Research On Air Insulated High Voltage Transformer Based On Modular Interference Of Optical Fibre

Optical voltage transformer (OVT), as a novel kind of voltage transformer, is ableto meet the requirements of the smart power grids and will become the essential partof the smart power grids. However, low accuracy, low stability and low reliability arethree obstacles that must be tackled to make OVT practical: With the fast developmentof smart power grids, the research on the practicality of OVT is more and morepromising.In this dissertation, the development and present situation on OVT research isillustrated. According to the problems faced by OVT, all fiber voltage transformerbased on modular interference in polarization maintenance fiber is studied. Severalproblems, including the design and optimization of high-voltage element, the analysison the performance of the sensors under different conditions and interference lobespick-up and detecting, are studied in details to accelerate all fiber voltagetransformer’s practicability process. The main contents of this study are as follow:First, an all fiber voltage transformer is designed and its principle is illustrated.This transformer works based on modular interference in polarization maintenancefiber and piezoelectric effect in quartz crystal. By employing finite element method,the modular interference properties of elliptical core polarization maintenance fiberand polarization maintenance photonic crystal fiber are numerically calculated. Thecutoff property of second order mode is studied and the relationship between modularinterference beat length and wavelength is also researched for both fibers. The sensingprinciple of the system is analyzed. The theoretical model also is established.Second, the electric field distribution in high-voltage part of the all fiber voltagetransformer is numerical simulated by finite element method. The influences of theinsulator’s internal diameter, the thickness of epoxy resin, the distance between quartzcrystals and the distance between supporting pillar and the interior walls of insulatoron the electric field distribution are studied thoroughly. Based on the research above,the structure of the sensor is optimized. Third, the performances of the sensor in all fiber voltage transformer are studiedunder different conditions. The influence of temperature change on the volumeexpanding and piezoelectric effect of quartz crystals is researched. The thermo-opticand thermal expansion effect of elliptical core polarization maintenance fiber is alsostudied when temperature changes. Base on these researches, the theoretical model oftemperature’s impact on high-voltage element in all fiber voltage transformer isestablished. The temperature self-adaptive feedback and compensation system is alsoproposed to reduce the impact of temperature perturbation.Fourth, the relationship between modal field radius of elliptical core polarizationmaintenance fiber and wavelength is analyzed. Based on the analysis and comparisonwith several methods, an interference lobes pick-up and detecting scheme is designedand optimized. Its reliability is validated through experiments.At last, the modular interference beat length in polarization maintenance fiber ismeasured by modulating fiber length through piezoelectric ceramic. The temperatureself-adaptive feedback and compensation scheme is also validated. The reliability ofthe all fiber voltage transformer is tested by high-voltage experiments, theexperimental results are analyzed.