PD Positioning Method and Experimental Study Based on Circular-shaped Ultrasonic Array Sensors

PD ultrasound array positioning method is one of the latest achievements in the field of array sensor technology and array signal processing technology. This method can achieve spatial orientation and on-line monitoring of partial discharge source effectively. Ultrasonic array sensor was developed rapidly in the past forty years, its application involves many areas of military and national such as radar, exploration, sonar, communications, seismology, radio astronomy, biomedical engineering, etc. Previous studies showed that the positioning performance of circular-shaped array sensor is superior to the square, linear array sensor and other forms. Therefore, we undertook in-depth study in allusion to circular-shaped ultrasonic array sensor. Contents of this paper are summed up in the following three aspects. Firstly, this paper developed a circular-shaped ultrasonic array sensor. We carried out a detailed and comprehensive investigation on structures, materials and size parameters of array sensor elements and assemblies, and we combined with the specific characteristics of PD ultrasound signals, then we determine the structure of array sensor elements and its main parameters: the dimensions of probe and tail are Phi 7.8x13mm Phi 5.2x13mm, the frequency range is 70kHz-280kHz, etc. The assembly is made of aviation aluminum materials, its sizes are as follows: length is 50mm, width is 40mm, the cylindrical bores in circular-shaped ultrasonic array sensor assemblies are arranged in a circular ring shape, the diameter of the cylindrical bore is 5.2mm, and the depth of the cylindrical bore is 5mm. We get circular-shaped ultrasonic array sensor by assembling ultrasonic array sensor elements and array sensor assembly. Secondly, since the actual PD ultrasonic signals from electrical equipments are wideband signals, we adopt rotational signal subspace (RSS) algorithm to focus processing, which can reserve the information maximally to realize the direction information accumulation of wideband signals. Use multiple signal classification (MUSIC) to realize DOA estimation of PD broadband ultrasonic array signals, its principle is to use the orthogonal characteristics of signal subspace and noise subspace. Then we adopt a kind of three-platform algorithm to locate the PD source. Lastly, we built a set up of PD ultrasonic array positioning system, which can realize reception, acquisition and processing of PD ultrasonic signals. This PD positioning system consists of partial discharge simulation system, signal reception and transmission system, multi-channel data synchronous acquisition and processing system, and computers. With this set of PD ultrasonic array positioning system we carried out experimental studies, we collected experimental data by changing the positions of partial discharge source and the circular-shaped ultrasonic array sensors, the results show that the positioning error is less than 8cm. The experimental studies showed that the PD positioning experimental system based on circular-shaped ultrasonic array sensor and the positioning algorithm are effective to locate PD source and can meet project needs, and lay the foundation for the practical application of engineering.