Get premium membership and access questions with answers, video lessons as well as revision papers.
Underground cables are generally required in urban areas where there is a high
density of population. The highest load density and the most restrictive limitations on
feeder layout occur simultaneously in the central cores of major cities. Load densities
are usually in the range of 60 to 100 MW per square mile.
Some problems associated with underground cable systems are as follows:
urban area are densely populated with/pedestrian walk ways, as well as water, sewer,
storm drain, phone and other utility systems in addition to electrical. So there is
limited room. The electrical utility must stake its claim to the routes and space
allocated to it with its own duct banks.
Secondly, duct banks are needed to protect underground cable from the constant dig-
ins of other utilities, stress form settling, and heat and moisture in this environment.
Thirdly, digging into the street in an urban area for new additions or repairs is very
expensive. Traffic control and other requirements add to cost and also digging around
all the other utilities. Thus electric utilities have no choice but to use duct banks and
cable vaults to create their own “cable tunnel system“ under the streets in dense urban
areas.
Finally branching of underground cable providing for “T” or “X” connections of
paths, while possible, is not as simple or as inexpensive as in overhead lines.
Summarizing, the underground urban area systems have the following characteristics
• Layout is restricted to street grid
• Loads are large and invariably three phase
• Fixed cost is very high
• The cost of capacity shortfall is extremely high
gregorymasila answered the question on February 20, 2018 at 16:11
- Explain the working of nickel cadmium cells with its merits and demerits over lead acid cell(Solved)
Explain the working of nickel cadmium cells with its merits and demerits over lead acid cell
Date posted: February 20, 2018. Answers (1)
- What are the advantages of high voltage transmission? Give its limitations also.(Solved)
What are the advantages of high voltage transmission? Give its limitations also.
Date posted: February 20, 2018. Answers (1)
- List the advantages of nuclear power plants over conventional thermal power plants.(Solved)
List the advantages of nuclear power plants over conventional thermal power plants.
Date posted: February 20, 2018. Answers (1)
- What is the fundamental difference between thermal and nuclear power plants?(Solved)
What is the fundamental difference between thermal and nuclear power plants?
Date posted: February 20, 2018. Answers (1)
- What are different welding controls used in resistance welding?(Solved)
What are different welding controls used in resistance welding?
Date posted: February 20, 2018. Answers (1)
- With the aid of sketches explain the operation of a four stroke engine(Solved)
With the aid of sketches explain the operation of a four stroke engine.
Date posted: February 16, 2018. Answers (1)
- Name 3 drawing instruments commonly used in technical drawing and define the use of each tool(Solved)
Name 3 drawing instruments commonly used in technical drawing and define the use of each tool
Date posted: January 26, 2018. Answers (1)
- Highlight different methods of water treatment.(Solved)
Highlight different methods of water treatment.
Date posted: January 15, 2018. Answers (1)
- Name any five factors which determine choice of roof structure(Solved)
Name any five factors which determine choice of roof structure.
Date posted: January 1, 2018. Answers (1)
- Give five functional requirements of foundations(Solved)
Give five functional requirements of foundations.
Date posted: January 1, 2018. Answers (1)
- Explain how to test for silt content in sand.(Solved)
Explain how to test for silt content in sand.
Date posted: January 1, 2018. Answers (1)
- List five causes of unsealing of traps(Solved)
List five causes of unsealing of traps.
Date posted: January 1, 2018. Answers (1)
- State 5 principles of a good drainage system.(Solved)
State 5 principles of a good drainage system.
Date posted: January 1, 2018. Answers (1)
- What is critical Mach number in high speed flight?(Solved)
What is critical Mach number in high speed flight?
Date posted: December 29, 2017. Answers (1)
- Give reasons as to why a star delta starter is preferred with induction motor(Solved)
Give reasons as to why a star delta starter is preferred with induction motor
Date posted: November 6, 2017. Answers (1)
- State four advantages of using aluminum tubes over steel when making scaffolds.(Solved)
State four advantages of using aluminum tubes over steel when making scaffolds.
Date posted: October 11, 2017. Answers (1)
- Explain briefly two reasons why blinding is necessary.(Solved)
Explain briefly two reasons why blinding is necessary.
Date posted: October 11, 2017. Answers (1)
- Give four methods of transporting wet concrete to the required position.(Solved)
Give four methods of transporting wet concrete to the required position.
Date posted: October 11, 2017. Answers (1)
- List four factors that influence the cost of building work.(Solved)
List four factors that influence the cost of building work.
Date posted: October 11, 2017. Answers (1)
- Explain four factors that may improve reputation of a contractor.(Solved)
Explain four factors that may improve reputation of a contractor.
Date posted: October 11, 2017. Answers (1)