Sensitivity and Viability Analyses of Overhead and Underground Meshed Subtransmission Networks

Abstract

This paper investigates the economic impact of installing underground cables and overhead lines directly connected to a selected test substation on the delivery point. For this, a two-part assessment performs firstly a sensitivity analysis to measure the reliability performance in a typical urban meshed subtransmission network based on collected data from the local utility. The technique employed is a blocked-structured tool that can determine the influence of each of the four main groups of equipment given the parameters at each scenario, determined by customer types and weather conditions. Secondly, the viability analysis compares the reliability indices, the outage and the voltage sag costs of seven different cases, using either underground cables or overhead lines in a number of connections. The target is to identify the most inexpensive solution in terms of total cost within the acceptable limits of unavailability. The results of the sensitivity analysis indicate that the substation arrangement and its equipment generate the largest influence on the system availability and outage costs, particularly in substations with local generation. In addition, substations without local generation are more susceptible to the type and number of connections. The viability analysis indicates that the combination of maintenance, losses, outage and voltage sag costs in opposition to investments launches underground cables as a competitive alternative to overhead lines in high-voltage systems.
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