Partial Discharge On-line Monitoring For Termination Of Oil-filled Cable Based On Acoustic Emission Technology

The 500 kV submarine self-contained fluid filled cable is used in South China & Hainan Island Power Grid Interconnection Project. This is the first ultra-high voltage, long distance, and large capacity cross-sea power grid project of China. As the electrical stress distribution of cable termination is very complicated, the electrical stress components of tangential direction at interfaces between gas and solid, liquid and solid will cause partial discharges, therefore termination is the weak point of power transmission lines. But up to now there is no on-line monitoring system to insure the reliability of power transmission system on the line. So it is important to develop correlative measurement technology.The classic theory of PD and the micro procedure of generation of acoustic wave produced by PD are presented in this dissertation. During the generation of PD, the gas bubble will expansive and reduce. The ultrasound wave will be generated outside the gas bubble during this procedure.The application of ultrasound detection of PD in cable determination can effectively avoid electromagnetic interference and do not need to cut off power. So it is easy to realize the on-line monitoring. This article develops two on-line monitoring systems based on LabVIEW platform:the single-channel ultrasound on-line PD monitoring system and multi-channel ultrasound on-line PD monitoring system. The single-channel system which has the functions of signal acquisition, time domain analysis, frequency domain analysis, wavelet analysis, waveform storage, waveform display,2D chart display,3D chart display and report generation is appropriate for application in laboratory. The multi-channel system is appropriate for on-line monitoring including program of server and client. The program of server which is used to acquire and process signal of spot also has the function to transmit result through Ethernet. The program of client is used to read results from Ethernet and display it. The program which has the high automation and reliability and do not need to operate by man.The single-channel and multi-channel on-line PD detection system have been applied in the laboratory research. In order to simulate the defect in the operating cable termination, the needle-plane model, cavity discharge model, floating discharge model, surface discharge model and sliding discharge model are designed. By applying FFT and four parameters to the signal, the classification of different types of discharge model can be realized.