The insulation of modern EHV and UHV lines is designed based on
The insulation of modern EHV and UHV lines is designed based on Switching voltage.
Switching voltage refers to the voltage that appears across the insulator when a circuit breaker or other switching device opens or closes a high-voltage circuit.
The voltage spike that occurs during switching can cause significant stress on the insulation and can lead to partial discharge and other insulation failure modes if the insulation is not designed correctly.
To ensure that the insulation of EHV and UHV lines can withstand the switching stresses, the insulation is designed to have a high level of electrical strength, typically expressed in terms of the withstand voltage of the insulation.
The insulation materials used for EHV and UHV lines are typically highly resistant to electrical stress and are designed to maintain their performance over long periods of time.