Research On Transmission Line Power Frequency Parameters

The transmission line power frequency parameters are the foundation of the load flow calculations, setting calculation of relay protection etc. and also have important significance for the power system working steady, safety and reliably. It mainly includes the positive parameters and the zero-sequence parts. For the multiple-circuits in the same tower or the transmission lines with long parallel segments, it also includes the mutual inductance and the coupling capacitance. And it gives a huge challenge for the parameters measurement due to the mutual inductance effects between different lines. The off-line measurement method can not be fit to the multi-circuit transmission lines which are done at the power-cutting conditions. No doubt on-line measurement method would be the trend for the transmission line parameters measurement.In this thesis, we use an on-line measurement method to study the parameters measurement for the double-circuit transmission lines which is based on the Transmission Line Equation. Firstly, we study the theoretical basis of each parameters measurement method and then introduce the theories and implementations for the on-line and off-line measurement methods. At the same time analyze their merits and demerits.Secondly, we build the model about the positive sequence and the zero-sequence parameters for the double-circuit lines in a same tower, and deduce the transmission line power frequency parameters'calculation formulas based on the Transmission Line Equation. In addition use the simulation tools to verify the accuracy of the formulas. The simulation method is that, at first we can give the system conditions and set up the transmission line parameters'initial value, and get the voltage & current signals after the model running, then calculate the voltage and current phasors, next get the results of the transmission line parameters with substituting the phasors into the calculation formulas, through the contrast between initial value and the calculated, we can confirm the correctness and validity of the proposed calculation formulas.Lastly, we present the scheme of hardware design and introduce the function of each part of the hardware.