What is the most common cause of failure of overhead line insulators?

What is the most common cause of failure of overhead line insulators? Correct Answer Flashover

Failure of overhead line insulators due to mechanical stress is rare because defective pieces are separated during routine factory test. Failure due to porosity and improper vitrification is also very low. The most common cause of failure of overhead line insulator is flashover.

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What is the main cause for the failure of overhead line insulators?
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