Effect of the overcurrent protection settings on distributions systems on the resultant power quality

Abstract

At present time, in Argentina as well as in many other countries, the electric companies (utilities) shall follows strict regulations regarding Power Quality, specifically with respect to quality of the technical service (continuity), being penalized thought economic sanctions in the event of regulations non-fulfillment. Such penalties, for our case, are related with the number and duration of the interruptions, for what the companies determine their protective device settings in order to minimize the amounts of those mentioned penalties. One of the usually taken measures is the delay in the operation of the protective device (relay) in order to allow the full operation of the down stream devices with reclosing capabilities (reclosers), reducing in that way the area that would come out without of electric service in the event of a definitive opening. Such a measure is counteractive for those users that possess sensitive equipment (SE), equipment highly prone to be affected by voltage sags or short interruptions. In presence of circuit faults, the delay in intervention of the protection makes that the fault currents remain more time circulating, generating voltage sags of longer duration, increasing the possibility of affecting the SE. On the other hand, voltage sags that at the present time represent around 75% of the customers’ complaint calls, is not yet included in the current Argentinean Power Quality regulations. Cases are described where such a situation gave reason to considerable disputes between customers and electric utilities, until an acceptable solution was reached for both sectors, being described the adopted corrective measures.