GB/T 24276-2025 A method of temperature-rise verification of low-voltage switchgear and controlgear assemblies by calculation

Scope

This document specifies a method for calculating the air temperature rise inside the enclosures of low-voltage switchgear and controlgear, or similar products that comply with their respective standards. This method is primarily applicable to enclosed switchgear or switchgear units with no forced ventilation. The document still provides some technical guidelines for adjusting this method and applying it to forced ventilation. The results obtained by using this method are directly influenced by the accuracy of the power loss assessment, which is used as input for the heat calculation. Note: The air temperature inside the enclosure is equal to the ambient air temperature outside the enclosure plus the air temperature rise generated by the power loss of the equipment installed inside the enclosure. When using this method, the maximum daily average ambient air temperature at the installation location of the switchgear is between 10°C and 50°C. The maximum daily temperature should not exceed the maximum daily average temperature by more than 5 K. Several appendices in this document provide guidance on how factors not considered in the calculation method of this document affect the temperature rise inside the switchgear. For example, when the switchgear is subject to solar radiation. In this case, a verification method different from the one described in this document is used to ensure clear results and validation of the design.

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