Research On Dielectric Loss Online Monitoring System Design And Related Questions

Capacitive devices' dielectric loss factor(tan ?)is an important indicator which reflects the high voltage electrical equipments'insulation performance, the overall defects or large concentration of local defects of the electrical equipments'insulation system can be found by measuring tan ?.For the dielectric loss's measurement accuracy is not high,the article proposed and designed a complete dielectric loss online monitoring system, including the design of the sensor, sampling systems, communication systems and PC processing system. And the dielectric loss's algorithms were compared and proposed, a new filtering algorithm based on correlation analysis was proposed to improve the measuring accuracy of dielectric loss online monitoring.After introduced the basic principle of capacitive substation equipments'measurement of dielectric loss?dielectric loss measurement's method and current research related presentations were based on the analysis and design of the overall framework of the dielectric loss line detection system. Systems based on the relative comparison method, the key lies in the accurate measurement of small currents, this article focuses on the current sensor and the corresponding filter circuit, through modeling and simulation, detailed examination of the relevant characteristics of the sensor to verify the feasibility of the system.On the basis of simulation, this paper complete substation equipment designed capacitive dielectric loss online monitoring system. Including signal conditioning circuits systems, sampling module and serial communication module controlled by a digital signal processor TMS320F2812, GRPS communication system and PC systems. Leakage current signal was obtained through the sensor, after the signal conditioning circuit conditioning filter,the signal was sampled by the AD, and then the digital signal was sampled through the GPRS wireless transmission module to the host computer and follow-up processing, display processing results and fault diagnosis in order to build a complete set of dielectric loss online monitoring system.Sampled leakage current signal contains harmonic interference and environmental interference, affect the measurement results. Based on the analysis of filter characteristics of the relevant proposed a new filtering algorithm for filtering harmonic interference and environment interference:the leakage current signal to two devices, respectively associated with the fundamental standards, a filtering process, and then filtered determined the relative dielectric loss between the two signals. On the basis of the new filtering algorithm, comparative analysed relatively comparison law and bipolar zero-crossing comparison law combined the new filtering algorithm's treatment effect. Experimental results showed that the combination of new filtering algorithm is feasible, relatively strong anti-interference ability, with high accuracy, whether it is to increase the harmonic interference or environmental interference, even if the algorithm in the case of signal to noise ratio as low as 10 dB can be accurately calculated, it will be valuable.