High Voltage Transmission Line Lightning Fault Diagnosis And Identification

The domestic and external operating experience we have collected and analyzedover the years, shows that influenced by the longer transmission distance andcomplicated landform factors and the climate conditions , 40 to 70% faults of HighVoltage Transmission Line was caused by lightning. The influence of lightning onTransmission Line can be divided into two main kinds: induction thunder andlightning. Induction thunder is overvoltage caused by static induction andelectromagnetic induction, due to its small amplitude value, only influencesTransmission Line with poor dielectric strength, such as 35kV Distribution Network.During the discharge process of lighting, there are very high current and voltage,which direct effect on poles and towers of transmission line, will bring aboutenormous damage. Then line insulation was broken down, earthing fault occurred, andthere will be massive defaults in substation or client-side. While the high frequencyinterferential signal can severely interfere with equipments along the line. Theresearch on fault of high voltage transmission line should focused on lightning.According to the domestic and external operating experience, the influence oflightning on Transmission Line can be divided into two main kinds: counterattack anddetour lightning. When counterattack occurred, thunder and light do not act onTransmission Line directly, but go straight to poles and towers or overhead groundwire. The existence of grounding resistance makes the top of the towers get highpotential; induction voltage is generated in transmission line by electromagneticinduction. When the potential difference across its terminals reaches flashover voltage,insulator was broken down, and the transmission line is tripped off. This is what wemean by counterattack. It is shown that due to limitations of the shielding action,thunder and light rounded overhead ground wire directly inhibited transmission lineand made it gain high potential and current. Then insulator was broken down, and thetransmission line is tripped off. This is what we mean by detour lightning. Thedifferent fault mechanism of detour lightning and counterattack result in diverseinfluence on protective measures. According to practical experience, it would bedifficult to find the difference between the two fault mechanisms. So we need a morescientific and more efficient discrimination mode.In this paper, an emulational model has been set, using ATP, and two sets of faultparameters and images are obtained. By analysis, possessing the characteristics of two different fault dates, we can identify the two fault mode superficially. Thentransacting the date and images with MATLAB essentially, the simulation resultsshow the amplitude and phase frequency range, power and energy range . The papermainly adopt FFT transform and wavelet packet analysis based on MATLAB toanalyze data obtained by ATP simulation.