Study On Chaotic Detecion Method For Cable’s Partial Discharge

Cross-linked polyethylene (XLPE) cables are widely used in electric power systems. XLPE cables in the long running process, due to the effects of stress and environmental factors, inevitably there will be some insulation defects, the insulation fault have occurred. Currently XLPE cable water tree and the electric tree discharge phenomenon are objectively existed, which has cable insulation accelerated aging. Power sector need the effective method urgently to detect the cable insulation defects, judge the insulation aging state and evaluate insulation life. In recent years of research indicates that, partial discharge detection is effective method, but due to the particular cable structure, partial discharge pulse transmitting in cable exists high frequency attenuation, and waveform distortion etc. problem, coupled with electromagnetic interference, Discharge pulse signal reaches the sensor may be weak, the detection sensitivity must be enhanced to detect partial discharge pulse signals effectively. In addition, partial discharge pulse transmitting along the cable have severe attenuation distortion, which affect the insulation ageing state characteristics, and the cable insulation ageing diagnosis. Study on response to these two issues in this article.To improve the PD detection sensitivity, we use the coupled Duffing oscillator to detect PD pulse for XLPE cable, which is very sensitive to the pulse excitation, and immunity to the white noise. According to the PD time domain and frequency domain characteristics, the especially coupled Duffing oscillator model for the cable’s partial discharge detection be constructed, include the coupling coefficient of the coupled Duffing oscillator, the period and amplitude of the periodic driving force and initial value. Calculating the maximum transverse Lyapunov exponents of double coupled oscillators to judge synchronization between the oscillators, using the synchronization error of the coupled Duffing oscillators to detect PD pulse signal. The simulation and experimental results show that the processing method, based on the transient synchronization mutation phenomenon of the coupled Duffing oscillator system, can effectively suppress the white noise and detect the weak PD pulses and the PD pulse detection sensitivity is improved greatly.The effect of XLPE cable high frequency loss on the PD characteristic parameters which token the insulation aging condition are investigated in this article on the basis of existing studies. On the Matlab-Simulink simulation platform, XLPE cable distributed parameter model is established. Adopt the tip-plate electrode discharge to simulate the cable partial discharge. This discharge signal is used to input signal to, then simulate the PD chaotic characteristic parameters change with the different range. Got the laws of chaos characteristic parameter varies under the relatively short range, with the transmitting range increases, maximum Lyapnove index increased slightly, while the correlation dimension,k-entropy decreases. When the range is large, the spread in200meters, calculated the best delay and phase space embedding dimension jumped, while maximum Lyapnove index, correlation dimension will remain basically unchanged, while k-entropy change is not obvious.10kV XLPE cable discharge signal transmission experiments, experimental results confirm the chaos characteristic parameter variation law. Research results can be used for XLPE cable partial discharge monitoring and insulation aging diagnosis.