Influence of Measurement Uncertainty on Parameter Estimation and Fault Location for Transmission Lines

摘要

Fault location algorithms for transmission lines use the parameters of the transmission line to locate faults after the faults have occurred along the line. Although these parameters can be estimated by the phasor measurement units (PMUs) at the terminal(s) of the transmission line continuously, the uncertainty in the measurements will give rise to stochastic errors in the measured values. Thus, the uncertainty in measurements definitely influences the estimations of the parameters of the transmission line, which, in turn, influences the results of fault location algorithms. Inaccurate results of fault location algorithms may lead to costly maintenance fees and prolonged outage time. Therefore, in this article, we estimate the parameters of the transmission line considering the uncertainty in the measurements so that a more accurate fault location can be derived. The uncertainty in the measurements will be modeled as a stochastic distribution, and the maximum likelihood estimation (MLE) method will be adopted to reduce the uncertainty in the measurements. In addition, as an illustration, the telegrapher's equations will be used to calculate the parameters of the transmission line, and the two-terminal positive sequence network fault location algorithm will be used to locate the fault. In a simulation, a case study of a real-life transmission line the influence of the uncertainty in the measurements on the transmission line parameter estimations and the effectiveness of the MLE method for estimations are simulated and analyzed. The results show that the influence of the uncertainty in the measurements on the positive sequence network fault location algorithm should not be neglected and that the proposed method is very effective in significantly reducing the influence of the uncertainty in the measurements. Note to Practitioners-The objective of this article is to address the significant effects of inaccuracies in the measurements for fault location determination in transmission lines in power systems. These inaccuracies increase the cost and duration of the search process for the actual fault location, and they, thus, also enlarge the outage duration and reduce the power system reliability. This article aims to analyze and reduce the influence of the uncertainties in the measurements in order to obtain a much more accurate fault location estimate when a fault has occurred along the transmission line. One of the key contributions of this article is the development of a model for the uncertainties in the measurements based on a confidence level and deviation bounds; this model can then be used if the information on the distributions of the uncertainties in the measurements is not available. Another key contribution is a maximum likelihood estimation method to estimate line parameters more accurately and consequently to reduce the influence of the uncertainties in the measurements on the fault location estimate.