IEEE C37.37-1979 pdf free.An American National Standard de for AC High-Voltage Air Switches(in excess of 1000 volts)
The allowable continuous current of an airswitch is based on the allowable maximumtemperature of the air switch parts and is affected by the ambient temperature.By utiliz-ing the formula in 4.5.1 of ANSI/IEEE C37.30-1971 and Table 3 of ANSI/IEEE C37.30-1971(Table 1 herein)， the loadability factorof each switch part class (see 4.2 below) atvarying ambient temperatures may be deter-mined. The loadability factors are listed inTables 2 and 3.Figs 1 and 2 (light and heavylines) are graphical presentations of Tables 2and 3.
An air switch is made up of a number of different switch parts. For purposes of this guidethese parts are classified and grouped in accordance with their material and function intoswitch part classes，each of which is given aswitch partclassdesignation. (See ANSI/IEEEC37.30-1971，4.5.3.) The loadabilityfactors of each switch part class，as a functionof ambient temperature，are represented by acurve，such as Co3 of Fig 1.The point C isthe loadability factor at 6o°C ambient; thepoint o is the loadability factor at 25°Cambient; and the point 3 is the loadability factor at —30C ambient. Curves intersect at o(1.22 loadability factor at 25°C ambient).
AllowableContinuous Current Class(ACCC) Designation
The AcCC designation of an air switch is acode which identifies a composite curve madeup from the limiting switch part classes. (SeeANSI/IEEE C37.30-1971，4.5.4.)Forex-ample: for a nonenclosed air switch when com-bining switch part classes DO4 and FO6, theAccc designation for the switch becomes Do6(see Fig 1, heavy line DO6).
Ailowable Continuous Current Capabil-ity. The allowable continuous current capabil-ity of an air switch at a given ambient tempera-ture is equal to the loadability factor at that ambient temperature multiplied by rated con-tinuous current of the switch. For example:a 1200-A nonenclosed switch with ACccdesignation DO6 has a loadability factor LF=1.47 at—10°C and, therefore, has an allowablecontinuous current capability of 1764 A (seeFig 1).Interrupter switches.This guide does notimply a relationship between the allowablecontinuous current capability and the inter-rupting capability of interrupter switches.Forinterrupting capabilities of interrupter switchesat higher than rating, or at ambients other thanthe range specified for the interrupter switch,consult the manufacturer.IEEE C37.37 pdf download.