Altitude is very important in the selection of Electrical Equipment. Electrical Equipment in General are designed for an altitude up to 1000 m above sea level. At higher altitudes, the density of air decreases. This results in a decrease in the dielectric properties of air. The dielectric property of air depends on the density, temperature as well as pressure.
At high altitudes, all three parameters decrease. Thus the insulation provided by air decreases. The insulation coordination should be reviewed.
Hence, there is a risk of flashovers and arcs. Circuit breakers and other current interrupting devices should be derated at high altitudes.
The operating altitude should be kept in mind when designing equipment.
Another limitation caused by altitude is in heat dissipation. As the air grows less dense, the heat carrying capacity of air decreases. This results in overheating of the equipment. Thus equipment and components may require larger heat sinks or cooling equipment with increased capacity.