IEEE 485-1983 pdf free.IEEE Recommended Practice for Sizing Large Lead Storage Batteries forGenerating Stations and Substations.
IEEE 485 cycle im-posed on the battery by any of the conditionsdescribed herein will depend on the dc systemdesign and the requirements of the installation.The dc power requirements that the batterymust supply occur when:
(1) Load on the dc system exceeds the maximum output of the battery charger
(2) Output of the battery charger is interrupted
(3)Auxiliary ac power is lost (may result ina greater dc power demand than (2) above)The most severe of these conditions shouldbe used to determine the battery size for theinstallation. A diagram of the duty cycle (Fig1)，showing the battery loads in amperes andthe lengths of time for which they must be sup-plied，is normally plotted for this condition.The total time span of the duty cycle is deter-mined by the requirements of the installationand need not exceed the time required to re-duce the battery load to zero.This may be accomplished by restoration of ac power, restoration of battery charger output, or terminationof battery loads.
Load Classifications.The individual dcloads supplied by the battery during the dutycycle may be classified ascontinuousornoncontinuous. Noncontinuous loads lastingone minute or less are designated “momentaryloads’ and should be given special considera-tion (see 4.2.3).
Momentary loads can occur repeatedlyduring the duty cycle but are of short duration,not exceeding 1 min at any occurrence. Al-though momentary loads may exist for only afraction of a second,each is considered to lastfor a full minute because the instantaneousbattery voltage drop for a given momentaryload is essentially the same as the voltage dropafter 1 min. When several momentary loadsoccur within the same 1 min period and adiscrete sequence cannot be established，theload shall be assumed to be the sum of allmomentary loads occurring within that minute.If a discrete sequence can be established,theload for the 1 min period shall be assumed tobe the maximum current at any instant. Typicalmomentary loads are:
(1) Switchgear operations(2) Motor-driven valve operations(3) Isolating switch operations(4) Field flashing of generators(5) Motor starting currents(6) Inrush currents.
The above lists of typical loads are nota full catalog of the dc loads at any one in-stallation.The designer should review each sys-tem carefully to be sure he has included allpossible loads and their variations.For example,it may be desirable to consider the increase ininverter input current with declining inputvoltage.IEEE 485 pdf download.