulation of the air-core reactor in service.In order to study the change rule of the pulse oscillation waveform when the air-core reactor occurs in the inter-turn short circuit at different positions,firstly,according to the equivalent circuit model of the air-core reactor when the inter-turn short circuit occurs,the parameters of the inter-turn short circuit at different positions are calculated,which is the pulse oscillation method.The equivalent parameters of the hollow core reactor in the simulation analysis provide corresponding data.Then,according to the experimental schematic diagram,the relationship between the oscillation frequency and attenuation factor in the pulse oscillation wave and the equivalent resistance,inductance and capacitance is analyzed and obtained,and the change rate of the oscillation frequency and the attenuation factor is used as the positioning criterion.Finally,the Simulink simulation software is used to simulate the inter-turn short circuit of the air-core reactor at the end and the middle.The magnitude of the rate of change can distinguish different fault locations.In order to reduce the size of the equipment to facilitate on-site testing,the device developed in this thesis to detect the insulation of the air-core reactor turns,and a Cuk conversion circuit with small output voltage ripple is designed.The inverter circuit is designed to output 400 Hz sinusoidal voltage,and the duty cycle is controllable,which can flexibly adjust the charging and discharging time during the test process,and the inverter circuit adopts double closed-loop control,which can effectively improve the dynamic response of the output voltage and suppress excessive Zero spikes.A resistive voltage divider for measuring DC high voltage and a resistive-capacitive voltage divider for measuring pulse oscillation voltage are designed,which can meet the acquisition of the highest peak voltage.And also developed a set of host computer software control system,its development platform is Lab VIEW software,using MODBUS communication protocol to realize the communication between the host computer and DSP,which has certain practical significance in engineering.In this thesis,the completed turn insulation testing equipment is used to conduct the inter-turn short circuit test on the air-core reactor,and simulate the single-turn short circuit of the upper,middle and lower parts of the air-core reactor and the upper middle,upper and lower,middle and lower double-turn short circuit,a total of six In this case,it can be concluded that the change rate of oscillation frequency and attenuation factor is larger in the middle inter-turn short circuit than the upper and lower inter-turn short circuit,and the change rate of oscillation frequency and attenuation factor is larger in double-turn short circuit than single-turn short circuit.