Study On The Integrative Measuring System Of Insulating Oil Dielectric Loss And Volume Resistivity

The measurement of dielectric loss and volume resistivity is effective preventive tests to judge insulating oil isolation status of polluted and aging, and it's important method of ensuring the safe operation of transformer and oil-filled circuit breaker, etc. However, the measuring systems of insulating oil dielectric loss and volume resistivity used at present exist the shortcoming of low accuracy, weak repeatability, inconvenience, and its thermostatic control system can't meet the challenge. So, this paper researches the principle of measuring system of insulating oil dielectric loss and volume resistivity.During the measuring process, the insulating oil must be heated and kept at 90℃ in 15 minutes. Medium-frequency induction heating method is presented to instead of the electrical resistance furnace heating method on chapter 2, and a kind of subdivision-controlled integral-separated digital PID algorithm is designed to control the medium-frequency induction heating apparatus. The experience results indicated the reliability of this kind of thermostatic control system.The analysis and compare about modern dielectric loss measuring methods are presented on chapter 3, and the zero-crossing testing phase discrimination method is adapted as the measuring method of this measuring system. Furthermore, applied high frequency pulse technique, channel self-correction technique, anti-harmonic technique are used to increase accuracy and reliability of measurement. And a kind of 16-step automatic selective programmable amplifying circuit is designed in volume resistivity measuring circuit, so as to handle sampling little and broad signal.The control and disposal system with the core of microchip AT89C55WD is analyzed on chapter 4. Main function unit such as the interface circuit of LCD display and keyboard, the interface circuit of micro-printer, real time clock DS12C887, and hardware anti-jamming technique are discussed. Actual measurement result for different oil sample is analyzed and compared on chapter 5.