Research On Partial Discharge Detection And Location System For Switchgears

Switchgear cabinet as an important power equipment in the distribution network,its insulation defects in the production or operation process can easily lead to partial discharge,after a certain period,the short-gap partial discharge will cause long-gap breakdown,which can destroy the normal operation of the switchgear and bring huge economic losses.Therefore,it is effective to improve the stability of the power grid if it can detect the partial discharge of the switchgear normally and detect the hidden danger of the insulation in time.In this thesis,based on the advantages and disadvantages of various detection methods,the TEV method is used to detect the partial discharge of the switchgear,and the partial discharge source is accurately positioned by the HFCT and ultrasonic sensor.In view of the fact that some partial discharge detection devices at this stage have the characteristics of limitations of the sensor and the characteristics of the oscilloscope’s compatibility with the sensor,this thesis proposes collect partial discharge signal based on the serial port communication between the oscilloscope and the Lab VIEW,and designs detection and positioning device for the partial discharge.Firstly,this thesis discusses the causes and characteristics of typical partial discharge in the switchgear based on the theory of partial discharge.In this thesis,an electric field coupled TEV sensor is developed for the partial discharge generation mechanism and three kinds of partial discharge detection theories.The TEV sensor is validated that it has a wideband and high sensitivity under the laboratory condition.The similarity verification method is used to analyze the characteristics of the HFCT sensor.It is concluded that the effective frequency band of the HFCT sensor is much larger than the center frequency of the ultrasonic wave,so HFCT can detect high-frequency current signals that are rapidly propagating,that is,the validity of the joint method is verified.The finite element difference method(FDTD)is used to simulate the electromagnetic wave distribution and the induced voltage caused by partial discharge in the switchgear.The simulation results has a very important guiding significance for the experiment of partial discharge detection.Secondly,the LabVIEW completed software design for the partial discharge detection and positioning device.The core of the software program is:LabVIEW achieve the USB serial communication between oscilloscope and the host computer through the VISA connection,and real-time acquisition of two signals;the collection of TEV partial discharge signal is achieved digital filtering and wavelet noise reduction,analysis of a single discharge pulse waveform,single pulse spectrum and PRPD spectrum;write sound and electricity joint positioning program,extract the delay time for ultrasonic signal relative HFCT signal,embedded improved Levenberg-Marquardt(LM)algorithm to achieve positioning.Finally,under the condition of laboratory,the typical partial discharge model of the switchgear is designed and the test platform is built.The three kinds of partial discharge are analyzed by the detection device,and the corona discharge is precisely positioned.The results show that the partial discharge detection device of the switchgear can effectively identify the different discharge types in the experimental environment,and can achieve positioning accurately,so the detection device basically meet the design requirements and testing needs.