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Harmonics
> Insensitivity of capacitors to harmonics
INSENSITIVITY OF CAPACITORS TO HARMONICS
By design and in compliance with applicable standards,
capacitors are capable of withstanding a continuous rms current equal to
1.3 times the nominal current defined at the nominal voltage and frequency values.
This excess current coefficient has been defined to account for
the combined effects of the presence of harmonics and excess voltage (with the capacitance variation parameter being negligible).
It can be noted that according to the degree of harmonic
interference SH (power of harmonic generators), this coefficient generally proves to be insufficient and that the parameter Scc
(short-circuit power) directly related to the power of the source ST is
preponderant in the value of the parallel resonance frequency (Fr.p.).
By combining these two parameters SH and ST, three types of
networks can be defined with a corresponding "type" of capacitor to be installed:
| Type of supply |
Pollution
criterion |
Type of
capacitor
to be used |
| Low level of
interference |
 |
Standard type |
| Moderate level of
interference |
 |
H type |
| High level of interference |
 |
*SAH type
anti-harmonic reactors
*FH type
harmonic filters |
* SH: expanded power in kVA of
harmonic generators present in the secondary winding of the MV/LV
transformer(s) to be compensated.
* ST: power in kVA of the MV/LV transformer (or MV/LV transformers
for two or more transformers in parallel).
Harmonics
summary
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