At higher altitudes, atmospheric pressure
decreases. Since most of the atmospheric
molecules are held close to the earth’s
surface by the force of gravity, air pressure
decreases rapidly at first, then more slowly
at higher levels. Hence air becomes thinner
at higher altitudes and cannot be as effective
an insulator leading to derating of the
equipment.
At higher altitudes, even the auxiliary
components for the operating mechanisms
like motors insulation are stressed