Measure The Density Of SF₆ Using Fiber Sensor

SF₆ breaker has the electric longevity, simple structure, having little use for maintenance and other merits. It has more and more applications in the field of high voltage. Testing the gas leak in it is one of the important steps to guarantee the safety and normal function of breakers. If the SF₆ fluidify in the low temperature circumstance or let out, the gas density will decline inevitably, it will be certain to reduce the capabilities of insulation and arc eradication. Measuring the density and humidity of SF₆ in the electrical equipment is of consequence. This article takes up with investigating the method to measure the density of SF₆.Because of the high voltage insulation and strong electromagnetic noise, the technique involved electrical signal cannot be applied to the SF₆ density measure system. The fiber sensor has the carrier of light signal and offers a new idea to measure and research the gas density in the high voltage electric equipment. The measuring platform designed by this article use the new photoelectric detector-Position Sensitive Device PSD as the measuring element, the fiber as the light signal transmission channel. It makes fully use of the strongpoint of fiber sensor such as the high voltage insulation and good performance of anti-electromagnetic noise.This article begins with introducing the conception of refrangibility, and then the relation between refractive index and density of the gas is established. The feasibility of measuring the SF₆ density based on the refractive index-sensible-theory is analyzed referred to the principle. According to the traits of the field, in which SF₆ is used, the measuring project is brought forward to measure the density by measuring the ray deflexion. Taking advantage of PSD's high resolving power to the light point position, the SF₆ gas density measuring system is designed including the light pathway and signal-disposal sections. By experiments, the PSD's temperature and frequency response characters are mastered so as to the output performance when the intensity changed. Using solution substitute for gas to make the experiment measuring the solution's concentration. The experiment's results validate the feasibility of the density measurement project, which is advanced by this article.The innovation points of this article: introducing the conception of refrangibility to the density measuring system, put forward the method based on the refrangibility-fixedness theory to measure the gas density, design the signal disposal circuit and establish the experiment platform, working out the gas density measurement using PSD as the sensor for the first time, in which the light signal is medium so the needs of SF₆ application field to the measuring system is meet, to improve the measuring performance of the system, the DC driving system is upgraded to AC driving one and add the corresponding filter to the signal disposal section. In this way the effect of light in the background is weakened and the response of PSD to the changing concentration is proved as the results shows.