Glossary -Cont. - ufc_3_520

Interior Electrical Systems
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UFC 3 -520-01

June 10, 2002

Asymmetrical Current--A current wave that is not symmetrical about the zero axis.

The current is offset from the zero axis with the magnitude of current above and below

the zero axis unequal.

Automatic Transfer Switch (ATS)--A switch designed to sense the loss of one power

source and automatically transfer the load to another source of power.

Auto -Transformer--A transformer having a single continuous winding, portions of

which are common for the input and output windings.

Available Short-Circuit Current-- The maximum current that the power system can

deliver through a given circuit point to any negligible impedance short circuit applied at

the given point, or at any other point that will cause the highest current to flow through

the given point.

Backup Protection--A form of protection that operates independently of specified

components in the primary protective system. It may duplicate the primary protection or

may be intended to operate only if the primary protection fails or is temporarily out of

service.

Bolted Fault-- The highest magnitude short circuit current for a particular fault location.

The impedance at the fault location i s usually very low or zero for a bolted fault.

Bonding--A reliable connection to assure electrical conductivity. In terms of

grounding, the permanent joining of metallic parts to form an electrically conductive path

to assure electrical continuity with the capacity to conduct safely any current likely to be

imposed.

Bonding Conductor--A conductor used specifically for the purpose of bonding.

Branch Circuit-- The circuit conductors and components between the final overcurrent

device protecting the circuit and the equipment.

Bypass Transformer-- In terms of UPS systems, a transformer that provides ac power

to the UPS loads when the UPS equipment fails, is temporarily overloaded, or is out of

service for maintenance.

Circuit Breakers Incorporating Ground Fault Protection--Circuit breakers that

perform all normal circuit breaker functions and also trip when a current to ground

exceeds some predetermined value.

Clearing Time-- The total elapsed time between the beginning of an overcurrent and

the final interruption of the circuit at rated voltage. For a fuse, the clearing time is

considered the sum of the melting time and the arcing time. For a breaker, the clearing

time is the elapsed time between the actuation of a release device and the instant of arc

extinction on all poles of the primary arcing contacts.

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