What is the effect of increasing the number of sheds on insulator performance in polluted or wet environments?

• A. More sheds decrease surface path and increase field stress.
• B. More sheds lengthen the surface path and reduce electric field stress, improving performance.
• C. More sheds have no effect on performance.
• D. More sheds worsen icing resistance.

Answer: (B)

In polluted or wet environments, the surface path that leakage currents must travel along the insulator is critical. Increasing the number of sheds lengthens this creepage path, which raises the surface resistance the leakage current must overcome. As a result, the voltage drop is spread over a longer route, the peak electric field along the surface is reduced, and the overall surface stress is lowered. This means leakage currents are less likely to cause flashover, so performance improves.

So, adding sheds helps by making the leakage path longer and the field more evenly distributed, which is especially beneficial when contaminants and moisture create conductive films on the surface. The other ideas don’t capture this effect: it doesn’t shorten the path, it does have a meaningful impact, and icing resistance is not the primary factor addressed by simply adding more sheds.