Comparison of voltage sag and outage cost in urban meshed 110-kV subtransmission network planning

This paper provides comparison of the outage and the voltage sag costs in the 110-kV subtransmission network in the municipality of Helsinki. The main focus is to identify the influence of both voltage sag and failure rates to meshed grids, regarding the estimated economic burden. The network in focus consists of overhead lines (OHL), underground cables (UGC) and combined heat and power (CHP) facilities, whose generation substantially varies according seasonal and weather conditions. The simulation embodies a reliability analysis, using layer and block investigation, and the calculation of four types of faults to frame a voltage sag distribution function. The results show that voltage sag and outage costs present similar magnitude, and due to its significant economic loss, the voltage sag cost should be accounted to the cost function of subtransmission network planning. This simulation accredits constant both the annual load growth and the interest rate for a 40-year project lifetime.