TABLE OF CONTENTS Substations are the points in the power network where transmission lines and distribution feeders are connected together through circuit breakers or switches via busbars and transformers. This allows for the control of power flows in the network and general switching operations for maintenance purposes. This chapter describes the principal substation layouts, the effects of advancements in substation equipment, modular design, compact substations and the moves towards design and construction turnkey contract work. The descriptions concentrate on air insulated switchgear (AIS) outdoor open terminal designs at rated voltages of 72 kV and higher. The design of distribution voltage switchgear and gas insulated switchgear (GIS) is described in Chapter 13, in which terminology is also defined.
In an ideal situation all circuits and substation equipment would be duplicated such that following a fault or during maintenance a connection remains available. This would involve very high cost. Methods have therefore been adopted to achieve a compromise between complete security of supply and capital investment. A measure of circuit duplication is adopted whilst recognizing that duplication may itself reduce the security of supply by, for example, providing additional leakage paths to earth.
Security of supply may therefore be considered in terms of the effect of this loss of plant arising from fault conditions or from outages due to maintenance. The British Code of Practice for the Design of High Voltage Open Terminal Substations BS 7354 categorizes substation service continuity; recognizing that line...
