Consideration of voltage sags disruption risks in distribution planning studies

The new industrial processes based on electronics and the need for compatible power quality at customer connection points must change the traditional distribution planning models. Instead of considering only costs of equipment used to reinforce or expand the distribution network as well as the costs of losses obtained from a power flow calculation, this article presents a methodology for distribution planning analysis considering power quality indices. Modernization of distribution companies requires reducing the number of energy interruptions. Due to the sensitivity of new industrial processes, voltage sags can be, regarding the customer, so severe as an interruption can be. A disruption (equipment failure) of the process can stop it or originate production losses, which may consume hours to re-start it again. To monitor the power quality considering a number of disruptions, this article presents the expected index of disruption, resulted from Monte Carlo simulation. Considering these indices, calculated for the whole electrical network, it is possible to compute the average index expected for each one of the feeders and substations. This average index indicates the expected number of disruptions taking into account the customer side sensitivity curves. Therefore, the objectives to be considered in the planning study include the minimisation of the number of occurrences of voltage sags, specifically those that can affect the industrial processes connected in network. A comparative table can be further analysed showing the average number of disruptions found for all busses in each feeder and substation. Thus, the developed study allows the distribution planner to estimate the cost of each one of the prevented disruptions, allowing a choice of reinforcements based on the best option of planning.