Fourth CIGRE international reliability survey on equipment operated in 2014-2017

CIGRE periodically conducts an international reliability survey of equipment and examines the lifetime performance to make the best use of existing equipment in power systems. The survey can provide useful information for end-of-life assessment of equipment and good feedback on the validity of international standards under changing network conditions.

The first CIGRE reliability survey collected the data on circuit breakers with different technologies (oil, air-blast, single and double pressure SF₆) operated in the period 1974-1977, which had a significant impact on testing requirements in the IEC standards. The second reliability survey collected the data only on single pressure SF₆ circuit breakers operated in the period 1988-1991. The results were used to consider on lifetime management of circuit breakers. The first and second reliability surveys related to gas insulated switchgears (GIS) were conducted separately in 1990 and 1996.

The third reliability survey collected the data not only on circuit breakers (CB) but also on disconnecting switches (DS), earthing switches (ES), instrument transformers (IT) and gas insulated switchgear (GIS) operated in 2004-2007. The fourth reliability survey further extends the scope to collect the data on generator circuit breakers (GCB), vacuum circuit breakers (VCB), and surge arresters (SA) operated in 2014-2017. The data includes field experience of aged equipment that has been in operation for more than 35 years.

This Technical Brochure provides a general report on the fourth CIGRE reliability survey of various equipment and compares the results with those of the previous surveys. The present results show a generally good service experience with a lower probability of major failures during its lifetime. The average major failure frequencies only for live tank type CB and AIS type IT are increased in the present fourth survey, because some aged equipment (live tank type CB and AIS type IT) with a specific design, which have been in operation for more than 35 years, show an extremely high major frequency in this fourth survey.

Another important trend is that the reliability on switching equipment appears to vary between the utilities in different countries. Therefore, it could provide useful information if CIGRE were to investigate the background information on the reliability and its dependence on the designs, the specifications, the maintenance practices, and operating conditions, while maintaining the anonymity of the utility or the country corresponding to the data.

This fourth survey was the first to collect information on vacuum circuit breakers (VCBs) and metal oxide surge arresters (MOSAs). VCBs, which are used at both MV distribution and HV transmission levels, have generally shown a good performance with a lower probability of failures during its lifetime. MOSAs, which are installed to protect various substation equipment, also...