What are the altitude correction factors for Metal Clad Switchgear?

Issue:
Metal Clad Switchgear operated at altitudes above 1000 m / 3300 ft should be multiplied by correction factors to obtain the desired performance.

Product Line:
MV Switchgear.

Environment:
Metal Clad.

Cause:
To achieve the desired performance from Metal Clad Switchgear.

Resolution:
Switchgear assemblies that depend on air for an insulating and cooling medium will have a higher temperature rise and a lower dielectric withstand capability when operated at altitudes above 1000 m / 3300 ft. For applications at higher altitudes, the rated power frequency withstand voltage (1 min), the lightning impulse withstand voltage (BIL), and the continuous current rating of the assemblies should be multiplied by the correction factors in the following table to obtain the modified maximum limits for dielectric withstand and continuous current.

Altitude (m)	Altitude (ft)	ACF for dielectric withstand voltage	ACF for continuous current
1000	3300	1	1
1200	4000	0.98	0.995
1500	5000	0.95	0.991
1800	6000	0.92	0.987
2000	6600	0.91	0.985
2100	7000	0.89	0.98
2400	8000	0.86	0.97
2700	9000	0.83	0.965
3000	10000	0.8	0.96
3600	12000	0.75	0.95
4000	13000	0.72	0.94
4300	14000	0.7	0.935
4900	16000	0.65	0.925
5500	18000	0.61	0.91
6000	20000	0.56	0.9

Released for: Schneider Electric USA