IEEE C37.010b-1985 pdf free.IEEE Standard for Emergency Load Current-Carrying Capability.
IEEE C37.010b Current-CarryingCapability. During emergency periods,operation may be required at higher load curtinthen permitted by the ambient compensation procedure outlined in Section 4.4.3.Underthese conditions all the general considerations for ambient compensation are applicable toemergency loading,with additional considera-tions and limitations as outlined in this section.The limits of total temperature for the cn-cuit breaker will be exceeded under the specified emergency load currents, and these highertemperatures may cause a reduction in the op-erating life of the circuit breaker. Inspectionand maintenance of the circuit breaker are re-quired following each emergency cycle as out-lined in 4.4.4.5.
Conditions for Emergency LoadCurrent-Carrying Capability
(1) Emergency load current-carrying capabil-ity factors can be applied to outdoor circuitbreakers only , as listed in ANSI C37.06-1979,Tables 3,4, and 4A.
These factors can be applied to circuitbreakers used in gas-insulated substations un-til specific standards for that equipment areissued. Circuit breakers used in metal-clad switchgear shall be coordinated with overallapplication limitations of the total switchgear.Load current carrying-capability under variload for these circuit breakers will be covered in American National Standard. AppilicationGuide for Metal-Enclosed Power Switchgear Assemblies.
(2 ) Prior to the application of the emer-gency load, the circuitbreaker current-carryingcircuit,including external connections，shallhave been well maintained and be in an essentially new condition.
(3) Following the emergency period,theload current shall be limited to 95% of Ia, therated continous current as modified by ambient compensation according to 4.4.3，for aminimum of 2 h
(3) Duringand followingan emergencycycle and prior to maintenance, the circuitbreaker shall be capable of one interruption atits rated shortcircuit current.
(4) Circuit breakers operated at temperatureswhich exceed their limits of total temperaturemay experience a reduction in operating life.Mandatory inspection and maintenance procedures are required following this duty in ac-cordance with 4.4.4.5 and as recommendedby the manufacturer.
If the calculation does not provide the emer-gency current desired，then a circuit breakerwith the next higher continuous current rating should be selected.IEEE C37.010b pdf download.