Research On Online Partial Discharge Monitoring For Distribution Underground Cable Joint

With the rapid development of the domestic economy,the electric load of the power grid is increasing,and the XLPE power cable is used in transmission and distribution network because of its superior performance.With the continuous extension of the cable,cable joint use volume also gradually increased,and cable joint structure is by multi-layer composite material of closed type solid insulation,so its insulating properties are easily influenced by the many aspects,safety margin is small,resulting in the cable body more prone to failure.According to the characteristics of the cable joint and the real-time operation condition of the cable insulation,the condition of the insulation of the cable connection must be monitored and evaluated on line.In this paper,firstly,the existing power cable online monitoring methods of are analyzed and compared.It is pointed out that the advantages and disadvantages of them,summarizes the domestic and foreign XLPE cable joints insulation detection technology research status and analysis of the cable joint bureau put a difficult point in the study of on-line monitoring,and puts forward a method of insulation condition assessment of cable joints.The transmission characteristics of cable partial discharge signal and the suppression of disturb in online cable is studied also.According to the fault of the cable joint,the paper puts forward a method to diagnose the insulation condition of the cable connection by using the partial discharge signal.According to the random nature of partial discharge,the collected signal data are made into normal distribution mathematical model to analyze the data.When the cable fault occurs,the parameters of the model consequent changes in the larger,through its standard poor confidence level to identify outliers and outlier appear said insulation situation began to change change greatly,through the simulation of cable joint fault experiments,the obtained signal analysis,identify outliers interval,determine the cable insulation condition.In the end,the on-line insulation monitoring system of XLPE cable is designed.Through current and voltage sensors,the acquisition of the discharge signal afteramplifying and filtering a series of transmission to the monitoring unit.Finally after internal units of the digital to analog conversion income data signal is transmitted to DSP,DSP processing digital signal transmission to the remote computer for next step processing,according to the actually reflects the situation to judge the insulation condition of the cable joint,real-time monitoring of cable joint,improve the safety and stability of the power cable operation.