In ring distribution scheme, ________ of a ______ transformer form a loop.

Question

Examoogle · Accepted Answer

The correct answer is Option B: primaries, distribution. In a ring distribution system, the primary windings of several distribution transformers are connected in series to form a closed loop or ring. This configuration allows power to be supplied from both ends of the feeder, enhancing reliability.

Step-by-Step Solution & Concepts:
In a ring distribution system, the primary windings of several distribution transformers are connected in series to form a closed loop or ring. This configuration allows power to be supplied from both ends of the feeder, enhancing reliability.

Working Principle: The ring main system operates by feeding the circuit at one or more points. Because the supply is bidirectional, a fault on any section of the ring only isolates the faulty segment, while the rest of the load continues to receive power from the opposite direction, thus minimizing supply interruptions.

Key Formulas: $V_{drop} \approx I \cdot (r \cos \phi + x \sin \phi)$ — approximation of voltage drop in a distribution feeder; $I_{Total} = I_{A} + I_{B}$ — where $I_{A}$ and $I_{B}$ are currents supplied from two different ends of a ring main

Key Points: Ring systems offer higher reliability compared to radial systems.; Voltage fluctuations at the consumer end are significantly reduced.; Maintenance can be performed on one section of the ring without interrupting the supply to the entire network.

Advantages: Higher reliability of supply; Better voltage regulation; Less copper used for same voltage drop

Disadvantages: More complex protection schemes (directional relays required); Higher initial cost due to switchgear complexity

Applications: Urban residential distribution; Industrial plant power grids; High-density commercial zones

Additional Info: In a radial system, the transformer is fed at only one end, making the system vulnerable to a single fault.. Option A is incorrect because power transformers are typically located at the substation level, not distributed in a ring feeder network.. Option C and D relate to secondaries, whereas ring main topology is defined by the primary interconnection.

Answer: B is correct — in a ring distribution scheme, the primaries of distribution transformers are connected in a loop to ensure redundant supply paths.

Exam Tip: Always remember that ring main systems require directional overcurrent relays to effectively isolate faults, whereas radial systems typically only use non-directional relays.

Examoogle · Answer

Option A: primaries, power

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Option C: secondaries, power

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Option D: secondaries, distribution

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