Research On Digital Optic-Electric Transducer And Its Application To Relay Protection

With the rapid development of micro-electronic technology, optic-electric technology and communication technology, measurement and control technology, including intelligent, digital and network technology, are applied in electric power system steadily. They are changing the mode of operating, maintenance and management of conventional electric power system profoundly. Especially for the application of Optic-Electric technology and its combination with information technology, it will put conventional electric power system into a technological revolution. Being the electric parameter acquisition device, current transformer and potential transformer were chosen to be research objects of this thesis. The study of measurement principle of novel Optic-Electric Transducer (OET), the study of transmit mode of electric parameter in secondary circuit and the study of theory and problems during the applying OET in measurement, control and relay protection device, are carried out in this thesis.Based on a large number of references from China and abroad, the history, tendency and latest developments of the technology about OET in china and abroad are introduced. The advantage and disadvantage of conventional transformer, passive optical-fiber transducer and active OET are compared. Active OET (AOET) is then chosen as emphasis of current practical research topic. According to the current situation and prospect of applying OET in substation automation, the opinion of digital electro-optical secondary circuit is given out. The main research topics and contents of every chapter are described finally. In the research of measurement principle of AOET, problems of conventional transformer are discussed through transient process simulation at first. The disadvantages of electromagnetic current transformer and capacitive voltage transformer are demonstrated too. The electric characteristics and transient process characteristics of Rogowski coil based current AOET are then analyzed in details. The integration design method and example of AOET are provided. Experimental results of steady error test and dynamic simulation test prove that AOET is applicable in measurement, control and relay protection of electric power system completely.The signal output from transducer in high voltage side should be integrated, analog-digital converted and electric-optic transformed at first, original current and voltage value then can be transmitted down to low voltage side in substation. Optic electric measurement system, which consists of electronic circuit in high voltage side and data acquisition & signal processing in low voltage side, is taken into discussion. The ideal schemes of measurement channel and control channel in high voltage side are proposed by the comparison of different kinds of technical schemes. The improved Voltage-Frequency conversion (VFC) scheme that used in analog-to-digital conversion process has many merits, such as high AD resolution, fast sample rates and without synchronic sampling problems. Its practical usage should be further discussed. On the base of introduction of the IEC 60044-7/8 standard, the system structure, interface specifications and communication protocols of Information Merging Unit (IMU) in low voltage side is put forward. The prototype of IMU is described.Novel digital electro-optical secondary circuit, which defines the link between digital output from IMU and secondary device through optical communication network, is one of important research topics of this thesis. The defects of metal cable analog communication are introduced first, the characteristics of hierarchical & distributed substation system structure are then given. A full analysis and discussion of digital electro-optical secondary circuit are carried out. It begins from IMU network topology description to protocols discussion about data link tier, transmission & control tier. The application of IEC 61850 standard in application tier is also discussed. The construction and realization of digital electro-optical secondary circuit...