Q2Power System - I
Question
Q.2. Why we use Vacuum Circuit Breaker in High Transmission System and not Air Circuit Breaker?
Answer
Vacuum circuit breakers are preferred over air circuit breakers in high-voltage systems because vacuum offers far superior dielectric recovery and arc-quenching capability with minimal contact erosion and maintenance, allowing compact, reliable interruption at high voltage/current levels that air breakers cannot match economically.
Vacuum, being the near-perfect insulating medium (extremely high dielectric strength, since there is virtually no gas to ionize and sustain an arc), allows a vacuum circuit breaker to interrupt current with very short contact gaps, minimal contact erosion, and negligible maintenance over its service life, all in a compact sealed unit. Air circuit breakers, by contrast, require much larger physical size, more complex arc-chutes/splitters to elongate and cool the arc in open air, and are subject to significant contact wear and higher maintenance, making them impractical and uneconomical at the higher voltage and fault-current levels of high-transmission systems, where vacuum (or SF6) breakers offer superior performance in a much smaller footprint.