Design And Experimental Study Of UHF Partial Discharge Sensor For Power Cable

Partial discharge(PD)is the main factor that leads to the damage of power cable insulation.During the manufacturing process of cable or the installation of cable accessories on site,partial defects are easy to occur,which will cause tree like aging in the insulation of power cable,and with the appearance of partial discharge,the development of partial discharge will eventually lead to the breakdown of power cable insulation.The outstanding advantage of UHF detection is its strong anti-interference ability.The application of UHF method in PD detection of power cable still needs deep research in UHF electromagnetic wave propagation characteristics,sensor technology,UHF signal acquisition technology and PD characteristics under AC voltage.For this reason,the research on UHF detection sensor of PD in power cable is carried out in this thesis.The paper includes the following main contents:(1)The process of partial discharge is introduced and the harm of partial discharge to power equipment is also described.The importance of PD detection for power cable is realized,and the development process of power cable is understood.The generation and radiation characteristics of UHF PD signal are analyzed,and the theory of electromagnetic wave propagation in power cable is also analyzed.(2)The log periodic antenna model is established and simulated by HFSS software.The SWR of the corresponding log periodic antenna is obtained by changing the feed point position,the thickness of the dielectric substrate,the attachment material and other parameters.When the feed point position is L=323 mm,the thickness of the substrate is 1.0 When the material is copper,the standing wave ratio of log periodic antenna with this parameter is the smallest,and the LPA with this dimension is designed and manufactured(3)By changing the values of R and C and comparing them,it is concluded that when C = 0.01 NF,R= 10 k?,the effect of envelope is the best.When the input frequency of the double voltage detection circuit is increased from 300 MHz to 1000 MHz,the effect of the envelope curve will not change.The envelope detection system of UHF signal is designed.The distortion of sinusoidal response waveform is very small,the deviation between output frequency and theoretical value is very small,but the amplitude is lower than the theoretical value.(4)The log periodic antenna is used to detect the partial discharge signal generated under the typical insulation defect model.By comparing with the third-order Peano fractal antenna,it is verified that the log periodic antenna can meet the requirements of the partial discharge detection of power cable.When the log periodic antenna and envelope detector are used to detect the positive half cycle discharge,the number of times is the most,and the signal amplitude is large,The collected discharge signal is better than the other two antennas.