Letter S

Safety Switch

A type of enclosed switch that may also include provisions
for fuses. Single-throw safety switches are used to provide a
means for disconnecting power. Double-throw switches are
used to transfer loads from one power source to another or to
transfer power from one load to another.


Secondary Unit Substation

A coordinated design consisting of one or more transformers
mechanically and electrically linked to switchgear or
switchboard assemblies with an outgoing voltage rated below
1000 volts.

Selective Coordination

Applying circuit breakers in a manner that minimizes the extent
of an outage in the event of a fault. Circuit breakers are typically
installed in a branching arrangement. In the event of a fault, the
breaker electrically closest to the fault should trip first. This can
be accomplished by properly sizing and adjusting all breakers.


Selector Switch
A manual switch with multiple contact positions.

Semiconductor
A type of material, such as silicon, with more resistance than a
conductor, but less than that of an insulator. Semiconductors
can be manufactured to produce devices such as diodes,
transistors, thyristors, etc.