The Design Of Portable Partial Discharge Detector

With the development of urban electrical network, an increasing number of GIS and transformer equipments are applied. Due to the high operating voltage and the limited space, the operating field density of GIS and transformer equipments are high, thus equipment failure can easily occur once some certain defects are existed in the GIS and transformer equipments.Strengthening and improving the commissioning test and operation monitoring of GIS and transformer equipments, especially the detection of the frequent incidence of partial discharge (PD) fault and the development of new types of testing equipment,are of great significance to the safe operation of equipments.Based on the drawbacks, such as low sensitivity and inconveniency to carry, of conventional instrumentations for PD detection, on the basis of summing up the current study of PD on-line monitoring, this thesis introduces the circuit structures and properties of portable PD detectors,explores and applies a partial discharge detection circuit based on the phase-locked amplification technique.Weak signal can be extracted from the noise in the circuit, thus increasing the detection sensitivity. Finally, test results and results analysis are given.The main contents of this thesis are listed as follows:(1) The causes of PD in GIS and some commonly used methods of PD measurement are analyzed.In the measurement, phase-locked amplification technique are used to improve the sensitivity and anti-interference ability of partial discharge detection circuit.(2) Based on the working principle of phase lock amplifying circuit, implementation of the portable PD detector is given. The structures and functions of each unit are analyzed.(3) Based on the design requirements for portable PD detectors, the detailed designs of antenna probe module,microwave detector module,square-wave reference signal module,lock-in amplifier module are given. Relevant circuits are simulated.(4) Debugging and testing work are applied to the lock-in amplifier module. It can be concluded from the test results that the weak signal can be extracted from the noise.