IEEE 1115-2014 pdf free 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 battery by any of the conditions described here will depend on the dc system design and the requirements of the installation. The battery must supply the dc power requirement when the following conditions occur:
a) The load on the dc system exceeds the maximum output of the battery charger.
b) The output of the battery charger is interrupted.
c) The ac power is lost (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 size for the installation.
4.2 Load classifications
4.2.1 General
The individual dc loads supplied by the battery during the duty cycle may be classified as continuous or noncontinuous.
4.2.2 Continuous loads
Continuous loads are energized throughout the duty cycle. These loads are those normally carried by the battery charger and those initiated at the inception of the duty cycle. Typical continuous loads are as follows:
a) Lighting
b) Continuously operating motors
c) Converters (e.g., inverters, dc-dc converters)
d) Indicating lights
e) Continuously energized coils
f) Microprocessor and computer devices
g) Annunciator loads
h) Communication systems
4.2.3 Noncontinuous loads
Noncontinuous loads are energized only during a portion of the duty cycle. These loads may switch on at any time within the duty cycle and may be on for a set length of time, be removed automatically or by operator action, or continue to the end of the duty cycle. When several loads occur simultaneously within the same short period of time and a discrete sequence cannot be established, the load should be assumed to be the sum of all loads occurring within that period. If a discrete sequence can be established, the load for the period should be assumed to be the maximum load at any instant. If a load lasts for less than 1 s, it is ormally considered to last for a full second. Typical noncontinuous loads are as follows:
a) Emergency pump motors
b) Critical ventilation system motors
c) Fire protection systems
d) Switchgear operations
e) Motor-driven valve operations
f) Isolating switch operations
g) Field flashing of generators
h) Motor-starting currents
i) Inrush currents
Noncontinuous loads for starting emergency generators, fire 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 suited. 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 are 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 B).IEEE 1115 pdf download.