IEEE 1115-2014 pdf download

IEEE 1115-2014 pdf download.IEEE Recommended Practice for Sizing Nickel-Cadmium Batteries for Stationary Applications.
4. Defining loads
4.1 General considerations
The duty cycle imposed on the battety by any of the conditions described here will depend on the dc system design and the requirenkilts of the installation, The battery must supply the de power requirement when the fol lowing conditions occur
a) The load on the & system eseeeds the maximum output of the battery charger.
b) The output of the battery charger is interrupted.
c) The ac power is kst (may result in a greater dc power demand than in item b) above).
The most severe of these conditions, in terms of battery load and duration, should be used to determine the battery sue for the installation,
4.2 Load classifications
4.2.1 General
The individual tic loads supplied by the battery during the duty cycle may be classified as continuous or flOflC*)fltiflUOUs,
4.2.2 ContInuous loads
Continuous loads arc energiied throughout the duty cycle. These loads are those normally carried by the battery charger and those initiated at thc inception of the duty cycle. Typical continuous loads are as follow’s:
a) Lighting
b) Continuously operating motors
c) Converters (e.g.. mnverters, dc-dc converters)
d) Indicating lights
e) Continuously encrgiied coils
f) Microprocessor and computer devices
g) Annunciator loads
h) Communication systems
4.2.3 Noncontlnuous loads
Noncontinuous loads arc cncrgicd only during a portion of the duly cycle. These loads may switch on at any lime within the duty cycle and may by on for a set length of time, he removed automatically or by operator action, or continue to the end of the duty cycle. When several loads occur simultaneously within the same shon period of time and a discrete sequence cannut be established, the load should be assumed to be the suni dalI loads occurring within that period. If a discrete sequence can be established, the load the period should be assumed to be the maximum load at any instant. If a load lasts for less than I a, it is normally considered to last for a full second. Typical noncontmnuous loads are as follows:
a) F.mcrgcncy pump motors
b) Critical ventilation system motors
c) Fire pmtcction systems
d) Swirchgear operations
c) Motor-driven vahc operations
f) Isolating switch operations
g) Field flashing of generators
h) Molor.starting currents
i) Inrush currents
Nonconlintbous loads for starting emergency generators, tire pumps, and other equipment powered by internal-combustion engines represent a special sizing case for which the recommended procedures in this document are not well suitccL Annex D covers an industry-standard method for sizing nickel-cadmium batteries for engine-starting duties.
4.2.4 Other considerations
The lists of typical loads appearing in 4.2.2 and 4.2.3 are not a full catalog of the dc loads at any particular installation. Loads applied to the battery are normally typed as constant power, constant resistance, or constant current. However, for sizing purposes, loads arc treated as constant power or constant current. The designer should review each system carefully to be sure all possible loads and their variations are included (see Annex 31.
4.3 Duty cycle diagram
4.3.1 General
A duty cycle diagram showing total load at any lime during the cycle is an aid in the analysis of the duly cycle. To prepare such a diagrani. all loads, expressed as either power or current expected during the cycle. are tabulated along with their anticipated inception and shutdown limes. The total time span of the duty cycle is determined by the requirements of the installation.
4.3.2 Known loads
Loads that have inception and shutdown times that arc known are plotted on the duty cycle diagram as they would occur. If the inception time is known but the shutdown time is indefinite, it should bc assumed that the load will continue through the remainder of the duty cycle.
4.3.3 Random loads
Noncontinuous loads that occur at random should be shown at the most critical time of the duty cycle in order to simulate the worst-case load on the battery. To determine the most critical time, it is necessary to size the battery without the random loath s) and to identify the section of the duty cycle that controls battery size. Then the random load(s) should be superimposed on the end of that controlling section, as shown in Figure I (see also 6.5.5).