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

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

CTA-ID : 2019067
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