Study On Partial Discharge Location In Transformer Based On Ultrasonic Method

With the rapid development of economy, society is increasingly demanding for electric power, meanwhile, the safety and reliability of power equipment is getting recognized by electricity department. As the core of power equipment, if the power transformer breaks down, it can lead to a wide range of power outage, which will cause a heavy loss to people’s production and living. A study found that the degradation of insulation is the direct cause of transformer’s failure, and the partial discharge of transformer is the most essential cause. Therefore, the monitoring and locating of partial discharge plays an important role in preventing the premature damage of transformer, and becomes the primary task of the daily maintenance and fault diagnosis of transformer.There are a number of techniques to detect and locate the partial discharge in transformer at present. Among these solutions, the ultrasonic method is the main way for partial discharge in transformer because of its convenience and high precision. But the sensitivity of the existing solutions for detecting the ultrasonic signals is not high, and it could not locate object accurately. To solve these problems, this thesis will design a brand-new positioning system to locate the partial discharge of transformer based on ultrasonic method, which can significantly improve the sensitivity of signal detection and the accuracy of location. The research includes the following aspects of contents:1.Design a new form of high-sensitivity ultrasonic sensor. This transducer has a quite wide bandwidth. it not only can detect the low frequency vibration signals, but also can detect the acoustic emission signal. Additionally, it is far more sensitive than traditional acoustic sensor.2.Design a suite of signal processing circuit. It preprocesses the output signal of the ultrasonic transducer. The amplification factor of the circuit is adjustable, with 50 KHz to 150 KHz of frequency range. When it magnifies 100 times, the bandwidth is 100 KHz.3.Utilize a 200 MHz dual-core DSP(digital signal processor) to process signal. The processing unit features four independent 16-bit high speed analog-to-digital converters(ADC), with up to 1MHz of sampling rate each, which can acquire an undistorted ultrasonic signal.4. Write the DSP code and PC(personal computer) application. The DSP communicates with the upper computer through Ethernet. It captures, converts, and stores the acquisition signals in terms of the commands from the computer, and then sends these data results to it. The upper computer restores and displays the signals acquired, meanwhile, it will compute the location of the partial discharge. The precision of calculation reaches 1 centimeter in laboratory.