TABLE OF CONTENTS P. Fletcher
The function of a substation in a transmission system is to provide a switching node through which circuits, generating units and step-down transformers can be interconnected. Substations are critical to the safety, reliability and availability of the network and should be carefully planned with both current and future system requirements in mind [1, 2],
The need for a new substation will be identified by system planners who will define the key design parameters. Examples of such system requirements are:
general location
extent of the substation
required availability of circuits
switching arrangement
transformer ratings and impedances
normal current rating
fault current levels
neutral point earthing
fault clearance time with respect to system stability
need for future extensions
control facilities
equipment characteristics.
Where applicable, it is generally advisable to select system requirements to align with IEC or EN Standards. Many utilities also find it beneficial to specify technical requirements so as to allow the use of standardised HV equipment with identical characteristics (e.g. short-time current level, maximum current carrying capacity, characteristics of transformers, insulation level).
Some of the more common switching arrangements used in UK practice [1] are as follows.
This arrangement has been widely used in the UK at both transmission and distribution voltages for larger substations where security of supply is critical (see Figure 9.1). Each circuit is provided with a dedicated circuit-breaker (1) and can be selected to either of the two independent busbars...
