The Influence Of The Accuracy Of Real-time Measured Data On Transmission Cost Accounting

Transmission cost represents the cost of transporting electricity power during the transmission link for grid operation companies. For increasing the efficiency of manufacture, operation and adapting to the market economy, transmission companies should grasp the transmission cost accurately. The alterable transmission cost such as network loss would change with the operation conditions of electric power system. When considering only the influence of network loss on transmission cost, it involves physical and economy levels. It must meet conservation of energy and basic circuit theory and provide the source of each power in the network on the physical level. It also must meet the principle of break even on the economy level. The power distribution theory based on electric network and the conversation of transmission cost principle can be used to fairly and correctly carry out transmission cost accounting respectively at physical and economy levels. Power tracing at the physical level is the theoretical basis of transmission cost accounting. The accurate online power calculation is the premise of accurately acquiring power tracing results. Therefore the first issue of researching transmission cost accounting is analyzing the accuracy of online power flow calculation.Online power flow calculation acquires the actual operation conditions of electric power system whose given data are provided by SCADA system. The accuracy of online power flow calculation is determined by the power flow computational algorithm and real-time data. At present, the computational algorithm has been fully developed. Therefore real-time data become the key fact of influencing the accuracy of online power flow calculation. Only when real-time data were accurately measured can the online power flow calculation results c accurately reflect the actual operation conditions. It is pointed out there exists errors in the real-time data through the analysis of measurement process of real-time data. Among these errors, the measuring error of reactive power is the biggest, the measuring error the active power comes second and the measuring error of voltage is the smallest. Base on this, this paper proposes an online power flow calculation with improved given variable option. Voltage magnitude and active power whose measuring accuracy is comparatively higher are selected to be given variable. The load buses are set to PV buses and both the injection powers and bus voltage vectors are acquired thought real-time measurement in the improved method. IEEE9node example is selected to simulate the improved method on MATLAB platform. The simulation results indicate that the convergence of the improved and classic methods is the same. The power flow result calculated by the improved method is closer to the perfect power flow, and the transmission cost calculated by the improved method is more accurate than that calculated by the classic power flow calculation method.