Electric Energy Measurement Method for Traction Loads

In order to explore the influence of negative sequence from traction loads on electric energy measurement results, the negative-sequence power flow in traction power supply system is analyzed on the basis of the established traction power supply system and three-phase power system models. The shortcomings of the power factor metering method based on the traditional power theory are provided. In this regard, an unbalanced power factor metering scheme for traction load is proposed according to the equivalent apparent power and power factor definitions recommended by the IEEE Std 1459-2010 power theory, in which the limit of the effective power factor is 0.68. Theory analysis and measured data show that the direction of negative-sequence active power is opposite to that of the positive-sequence active power; as a negative-sequence source, traction loads add negative-sequence power to the system, which can eventually be absorbed by the system impedance and balanced load. Finally, algorithm effectiveness and conclusion correctness are analyzed and validated by simulation and statistical analysis on 56 groups of measured data in this paper. The simulation and statistical analysis on 56 groups of measured data are used to validate the algorithm and conclusions. Statistical results of measured data show that the equivalent apparent power and the definition of power factor can account for the effect of nonlinear unbalanced traction load on transmission efficiency, which is more reasonable and accurate.