Protecting power systems in the post-restructuring era

Protective devices (relays) are the first line of defense against faults and other disturbances that could do extensive damage to power equipment as well as to power systems. They are the most important self-healing mechanisms of power systems. Modern protective systems have evolved into a highly reliable system over many years. As most of the evolution took place during the era of vertically integrated power companies (i.e., where the generation-transmission-distribution-load in a region were all under direct control of a single company), it is natural that protection philosophies in existence today have an in-built character that is well suited to such utility company structures. This paper is a free-flowing exploration of issues that seem to the authors to be significant in the post-restructuring era of the electricity supply industry. They raise many questions from the point of view of power system protection engineers