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The method of fast non-destructive testing for aluminium sheaths of high-voltage (HV) cables using ultrasonic-guided waves is proposed. The dispersion curve is calculated by solving the dispersion equation from the simplified model of aluminium sheaths of HV cables; thus, the appropriate wave mode and excitation frequency can be chosen. Three defects including crack, perforation, and sag have been set up. Then, the simulation experiments have been carried out for aluminium sheaths of HV cables based on the theoretical analysis and finite element simulation. The results show that cracks with the loss ratio of the sectional area over 4.25% can be detected by the T (0, 1) mode whose frequency is 32 kHz; the amplitude of the flaw echo increases along with the loss ratio of the crack. Theoretical analysis, finite element simulation, and experiments prove the feasibility of aluminium sheaths using ultrasonic-guided waves, providing a new method for the defect testing.

In underground cable water tree is the main defect, of which discharge plays an important role in the aging process of insulating materials. To investigate the microscopic mechanism of water-tree discharge in underground cable, a numerical plasma-chemical model is developed. The dynamic characteristics of water-tree discharge are analyzed, including voltage waveform, current waveform, the electron density, electron temperature, ion density, electric field and electron capacitance power deposition. Our results reveal that these waveforms of current and voltage show periodic behaviors. As the increase of the formation of pulse current, the spatiotemporal distributions of electron density and ion density significantly increase, which change the electric field polarity in water tree. Meanwhile the distorted electric field becomes the energy source of electron avalanche and electron temperature. In addition, it was found that capacitive power dissipation gathered on dielectric surface, which aggravates the aging process of the insulation material.

this paper discusses research and trial application of mobile sensing and interactive diagnostic technology for power cable lines. The comprehensive construction of intelligent operation and maintenance system combined with the modern information technology, intelligent technology and the traditional technique is an urgent demand. The mobile sensing and interactive diagnostic technology for power cable lines integrates technique of conventional statue detecting, on-line monitoring, tunnel monitoring and patrol robot, supported by the internet of things technology and combined with RFID technology, individual mobile terminal technology, multiple states sensing technology, patrol robot technology, the distributed diagnosis technology and data interactive technology. The whole system makes operation staffs conveniently acquire operation indicators and preliminary analysis of power cables lines and tunnels in the process of patrol and maintenance, master and update real-time operational information of power cables lines and tunnels, such as operating state, fault prediction, risk level and maintenance recommendation by communicating with control center platform. Further application of the technology will innovate maintenance mode and promote intelligent level, efficiency and effects of operating management and maintenance of power cable lines comprehensively.