Pg 120-124 Electrical Grid Distribution Systems

Flashcards covering key concepts from Electrical Grid I - Distribution, including line characteristics, system functions, circuit design, main vs. tap lines, and WYE/DELTA configurations.

How does the maximum typical length of distribution lines compare to transmission lines?

Distribution lines are typically not longer than $50\,\text{miles}$, whereas transmission lines may be several hundred miles long.

What are the physical characteristics of distribution lines and their structures?

Distribution lines are recognized by shorter poles located closer together (an average of $300\,\text{feet}$ apart), have more equipment mounted on the poles, and typically use aluminum conductors.

What is the primary function of an electric distribution system?

To receive electric power from the transmission system and distribute it to customers at usable voltage levels safely, with acceptable quality and reliability, while allowing accurate consumption measurement for billing.

What objective is a key consideration in the engineering design of a distribution line and has a major bearing on the chosen voltage level?

Delivering electric power with a minimum loss of power.

For what specific application is direct current (DC) distributed instead of alternating current (AC)?

Direct current is distributed in larger cities for special applications such as elevators in high-rise buildings.

How is a substation distribution system analogous to a house's electrical system?

Similar to a house where a main panel uses individual breaker circuits to deliver power to various rooms, a substation has individual circuits leaving the station to deliver power across a service area.

What is an energized wire called, and what are main line distribution circuits composed of?

An energized wire is referred to as a phase. A main line distribution circuit is composed of either three phases and a neutral, or just three phases.

What are main lines also called, and how do they differ from tap lines?

Main lines are also called feeder mains. They are always three-phase, radiate from the station to supply tap lines and customers, and have larger conductors than tap lines.

What defines a WYE or star distribution system?

A four-wire, three-phase circuit with a neutral conductor.

What is "V" phase construction in a WYE distribution system?

It is a configuration where two phases and the neutral are tapped off the main line to serve light three-phase loads.

How are single-phase transformers connected on three-wire distribution circuits that lack a neutral conductor?

On three-wire circuits from a WYE or DELTA source with no neutral conductor, single-phase transformers require two phases and are connected phase to phase.