Handbook of Electrical Installation Practice - BeKnowledge

e taken as to the physical location of the capacitor to avoid problems that could
lead to malfunction of the equipment.
As the maximum working temperature of capacitors is lower than that of other
electrical equipment, any conditions which give rise to unacceptable overloads must
be avoided. This, therefore, stipulates ambient temperature, maximum voltage and
overload current.
Care should be taken in choosing a site for the capacitor to minimise the ambient
temperature. If the site is outdoors, the direct rays of the sun should be avoided,
especially in tropical climates. Rooms housing capacitor assemblies must be adequately
ventilated.
If there are harmonic producers on site, such as thyristor-controlled machines,
then the capacitors need to be located well away from the source of such harmonics,
or designed to cope with any overloads produced in the capacitor by harmonic
currents or voltages.
Because the ambient temperature is an important consideration in the life of any
capacitor installation it is important that it is correctly specified by the purchaser
to the supplier. Three temperature categories are available, as will be seen from
Table 23.6.
Capacitors can be supplied for either indoor or outdoor use. It should be appreciated,
however, that while an outdoor capacitor can be installed indoors, the reverse
is not true.
CAPACITORS AND HARMONICS
Power Factor Correction and Tariffs 653
Table 23.6 Limits of ambient temperature for
capacitor installations (taken from IEC 871-1,
Shunt capacitors for a.c. power systems having a
rated voltage above 1000V and IEC 831-1, Shunt
capacitors of the self healing type for a.c. systems
having a rated voltage up to and including 1000V).
Harmonic distortion in electrical power systems is becoming more and more
prevalent with the ever increasing use of devices having non-linear operating