Influence of age on the reliability of high voltage equipment

CIGRE WG A3.06 is undertaking a survey of reliability and failures of high voltage equipment in service. The time period covered by the survey is 2004 - 2007, and the equipment types under consideration are circuit breakers, disconnectors/earthing switches, instrument transformers and gas insulated substations. The information collected so far has been examined with the purpose of assessing the effect of age, or more precisely: the year of manufacture, on the failure characteristics. It appears that single pressure SF6 circuit breakers manufactured after 1994 shows only a slightly lower major failure rate than older ones. Thus, puffer breakers of the first generation appear not to have reached the end of their service life yet. The major failure rates for disconnector and earthing switches are strongly correlated with age. Equipment more that 30 years old have failure rates that are around five to ten times higher than recently installed equipment. Instrument transformers failure rates generally show little correlation with year of installation. However, one exception exists ; old capacitive voltage transformers have a higher failure rate. Gas insulated substations manufactured after 1994 have substantially lower major failure rates than those manufactured earlier. Quantitative results and more detailed assessments will be available after the survey has been completed and all the collected information has been analysed.