PG 145-149 Distribution Circuit Designs and Easements

Flashcards covering radial, radial tie, and network grid circuit designs, as well as line route easements, franchise agreements, and joint-use requirements.

What are the three basic distribution circuit design arrangements?

1. Radial
2. Radial Tie
3. Network Grid

What is a Radial circuit design and how are its transformers installed?

A design where circuits are independent and radiate into the service area, with transformers installed individually to supply power to customers at the desired voltage.

Why does the Radial circuit design have the least reliability among the three basic designs?

Because if a permanent fault occurs, there is no opportunity to restore power from another source.

How does a Radial Tie circuit design operate to increase reliability?

Circuits can be connected together automatically or manually at one or more points using a tie switch, allowing power to be supplied from other circuits in case of trouble or maintenance.

How are step-down transformers and circuits arranged in a Network Grid design?

The circuits and step-down transformers are connected together in parallel to form a low-voltage network grid.

What are the typical voltage levels for a three-phase low-voltage network grid?

$120/208\text{-volt}$ or $277/480\text{-volt}$ low-voltage network.

What happens if one transformer fails in a Network Grid design?

It is automatically disconnected and does not affect service due to having several sources of power.

Where is the Network Grid design typically utilized, and what are its primary traits?

It is typically found in larger cities with high-rise buildings in metropolitan areas. It is the most reliable design, but also the most expensive.

What is the standard conductor configuration for almost all distribution circuits?

Four-wire: three phase conductors and one neutral conductor.

What are the first considerations when building a distribution line?

The route of the line, associated terrain, and existing development.

What agreement allows a utility to install facilities in utility easements preserved by a city?

A franchise agreement.

What legal requirement must a utility fulfill to install distribution lines on private property?

The utility must secure an easement from the landowner.

What rules apply to telecommunication companies using power company poles or joint-use trenches?

Telecommunication companies have the right to use power poles but must provide compensation for the value; the cost of joint-use trenches may also be shared among participating utilities.

Which standard sets the proper strength and clearance requirements for pole lines and joint-use underground trenches?

The National Electric Safety Code.