Underground Residential Distribution Systems Definitions

Boot

A piece of insulating material used to cover secondary terminals of a dead-front transformer.

Bushing

A device that allows a conductor to penetrate an equipment enclosure, yet remains electronically isolated from the enclosure.

Cable Fault

A failure and electronic cable that interrupts normal current flow.

Cable Plow

A machine mounted at the rear of a tractor that can dig a trench, lay cable, and backfill the trench in one operation.

Cable Pole

The location of the connection between a URD system and an overhead system.

Cable Tag

A tag attached to a primary cable on a transformer or switch that has phase and destination information on it.

Dead-Front Transformer

A type of pad-mounted Transformer that has a primary, and sometimes secondary terminals that are covered with insulating material.

Direct-Buried Transformer

A transfer that is installed in a below-ground fault that is capped in concrete, and not easily accessible. ___ Transformers may also be buried directly in the Earth.

Disconnect Switch

A device that can be opened or closed to allow all parts of what you are the system to be the de-energized or energized.

Double Feed Design

A URD system design that enables a customer to be connected to URD systems, each energize from a different source.

Fault Indicator

A device that indicates whether a cable has faulted. ___ are often found on load-break elbows.

Fuse

The device that protects URD equipment from damage caused by overcurrent.

Fused Disconnect Switch

A disconnects switch equipped with a fuse. If a fault occurs with the system, the fuse blows, opens the switch and protecting the system.

Grounding

The type of protection use on URD systems that provides a low resistance path to ground for current flow if over voltage or fault occurs.

Information Plate

A plate mounted on a piece of equipment that contains detailed information about the piece of equipment.

Live-Front Transformer

A type of pad-mounted Transformer that has exposed energized metal components on both its primary and secondary sides.

Load-Break Elbow

The device that connects primary URD cables to a piece of equipment. ___ are designed to be disconnected while under load.

Loop Feed Design

A URD system design in which both ends of the system are connected to the overhead.

Mole

A type of terminal strip that is enclosed in a moisture-proof cover. ___ could be installed in pedestals or buried directly in the ground.

Parking Bushing

And insulated, unenergized bushing on a Transformer.

Pedestal

A ground-level weather-proof enclosure that provides a central location between customers for devices such as terminal strips.

Pothead

A device used to protect the connection between a URD and an overhead system. A ___ also provides a termination for the URD cable insulation.

Radial Feed Design

A URD System design in which only one end of the system is connected to the overhead.

Secondary Main

A URD cable that connects a pedestal-mounted terminal strip to the secondary side of a transformer.

Subsurface Transformer

A Transformer that is installed below-ground fault that is covered at ground level with a grating.

Surge Arrester

The device used to protect a system from damage caused by lightning strikes or voltage surges.

Tap Hole

A vault-mounted switching point that allows sections of underground cable to be energized or de-energized.

Terminal Strip

A device that allows several different cables to be connected at one point. ___ maybe mounted directly on transport secondary bushings or in pedestals.

Three-Phase Open Loop

An open URD system that consists of three separate open loops that all run in the same trench. Each Loop is energized by a different phase of the overhead.

Transclosure

A pad mounted switch that is used to connect the ends of a URD loop to an underground feeder.

Transformer

In a URD system a device that changes the primary distribution voltage to secondary voltage that customers use.

Underground Feeder Cable

A type of cable that is found in some URD systems that is installed between the substation and URD pad-mounted switches.

URD System

An underground residential distribution system; a local distribution system designed to be buried in the ground