How is Medium voltage Metal enclosed switchgear derated for ambient temperatures above 40 degrees Centigrade, for example 45, 50 and 55 degrees Centigrade.

Issue:
Is there a derating for higher ambient tepmeratures associated with Metal enclosed Switchgear?

Product Line:
MV Metal Enclosed Switchgear

Environment:
Application

Cause:
Specifying

Resolution:
Switchgear is derated per IEEE Std C37.20.2-1993 per a formula in paragraph 7.4.1. Per these calculations the deratings for switches are below:

At 45 Deg C 600A derates to 490A / 1200A derates to 980A
At 50 Deg C 600A derates to 472A /  1200A derates to 944A
At 55 Deg C 600A derates to 454A /  1200A derates to 907A

Released for: Schneider Electric USA