Previous Year Question

Correct Answer

C — the thermal limit of current carrying conductor

Concept and Reasoning

A DC transmission conductor has no AC stability or reactive-power limit of the same type as an AC line. Its continuous power-transfer capability is therefore mainly constrained by allowable conductor current and temperature—that is, the thermal current-carrying limit.

Calculation / Key Relation

Pdc=Vdc Id

Id,max set primarily by conductor thermal rating

Exam Takeaway

For a DC line, think current heating when asked the basic power-carrying limit.

Common Mistake

Do not import AC steady-state stability or reactive-power limits into a simple DC-line question.