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 (b) A transformer section includes one or more transformers with or without automatic
load-tap-changing (voltage regulating) capability.
(c) A secondary section provides for the connection of one or more secondary feeders.
Each feeder is provided with a switching and interrupting device.
1.4.2.2 Substation Bus Arrangements. A bus is a junction of two or more incoming and
outgoing circuits. The most common bus arrangement consists of one source or supply circuit
and one or more feeder circuits. The numerous other arrangements and variations are mainly
intended to improve the service reliability through the bus to all or part of the load during
scheduled maintenance or unexpected power outages. Typical bus arrangements are shown in
Figure 1-3.
The arrangements are normally referred to as:
(a)
Double-bus.
(b)
Two-source sectionalizing bus.
(c)
Three-source sectionalizing bus.
(d)
Star or synchronizing bus.
When two sources are used simultaneously, but must not be operated in parallel, a normally open
bus-tie circuit breaker is interlocked with the source circuit breakers. This permits serving both
bus sections from one of the sources when the other is not available. For normally parallel
sources, a single straight bus may be used. It is preferable, however, to use a normally closed
bus-tie circuit breaker to split the system so that service continuity can be retained on either
section when the other section is out of service.
1.4.2.3 Substation Operation. Substations may be attended by operators or designed for
automatic or remote control of the switching and voltage regulating equipment. Most large new
substations are either automatic or remotely controlled.
(a) In an automatic substation, switching operations are controlled by a separately
installed control system. Major apparatus, such as transformers and converting equipment, may
be placed in or taken out of service automatically. Feeder circuit breakers, after being opened,
can be reclosed by protective relays or by the control system.
(b) Remote control substations are often within a suitable distance from attended
stations. In such cases pilot-wire cables provide the communication link to receive indications of
circuit breaker or switch positions and to transmit control adjustments, as required. Microwave
radio, telephone lines, and carrier current are often used for remote-control links at distances
beyond the economic reach of pilot wire systems.
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