Comparison: Overhead vs Underground Electrical Systems

What is the main purpose of an electrical distribution system?

To transmit electricity over long distances
To efficiently deliver electricity to end-users (correct)
To generate electricity
To store electricity

Which component is NOT typically part of an electrical distribution system?

Power lines
Transformers
Meters
Generators (correct)

What part of the power system connects the transmission system to the consumers' meters?

Circuit breakers
Fuses
Substations
Feeders (correct)

What is the purpose of transformers in an electrical distribution system?

To increase or decrease voltage levels (D) Signup and view all the answers

What is the function of circuit breakers in an electrical distribution system?

To open or close electrical circuits in case of faults (A) Signup and view all the answers

In a low tension distribution system, what is the role of service mains?

To connect buildings to the distribution system (B) Signup and view all the answers

What is the primary reason for the high cost of an underground system compared to an overhead system?

Cost of manholes and special equipment (A) Signup and view all the answers

What is a key advantage of overhead systems over underground systems in terms of flexibility?

Overhead wires can be effortlessly shifted (D) Signup and view all the answers

What is a notable feature of the appearance of underground systems that is influencing electric supply companies?

Invisibility of distribution lines (D) Signup and view all the answers

Why are faults less common in underground systems compared to overhead systems?

Higher insulation provided in underground cables (C) Signup and view all the answers

How do underground systems differ from overhead systems in terms of fault location and repairs?

Faults are less likely but difficult to repair in underground systems (B) Signup and view all the answers

Which system offers better ease of fault location and repairs due to visible conductors?

Overhead system (C) Signup and view all the answers

Why is there no interference with the underground system in terms of power line currents superimposed on speech currents?

Because the underground system physically separates the speech currents from the power line currents. (C) Signup and view all the answers

What is the main advantage of a radial distribution system over other systems?

Lower initial cost of implementation. (C) Signup and view all the answers

When would a radial distribution system be preferred for power distribution?

When the substation is located far from the load center. (C) Signup and view all the answers

What is a key drawback of a radial distribution system?

The potential for overloading at the end of the distributor nearest to the feeding point. (B) Signup and view all the answers

In which type of distribution system do separate feeders radiate from a single substation and feed the distributors at one end only?

Radial system (C) Signup and view all the answers

Why do power line currents superimposed on speech currents raise the potential of the communication channel to an undesirable level?

Due to the overlapping of speech frequencies with power frequencies. (B) Signup and view all the answers

What is the main purpose of the primary distribution system in an A.C. distribution system?

Operates at voltages somewhat higher than general utilization and handles large blocks of electrical energy (A) Signup and view all the answers

What are the most commonly used voltages for primary distribution?

11 kV, 6·6kV, 3·3 kV (C) Signup and view all the answers

How is primary distribution carried out due to economic considerations?

3-phase, 3-wire system (A) Signup and view all the answers

What determines the voltage used for primary distribution?

The amount of power to be conveyed and the distance of the substation required to be fed (C) Signup and view all the answers

What is the primary purpose of a step-down substation in an A.C. distribution system?

To step down voltage from high transmission levels to around 11 kV (A) Signup and view all the answers

What distinguishes the primary distribution system from secondary distribution system in an A.C. distribution setup?

Primary system operates at higher voltages than secondary system (C) Signup and view all the answers

What is a key disadvantage of the radial system connection scheme of a distribution system?

Consumers experience voltage fluctuations (C) Signup and view all the answers

Why are consumers dependent on a single feeder and distributor in the radial system?

Faults on feeder or distributor cut off supply (B) Signup and view all the answers

In a ring main system, why do the distributors receive supply from different points of the feeder?

To ensure each distributor is fed via two feeders (B) Signup and view all the answers

What happens in the ring main system in the event of a fault on any section of the feeder?

The continuity of supply is maintained (D) Signup and view all the answers

Which feature contributes to the high reliability of the ring main system?

Feeding each distributor via two feeders (D) Signup and view all the answers

Why is the radial system generally used for short distances only?

Due to its limitations and faults cutting off supply (B) Signup and view all the answers