Study On Transfer Characteristics Of Electronic Current Transducer And Adaptive Protection Principle

Current and voltage transducers as the power measurement equipment, are responsible for monitoring a primary device and providing true and reliable electric quantities to the secondary equipment. Electronic current transducer (ECT) as the representative of the new electronic transducer circuit has no electrical contact with the measured current circuit, has the frequency bandwidth, low output, simple structure, good linearity and other significant advantages, which solves the traditional electromagnetic transient current transducer saturation and low accuracy problem. With the continuous development of power system, it is an irreversible trend that a new generation electronic transducer replaces the traditional transducer.The output of the electronic transducer is a digital signal, which is essentially different with the analog signal output of the traditional transducers. This will have a profound impact on the secondary equipment and its test system. This paper takes properties of electronic transducer as a main research and analyzes the important content of the following aspects:this paper proposed the digital modeling idea of electronic transducer and studied the sensor system composition of the electronic current transducer and frequency domain characteristics, and constructed several typical ECT modeling program, and complete the model simulation and experimental verification. The thesis researched on the interface technology based on electronic transducer, explore measuring and protective equipment to make a new applications of current and voltage signals from the electronic transducer, promoted research on the new protection principles, proposed a idea that directly use electronic transducer differential signal as a protection input, put forward the new RL models principles and the new differential protection principle based on the differential input signal, and made the theoretical analysis and simulation studies, and acquired a number of important research results. In allusion to the blankness which test means of protection is adapted to electronic transducer, the paper proposed a new thought of real-time simulation test system based on IEC61850, and built the new dynamic simulation systems and real-time digital simulation of RTDS system compatibile with electronic transducer. In a new real-time simulation environment, the paper made a comparative characterizer experiments between the electronic transducer and the traditional transducer, analyzed the importation made by the electronic transducer to the traditional protection principle. The main work of this paper is following:1, Digital simulation modeling is completed of electronic current transducer based on Rogowski coil, the paper made a detailed study on simulation model of the entire sensor system in Rogowski coil measuring circuit. Using PS CAD to make a simulation test and through analysis of the process of steady state and transient fault simulation, this paper demonstrated that the digital model followed the primary signals well; Using PSCAD simulation system as a data source of digital transducer model, its output data and the actual dynamic model data of transducer was exported into MATLAB to make a comparative analysis. The experimental results prove the correctness of the modeling approach.2, To upgrade the traditional dynamic simulation experimental system and to build a new type of physical simulation system compatible with digital dynamic simulation and traditional dynamic simulation. In the new physical simulation environment, taking the protection as a application object, a performance comparing test was made between the conventional electromagnetic transducer and the of electronic transducer. It is analyzed that the application of electronic transducer effects on traditional protection principle. It is focused on the operating characteristic curve of line differential protection in the different fault conditions after using electronic transducer. The research results show that the safety and the reliability of line differential protection is observably improved because the electronic transducer has no saturation in case of high current.3, Two interface modes of the electronic transducer and relay protection system is discussed, namely:Firstly, in order to reflect the voltage and current, the outside integral circuit is increased in the sensor system of electronic transducer to achieve connection; Secondly, omits the transducer integral part and modify the traditional protection algorithm, the differential signals from electronic transducer are used in protection algorithm directly.4, This paper analyzes the characteristics of two different interfaces and proposes the R-L protection principle and the differential protection principle based on the differential input signals. The theory is correct and feasible through theoretical analysis and simulation. The electronic current transducer differential signals are applied to protection algorithm directly. It can give full play to the advantages of electronic transducer and improves the reliability and accuracy of protection.5, A new digital simulation test method is proposed based on electronic transducer and a new simulation test system is constructed. After using electronic transducer, the real-time digital simulation system no longer need to D/A conversion and power amplification and so on, generated directly to the simulation data can be used after format conversion. This paper discusses the new digital simulation system structure and implementation based on the IEC61850 standard, describes the test model connecting RTDS and full digital secondary equipment, and verifies the practicality of the new test system through 110kV line digital protection experiment.Finally this paper summarizes the research results above and proposed the further research direction.