What is the primary function of the SF6 differential alarm system on an EHV breaker?

The primary function of the SF6 differential alarm system on an Extra High Voltage (EHV) breaker is to monitor the pressure of the sulfur hexafluoride (SF6) gas used as an insulating and interrupting medium. When there is a pressure imbalance, which can indicate a leak or an issue with the integrity of the gas, the system activates an alarm and may also initiate a trip of the breaker to protect the equipment and maintain safety.

Maintaining the correct pressure of SF6 is critical because a significant drop in pressure can compromise the breaker's ability to operate effectively. By sending alarms or tripping the breaker in response to pressure imbalance, the system ensures that any potential failure is addressed promptly, thus preventing damage to the electrical infrastructure and enhancing the overall reliability of the substation's operations.