IEEE 1036-2010 pdf free download – IEEE Guide for Application of Shunt Power Capacitors.
5.2 Related capabilities
5.2.1 Operating and ambient temperatures Capacitors are designed for switched or continuous operation in outdoor locations with unrestricted ventilation and direct sunlight under the maximum ambient temperatures for each mounting arrangement shown in Table 4.
5.2.1.1 Minimum ambient Capacitors are designed for continuous operation and switching operations at temperatures not lower than –40 ° C. The capacitor manufacturer should be consulted for operation below –40 ° C.
5.2.1.2 Effect of temperature It is essential that consideration be given to the arrangement of capacitors and complete equipment as an installation to provide adequate ventilation and dissipation of heat. Capacitors are designed to operate at a lower temperature rise than most other types of apparatus for the following specific reasons: a) Unlike most other power apparatus, shunt capacitors (whether unswitched or switched) normally operate for relatively long periods of time at full load and, therefore, do not benefit from the lower average temperature rise characteristic of typical daily load cycles. b) Capacitors are designed to operate at comparatively high dielectric stresses. The combination of these stresses with operation at high temperature for extensive periods of time will result in gradual deterioration and shortened life.
5.2.1.3 Design considerations Capacitor ratings are based on maximum ambient temperatures with an allowance for heat dissipation by radiation and convection. The arrangement and mounting of capacitors and the conditions of installations will affect the heat dissipation and thereby limit the ambient temperature in which capacitors may be operated. Capacitors and capacitor equipment operating outdoors in direct sunlight and with unrestricted ventilation will normally operate with lower temperature rise than those operating indoors in still air.
The following points are important in relating the operating temperature of a capacitor to the conditions of installation:
a) An individual non-enclosed capacitor, such as is mounted on an outdoor pole, will dissipate heat with the least temperature rise (the heat dissipation being approximately 45% by radiation and 55% by convection).
b) The mounting of capacitors in rows side by side or in tiers, or both, increases the temperature rise because of heating of the air stream and because of reduced radiation.
c) The enclosing of capacitors in a housing or room without forced air ventilation increases the temperature rise because of reduced radiation and restriction of the natural circulation of air.
d) Capacitors subjected to radiation from the sun or from any surface, the temperature of which is above the ambient, show a higher temperature rise.IEEE 1036 pdf download.