Accelerated aging of so2 switchgear seals

Partial discharges in SF
₆
-insulated electrical equipment generate gaseous and solid by-products. The gaseous by-products remain in the SF
₆
during operation, reducing its insulation and heat conduction capacities, and causing deterioration of solid material present in the equipment [1]-[3]. These by-products reduce the operational reliability of SF
₆
-insulated equipment and increase the need for maintenance work [4]. It was shown in [5] that some by-products of SF
₆
may interact with the sealing materials of SF
₆
-insulated equipment, leading to gas leaks. A CIGRE study [4] revealed that, between 1991 and 1998, 40% of failures in SF
₆
-insulated high voltage equipment were caused by leaks. IEC 62271-303 [6] stipulates that SF
₆
gas leakage should not exceed 0.5% of the mass of the gas contained in the relevant equipment. Nevertheless, a series of surveys [7] found that the main failure modes of high voltage components in circuit breakers were due to small gas leaks. As a consequence, condition-based maintenance was introduced in the electrical utilities [8], [9] to alleviate the problems caused by gas leaks [10].