Design Of Partial Discharge Detection System In Power Transformer Based On ARM

Partial discharge (PD) in power transformer gives primary cause for transformer breakdown. The principal mean of examining power transformer movement status is judgment transformer insulation ability through detecting the character of PD signal. Ultrasonic detection is one of PD detection. The structure\performance\function of ultrasonic detection system is limited greatly because of their MPU with storage space, running rate and low integration rate etc. Because ARM MPU is provide with the performance of high-frequency, multi-purpose, low power and low cost, the plan that S3C2410s andμC/OS-II is applied to the design of partial discharge detection system in power transformer is proposed. Acquiring and analyzing the partial discharge ultrasonic signal. This system realizes the detection function through acquiring and analyzing the PD ultrasonic signal basically. Compared with the detection system with other MPU, it is provide with the excellence of high speed, simple structure, convenient for carry etc.The analog signal pretreatment circuit is designed, which is constituted of third-level amplifying circuit and butterworth bandpass filter with 80 to 300KHZ. They can adjustment peak-to-peak value to request scope of A/D input signal scope, and suppress massive low frequency and the high frequency cycle unwanted signal. The functional modules of signal acquirement, graphical display, correspondence, keyboard control and data storage are designed based on the multi-control interfaces of S3C2410s. The application software of frequency analysis, digital filter and wavelet denoise and the driver of various function modules is designed based on the high speed of S3C2410s andμC/OS-II.This system is tested with the analog signal of PD ultrasonic which is from arbitrary signal generator and added to high frequency, low-frequency cycle disturbance and white noise. The results show that the filter circuit can suppress and attenuate massive low frequency and high frequency cycle unwanted signal in excess of 80 to 300KHZ; the amplifier can adjustment peak-to-peak value to request scope of A/D input signal scope; the application software of frequency analysis, digital filter and wavelet denoise can qualitatively analyze the size, the triggering time, frequency characteristic of primary signal. According to these signal characteristics, the system can qualitatively judge whether PD happens and its size; the further research on PD type and discharge source position can be realized. Thus it can be seen that the design of hardware and software can be use to on-line detect the partial discharge ultrasonic signal and provide accurate reliable information for judging the PD status.