Research On Insulation Detection Technology Of Dry-type Voltage Transformer Based On Pulse Voltage Method

Dry-type voltage transformers are widely used in power systems due to their simple structure and easy maintenance.In recent years,faults have occurred frequently.The turn-to-turn insulation faults of the primary winding account for a high proportion,so the turn-to-turn insulation detection should be strengthened.Due to the serious deficiencies in the field turn-to-turn insulation test of dry-type voltage transformers,such as frequency doubling induction withstand voltage test,it is necessary to study the turn-to-turn insulation detection method that is convenient to carry out on site.Referring to the current detection methods of turn-to-turn insulation of coil equipment,this thesis tries to detect the turn-to-turn insulation of dry-type voltage transformer with pulse voltage method.The specific work is as follows:In order to study the relationship between the characterization parameters and the number of turns under the fault-free situation as well as the variation law between the characterization parameters and frequencies under faultless and fault conditions,the model specimens of the fault-free and fault are prepared.The defective model specimens have faults with different short-circuit turns and different short-circuit positions.At the same time,the test platform for the determination of the characterization parameters is built.The voltage,current,active power and reactive power of the model specimen at different frequencies are measured.The equivalent resistance,equivalent reactance and equivalent inductance are calculated.The relationship between the parameters and the number of turns under the fault-free situation is analyzed.The parameters include voltage,current,equivalent resistance and equivalent reactance.The variation law between the characterization parameters and frequencies is analyzed.The characterization parameters include equivalent resistance and equivalent inductance.This research provides theoretical support for the simulation of pulse voltage experiments for dry-type voltage transformer.In order to study the feasibility of detecting the turn-to-turn insulation of the primary winding of dry-type voltage transformer by pulse voltage method,the characterization parameters of the primary winding are calculated.At the same time,the pulse voltage test simulation circuit is established.The voltage waveforms at the end of the primary winding are obtained by simulation.The voltage waveform parameters are analyzed.The circuit component parameters are optimized.This research provides theoretical support for the application of pulse voltage method in turn-to-turn detection of dry-type voltage transformer.In order to verify the feasibility of detecting the turn-to-turn insulation of the primary winding of dry-type voltage transformer by pulse voltage method,the model samples of the primary winding with no fault and different short-circuit turns are made.At the same time,the pulse voltage test platform is built.The voltage waveforms at the end of the primary winding without fault and with different short-circuit turns are measured.The voltage waveform parameters are analyzed.This research provides support for the practical application of pulse voltage method in turn-to-turn detection of dry-type voltage transformer.The research results show that the parallel oscillating inductor can make the pulse voltage waveform oscillate and decay rapidly.The equivalent inductance under fault is lower than that without fault,and decays rapidly with increasing frequency.So that the oscillation frequency before and after the fault is different.Through the difference between the attenuation speed and the zero-crossing point of the pulse voltage waveform,the dry-type voltage transformer with turn-to-turn fault can be detected.The greater the number of short-circuit fault turns,the greater the oscillation frequency of the pulsed voltage waveform,and the longer the time for the pulsed voltage waveform to decay to zero.The research results of this thesis can provide a theoretical basis for the detection of turn-to-turn insulation fault of primary winding of dry-type voltage transformer by pulse voltage method,which is of great significance for the stable and safe operation of power systems.