Subtransmission power system amelioration through increased power transfer

Abstract

This dissertation aimed to present considerations and solutions for the amelioration of subtransmission power systems through increased power transfer by reviewing various infrastructure technologies and solution approaches. In South Africa, as a developing country, there are subtransmission grid areas where reliability and spare capacity have respectively declined and become constrained due to various aspects, such as ageing of equipment, lack of maintenance, insufficient funding, insufficient network planning, and increased electrical load growth. This study followed a qualitative descriptive approach based on a case study research design. As fundamental topics, a sample of case studies focuses on constrained overhead power lines, underground cables, and substations in a subtransmission grid setting. The results were obtained by applying the fundamental equipment characteristics through different approaches. Dissimilar approaches to increase power transfer capacity to a specific zone created multiple comparative solutions. Amelioration solutions were presented for various constraints, but no “one size fits all” solution exists. However, it was found that the first step to increased power transfer on a subtransmission line should follow a theoretical re-rating approach. After that, uprating can be achieved through innovative solutions such as the use of new hardware, component upgrades, structure strengthening and restringing. The last resorts are complete upgrades or rebuilds and establishing new infeed sources. This study was limited by not having real-time thermal rating data for analysis. It is recommended that future studies focus on the development of an operations-based statistical rating as an alternative to real-time thermal ratings.