Английский в энергетике

DESIGN AND LAYOUT

      The main issues facing a power engineer are reliability and cost. A good design attempts to strike a balance between these two, to achieve sufficient reliability without excessive cost. The design should also allow easy expansion of the station, if required.[edit]

      In the largest stations, incoming lines will almost always have a disconnect switch and a circuit breaker. In some cases, the lines will not have both; with either a switch or a circuit breaker being all that is considered necessary. These devices are used as isolation and protection devices. A disconnect switch is almost always used solely to provide isolation, due to it not being rated for breaking a loaded circuit, while a circuit breaker is often used both as an isolation element as well as a protection device.^[clarify] Where a large fault current flows through the circuit break this may be detected through the use of current transformers. The magnitude of the current transformer outputs may be used to 'trip' the circuit breaker resulting in a disconnection of the load supplied by the circuit break from the feeding point. This seeks to isolate the fault point from the rest of the system, and allow the system to continue operating with minimal impact.

      Once past the switching components, the lines of a given voltage all tie in to a common bus. This is a number of thick metal bus bars, in most cases there are three bars, since three-phase electrical power distribution is largely universal around the world.

      Substations that require additional reliability often have a double bus or even a double ring bus, in which the bus system is actually duplicated, with each feeder  having a connection to each separate bus. Most substations will not have this, as it is mainly for reliability in substations whose failure would bring down a substantial part of the system, or whose load is of vital importance. Other compromises between a single and double bus can be found; for example, the breaker-and-a-half setup.

      Once having established buses for the various voltage levels, transformers may be connected between the voltage levels. These will again have a circuit breaker, much like transmission lines, in case a transformer has a fault (commonly called a 'short circuit').

      Along with this, a substation always has control circuitry needed to command the various breakers to open in case of the failure of some component.