The GB/T 18802.11 standard explicitly acknowledges the influence of altitude on electrical clearance insulation strength and incorporates this through an "altitude correction factor" in the testing conditions. The standard typically uses 2000 meters as the baseline altitude. For surge protective devices (SPDs) claimed to operate normally at higher altitudes (such as 5000 meters), the testing requirements are more stringent.

Design basis: During the design phase, manufacturers must calculate the correction factor based on the declared maximum operating altitude according to the IEC 60664-1 standard, and accordingly increase all critical electrical clearances within the product.

Experimental Verification: To verify the effectiveness of this enhanced design, standards require that the test voltage used for impulse voltage testing of such SPDs must be multiplied by an altitude correction factor greater than 1, based on the reference test voltage. For example, for an SPD claimed to be suitable for use at 5000 meters, the impulse test voltage must be approximately 25% higher than that for the same model SPD used at 2000 meters. This simulates the reduced insulation strength due to lower air pressure at high altitudes. Only SPDs that can pass this enhanced voltage test can be certified as suitable for the corresponding high-altitude environment. This is a scientific method for verifying the adaptability of the product design by increasing the severity of the input conditions.