Transformer Winding Deformation Detection System Based On Ultrasonic Coding

Winding fault is the main hidden danger threatening the normal operation of transformer.It is of great significance to locate and analyze the winding fault position accurately and reliably.Ultrasonic detection has been applied in the field of winding detection because of its advantages of intuitionistic,quantitative and no electrical connection with transformer,but it has some defects such as low accuracy and low detection efficiency.Therefore,in this paper,pulse coding technology is applied to ultrasonic detection,and a transformer winding deformation detection system based on ultrasonic coding is designed.The system can detect the transformer winding accurately,intuitively and efficiently.First of all,based on the propagation path of ultrasonic wave in transformer box,this paper analyzes the energy loss and wave type conversion of ultrasonic wave in steel medium and oil medium of transformer shell,and puts forward the joint detection method of longitudinal wave probe,transverse wave probe and angle probe.According to the position of transmitting probe on the outer surface of transformer and the law of ultrasonic reflection,this paper formulates Probe placement strategy is proposed.On this basis,the algorithm of three-dimensional position point conversion of winding is proposed.The three-dimensional coordinate points of winding are calculated by three-dimensional position of transmitting probe,three-dimensional position of receiving probe and ultrasonic time delay value.Probe placement strategy and three-dimensional position transformation algorithm are the basis of the whole ultrasonic detection of transformer winding.Secondly,this paper analyzes the M-sequence,Gold sequence,Barker sequence and L-sequence,and selects Barker sequence and Gold sequence as the main coding sequence,taking autocorrelation and cross-correlation as the evaluation index,starting from the depth and accuracy of ultrasonic detection,and then analyzes the amplitude shift keying,frequency shift keying and phase shift keying The modulation mode is evaluated.The excitation energy and energy efficiency are taken as the measurement indexes,and the frequency shift keying is chosen as the main modulation mode.On this basis,the time delay of ultrasound can be calculated accurately by using the generalized cross-correlation algorithm as the pulse compression method,which greatly improves the efficiency and accuracy of ultrasonic detection.Finally,this paper designs the hardware and software system of transformer winding detection based on ultrasonic coding.In the hardware system,according to the selected ultrasonic transducer,the high-voltage excitation generation circuit,echo processing circuit and data acquisition module are designed to form the whole ultrasonic code detection system.The system can transmit multi-channel ultrasonic signals with different coding excitation at the same time,detect the transformer winding,and upload multi-channel transmitted wave data and echo data to the upper computer.In the software system,the collected waveform data can be pulse compressed to calculate the time delay value of ultrasonic propagation,combined with the three-dimensional position of the probe to calculate the three-dimensional coordinates of the winding.The system can quickly generate the three-dimensional diagram of the winding surface,and get the unfolded diagram of the winding surface,which can directly see the winding deformation position and deformation amount.Finally,the system is applied to the detection of transformer model,and good results are obtained in the laboratory.The experimental results show that the system can detect the state of transformer winding intuitively,quantitatively and efficiently.