Which distribution system is more reliable

Question

Examoogle · Accepted Answer

ring

Explanation: The ring main distribution system is more reliable than radial or tree systems because it provides multiple paths for power to reach the load. In the event of a fault in any section of the distributor, only that faulted section can be isolated while the rest of the system continues to receive supply from the other end of the ring.

Working Principle: In a ring system, the distributor is closed in a loop and fed at one or more points. Because current can flow from both directions to a load point, a fault at any point only requires opening the nearest breakers to isolate the faulty segment, ensuring continuous service to all other consumers.

Key Formulas: $V_{drop} = \sum I_i R_i$ — represents voltage drop in a branch which is minimized in ring systems due to bidirectional feeding.

Key Points: Ring distribution provides dual-path supply to every load point.; Radial systems have only one path, making them prone to total blackout if the main line faults.; Voltage fluctuations are lower in ring mains compared to radial systems.

Advantages: High reliability due to redundant power paths; Less voltage drop at consumer terminals; Greater flexibility for maintenance

Disadvantages: Complex design and protective relaying coordination; Higher initial capital cost due to longer conductor runs

Applications: Urban power distribution; High-density industrial areas; Critical infrastructure facilities

Additional Info: A 'tree' system is essentially another term for a branched radial network, sharing its vulnerability.. Radial systems are used primarily in rural areas where load density is low and economy is preferred over high reliability.

Answer: C is correct — The ring main distribution system provides two-way power supply, significantly increasing service continuity compared to radial or tree systems.

Exam Tip: Always remember: 'Radial' = Cost-effective but low reliability; 'Ring' = Reliable but expensive/complex. Choose based on the critical nature of the load.

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