Analysis Of The Errors In Lightning Event Counters And Research On Identification Of Effective Triggering Count Signal

Lightning Event Counters(LECs) have provided an intuitionistic and reliable on-line method for the evaluation of protection efficacy about lightning protection devices. They not only support data to analyse disaster causation of electric transmission line for power plants, but also afford coherent units with scientific basis to reach the optimal design of lightning protection system. Accurate counting is the basis of achieving all these functions, and the accuracy of counting is the most important performance index of LECs, undoubtedly, it has been an important research field to improve the counting accuracy.An in-depth research to analyze the error-source during the process of triggering counting signal about LECs based on circuit construction and operational principle is presented to deal with the problem that LECs usually register with high records. Then we classify the errors into two groups, output characteristic of sensor and electric current model selecting, to investigate formation mechanism and suppression measure of counting error. According to study on causation of waveform distortion and influence to count result after packaging current transformer with outer metal shielding layer, control methods is shown to tackle output distortion of sensor. The proposal that threshold current should be1,000A to avoid interference caused by continuous current and low-current-peak M component is provided based on the relationship between various physical property discharge pulses in a real cloud-to-ground lightning flash and triggering-count signal. Then a notion that count-pseudoinstructions fail to recognize, which produced by high-current-peak M component and multiple oscillation during one return stroke, are the main factors leading to count error is proposed.Through vast comparative analysis on measuring data of triggered and natural lightning flashes, characteristic parameters as return stroke wave-head gradient, effective pulse length and effective pulse duration are extracted and valid trigger count signal pick up circuit is developed. Since gradient detection method can distinguish return stroke that meeting judging condition, the monostable flip-flops generates only count within one return stroke symbol period. Circuit simulation shows that the above methods can restrain the noises of high-current-peak M component and redundancy signals created by multiple oscillation during one return stroke, also enable LECs to improve valid triggering-count signal identification precision.