30 Questions
What is the main purpose of an electrical distribution system?
To efficiently and safely deliver electricity to end-users while ensuring reliability and stability of the system.
What are the components of an electrical distribution system?
Power lines, transformers, circuit breakers, fuses, and meters.
Define an electrical distribution system.
A network of electrical components used to supply power to buildings, homes, and industries.
What is the role of transformers in an electrical distribution system?
To step down high voltage electricity received from the power generation station to lower voltage levels for distribution.
What does the distribution system consist of?
Feeders, distributors, and service mains.
Where does the distribution system receive high-voltage electricity from?
Power generation stations.
What makes the underground system more expensive compared to the overhead system?
The high cost of trenching, conduits, cables, manholes, and special equipment.
Which system, overhead or underground, is more flexible?
Overhead system.
Why are faults in underground systems considered rare?
Cables are laid underground and are generally provided with better insulation.
What contributes to the better appearance of underground systems?
All distribution lines are invisible in underground systems.
What is a disadvantage of underground systems when it comes to fault location and repairs?
Difficult to locate and repair faults.
How does the current carrying capacity and voltage drop compare between overhead and underground systems?
Not provided.
What is a 2-wire DC system used for in distribution?
For low power distribution of DC power
Explain the difference between the outgoing and return wires in a 2-wire DC system.
One is the positive outgoing wire and the other is the negative return wire.
What is the main advantage of a 3-wire DC system over a 2-wire system?
It provides two voltages at the consumer terminals: V between any outer and the neutral, and 2V between the outers.
Why are lamps and heating circuits connected between either outer and the neutral in a 3-wire DC system?
Because they require less voltage compared to loads like motors, which are connected across the outers.
Name two methods of obtaining a 3-wire DC system.
- Two generator method. 2. 3-wire DC.
Why is the 2-wire DC system never used for transmission purposes?
Due to its inefficiency for transmission purposes.
What are the two types of distribution systems based on the nature of current?
D.C. Distribution System, A.C. Distribution System
Why is the overhead system more commonly used for distribution?
It is 5 to 10 times cheaper than the equivalent underground system.
Name the three schemes of connection in a distribution system based on connection.
(a) radial system, (b) ring main system, (c) interconnected system
What is the main advantage of using alternating current in distribution systems?
Alternating voltage can be conveniently changed in magnitude by means of a transformer.
In what situations is the underground distribution system typically used?
It is used where overhead construction is impracticable or prohibited by local laws.
Why is alternating current preferred over direct current in modern distribution systems?
AC voltage can be easily transformed, allowing for efficient high-voltage transmission.
What are the limitations of the radial system connection scheme in a distribution system?
Consumers are dependent on a single feeder and single distributor, leading to supply cut off in case of faults.
Describe the ring main system connection scheme in a distribution system.
The primaries of distribution transformers form a loop that starts from the substation, makes a loop through the area to be served, and returns to the substation.
What advantage does the ring main system offer in terms of supply reliability?
The system is very reliable as each distributor is fed via two feeders.
How does the ring main system prevent voltage fluctuations at consumer's terminals?
By having less voltage fluctuations at consumer's terminals.
Explain how supply continuity is maintained in the ring main system in case of a fault.
In the event of a fault on any section of the feeder, the supply continuity is maintained as each distributor is fed via two feeders.
Provide an example scenario where the ring main system ensures continuity of supply in case of a fault.
If a fault occurs at any point F of section SLM of the feeder, the continuity of supply is maintained through the other feeder.
Test your knowledge on substation power distribution systems, focusing on the use of converting machinery like mercury arc rectifiers, rotary converters, and motor-generator sets. Learn about 2-wire and 3-wire DC systems used for distribution at substations.
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