Stochastic Assessment Of Voltage Sag And The Research On The Indice

Voltage sag has been become one of the major problems of power quality recently.The sag events caused by short-circuits on lines would have different effect toward kinds of buses.In this paper,the stochastic assessment of voltage sags and construction of voltage sag assessment system are discussed.Firstly, the methods of stochastic assessment are analyzed and compared,then a Monte Carlo simulation combined with symmetrical component method is put forward to be applied in the stochastic assessment of voltage sags caused by short circuit.fault. Given the shortcomings of other methods, a method using SARFI index's confidence interval and its frequency is strongly suggested to evaluate the influence brought by voltage sag on the basis of stochastic assessment's results, what's more, in order to obtain the accuracy of SARFI index's value, a method of nonparametric estimation. is introduced. Secondly, On the basis of a general five-step framework proposed by IEEE project group P1564 for obtaining system indices for voltage sag performance, parts of indices studied by some international organizations like IEEE and IEC, etc. are analyzed and organized in this paper, while some indices are recommended to be adopted from aspects of single event, single site and system respectively by summarizing their merits and shortcomings, then a set of specific and complete assessment system is proposed, including a variety of indices and feature extraction methods.