Research Of Metering Standard Device In Industry Of Heavy Direct Current

Heavy direct current has a wide range of application in electrolysis industry. With the rapid development of UHVDC, heavy direct current will be much more widely applied in power systems. However, at present, it is more and more eager to develop a unified metering standard of heavy direct current and related metering standard devices to avoid prodigality of energy and underline the active relationship between metering and economizing on energy. This thesis is supported by Special Projects as Scientific Research for General Administration of Quality Supervision, Inspection and Quarantine of China(No.200710107). A metering standard device used in industry is deeply studied to support its accuracy and reliability, not only can which measure heavy direct current online, but also calibrate direct current transformer conveniently.This thesis introduces the actuality in this field and indicates the significance of this research firstly. A difference double-cores magnetic modulator suited for detecting weak direct single and a direct current comparator based on such magnetic modulator is shown in Chapter 2. A magnetically modulated DC comparator with multi-channel and openable-core type is finally adopted in view of different kinds of problems in industry. In Chapter 3, hardware composed of sensor, processing circuits and digital display is shown. And processing circuits are made up of filter, phase sensitive modulator, direct current amplifier, power amplifier.The emphasis of this thesis is analyzing the ratio-error and testing method in Chapter 4. Current transfer coefficient is introduced to rigidly prove the ratio-error of metering standard device is its relative error virtually. The equations are deduced based on voltage difference method and current difference method respectively, and experimental results account for the ratio-error is less than 2×10-4 according to the simulation of industrial circumstance in Heavy Direct Lab of HUST.In Chapter 5, characteristics of antimagnetic and air clearance and the reasons of working in balance are discussed in theory, and summing-ups and prospects of this research are proposed in the end.