IEEE Std C37.82-2017 pdf download – IEEE Standard for the Qualifcation of Switchgear Assemblies for Class 1E Applications in Nuclear Power Generating Stations.
4. Service conditions 4.1 General The service conditions in the application shall be analyzed to determine if signifcant aging mechanisms are present. An aging mechanism is signifcant if subsequent to manufacture, while in storage, and/or in the normal and abnormal service environment, it results in degradation of the equipment that progressively and appreciably renders the equipment vulnerable to failure to perform its safety function(s) under design basis event conditions. Potential signifcant aging mechanisms include the following: a) Wear and tear from routine operation b) Application that is not encompassed by the usual service conditions listed in IEEE Std C37.20.1, IEEE Std C37.20.2, IEEE Std C37.23, or IEEE Std C37.20.3 c) Radiation is in excess of 100 Gy (10 4 rads) equivalent gamma total integrated dose over 40 years d) Other unusual service conditions such as chemical spray or vibration If the equipment has a signifcant aging mechanism, then the mechanism shall be accounted for in the qualifcation program. Aging, as part of the qualifcation program, may be addressed by age conditioning of a test sample prior to design basis event testing. Age conditioning is not required for equipment without signifcant aging mechanisms. NOTE—For switchgear assemblies and components used in typical nuclear power plant applications, wear and tear from routine operation is the only signifcant aging mechanism.
4.2 Usual service conditions 4.2.1 General The values given as usual service conditions represent the anticipated average conditions for switchgear assemblies in nuclear power generating stations. These values are recommended for use in generic qualifcation programs and do not imply a derating of the equipment. 4.2.2 Ambient temperature A yearly average ambient temperature of 30 °C with temperature excursions to 10 °C and 40 °C is considered usual. Switchgear assemblies used at ambient temperatures in excess of 40 °C shall be evaluated to determine the impact of the ambient temperature on the qualifed life. A thermal aging analysis shall be performed on nonmetallic components. The thermal aging analysis shall combine the excessive ambient temperature and the average continuous current loading (see 4.2.10) to determine the impact on the qualifed life of the equipment. 4.2.3 Relative humidity Relative humidity variations between 10% and 90% are considered usual. If the equipment is installed in an environmental where the humidity exceeds 90% then supplemental testing shall be conducted to meet higher humidity conditions. 4.2.4 Altitude Altitudes of up to 2000 m (6600 ft) above sea level for metal-enclosed low-voltage power circuit breaker switchgear and up to 1000 m (3300 ft) for metal-clad switchgear, metal-enclosed interrupter switchgear and metal-enclosed bus are considered usual.