Overhead Line Zero Sequence Parameter Live Measurement Method

The transmission lines'zero-sequence parameters are the basis of power system relay protection setting, so their accurate measurements are very important to the safe operating of the transmission line and power system. With the development of the power system and constraints of the corridor, mutual inductance lines are increasing, it becomes more and more difficult to obtain the accurate zero-sequence parameters of transmission lines. In several methods to get transmission lines'parameters, live line measurement needn't any power failure or needn't all power failure to achieve the transmission lines'parameters. This method is the development trend of measuring transmission lines'parameters in the future, so its studies have theoretical value and practical significance.Firstly, three live line methods about measuring mutual inductance lines'zero-sequence parameters including incremental method, differential method, integral method are in deeply analyzed and compared, then select differential method and integral method as the main study object to research their identifiable conditions. A proposition is proposed the following:in order to measure zero-sequence parameters accurately,n mutual inductance lines need the data of at least n different operation modes. This dissertation proves the proposition, then establishes model, makes simulations and compiles program in Matlab environment. Experiment results of simulating on lines with two, three, and four circuits validate the proposition. Verifications, complements and modifications are made for some of the literatures.Secondly, the possibility of using transient measurement data produced by disturbance to identify parameters is explored, which was proposed in the related document. Three examples show that it's impossible to solve zero-sequence parameters just using transient measurement data in one operation mode.Finally, in order to reduce the effect of measurement noise existed in the zero sequence current and zero sequence voltage to identification results, first measurement data are sine curve fitted, then samples the fitted curve discretely. Simulation and experiment results show that this method has a good result and improves the parameters estimation accuracy.