Probabilistic Economic Estimation Of Distribution Network Customers With Respect To Voltage Sags And Interruptions

Modern industrial processes consist of equipments highly sensitive to voltage sags and voltage interruptions.Thus,voltage sags result in more load interruptions and enormous economic losses,which is a upset problem to both utility and industrial customers.Evaluating the economic influence on distribution network customers caused by voltage sags has great theory and engineering significance.Voltage sags on distribution network busbars are caused mainly by short circuit faults.However,The relay protection devices remove the fault and isolated distribution network busbars suffer from short duration interruption(SDI)and unplanned long duration interruption(LDI).Voltage sags,SDIs and LDIs all cause load interruptions and affcet customers' successive power supply.The probability of load interruption differs recording to voltage magnitude and duration time of events.Thus,the annual time of voltage sags,SDIs and LDIs and the load interruptions caused by voltage sags,SDIs and LDIs are estimated seperately in this paper.Furthermore,the economic losses are evaluated,which helps to choose economic and effective mitigation measures.This paper proposes a probablistic methodology that includes the actions of relay protection.Then,the annual time of voltage sags,LDIs and SDIs to distribution network busbars are calculated,which makes utility know the influence caused by short circuit faults to the distribution network.Furthermore,voltage-tolerance ranges for different types of equipment are taken into account to quantify annual equipment trips due to voltage sags and voltage interruptions for customers in the distribution network.Then,the economic losses of customers in the distribution network are evaluated recoding to annual equipment trip times.The proposed methodology estimates economic losses due to voltage sags,LDIs and SDIs separately.The results permit the utility to identify a geographic area where customers face high equipment trip probability and enormous economic losses.This can be used to prioritize mitigation measures to those customers most affected by equipment trip.The economic of tipical mitigation measures to distribution network customers is evaluated by net present value method.A probablity distribition model for DG's timing and randomness characteristics is set up,which is used in economic evaluation of DG's mitigation effect to distribution network customers.At the meantime,the impact of DG's rated capacity on economic is analyzed.