Temperature rise is defined as the average temperature rise of the ASSEMBLY above the Ambient Air Temperature, when the ASSEMBLY is loaded at its Rated Current with Diversity factor for 8 hours or till it Reaches constant value with variaton less than 1 K/h.
For conducting any Test on the ASSEMBLY, Ambient Air Temperature should be measured during last quarter (15 minutes before the Test), it can be computed by means of two or more thermometers or thermocouples equally distributed around the ASSEMBLY at half its height and at a distance of 1 meter from the ASSEMBLY. As per IEC 61439.
While computing the Ambient Air Temperature, the temperature measuring devices shall be protected against air currents and heat radiations.
Temperature Rise Test is also known as Heat Run Test.
Each Components used in ASSEMBLY, like ACB, MCCB, Fuse, Busbar etc, produce heat due to resistance and Watt loss of the Switchgear & Busbar. When these components are installed inside the Panel with Specefic IP degree, like IP54, IP42, etc, Temperature inside the Assembly increased above Ambient Air Temperatuer outside the panel.
Because of Temperatuer Rise above Ambient,
1) Either, Switchgear Current Carrying Capacity reduces than its Rated current, which is defined at 40°C Reference Ambient Air Temperatue, While Panel Temperatuer Rise is limited to Tested value.
2) OR, Temperatuer insie the Panel Increased than Tested Value, if Swithgear and Busbar are carring their Rated Current continiously.
Due to both of Above, Life of the equipment reduce, Ageing of Insulating components inside the panel may cause adverse impact.