What is the purpose of heaters on SF6 storage tanks in some EHV breakers?

The purpose of heaters on SF6 storage tanks in some EHV (Extra High Voltage) breakers is to prevent SF6 gas from liquefying in cold temperatures. SF6 is a gas that exhibits unique insulating properties, making it ideal for high-voltage applications. However, at lower temperatures, SF6 can transition to a liquid state, which would negatively impact its insulating characteristics and could lead to a reduction in system reliability.

By incorporating heaters in the storage tanks, the gas is kept in a gaseous state even in cold weather, ensuring that it retains its effective insulating properties. This is critical for the operation of EHV breakers, which rely on SF6 to perform effectively under various environmental conditions. Maintaining the gas in a gaseous form helps in preventing issues related to dielectric strength and facilitates the smooth operation of the breakers.