Eaton's Power factor correction: a guide for the plant engineer states,
Capacitors and transformers can create dangerous resonance conditions when capacitor banks are installed at the service entrance. Under these conditions, harmonics produced by nonlinear devices can be amplified manyfold. Problematic amplification of harmonics becomes more likely as more kVAR is added to a system that contains a significant amount of nonlinear load. You can estimate the resonant harmonic by using this formula:
\$ h = \sqrt {\frac {kVA_{sys}}{kVAR}} \$
kVAsys = short-circuit capacity of the system
kVAR = amount of capacitor kVAR on the line
h = the harmonic number referred to a 60 Hz base
If h is near the values of the major harmonics generated by a nonlinear device—for example, 3, 5, 7, 11—then the resonance circuit will greatly increase harmonic distortion.
Two questions:
Why would resonance depend on the short-circuit capacity of the system? (Can you explain the formula?)
I can't find a similar equation for 50 Hz. Any suggestions?
For reference, this is for a 1 MVA transformer (short-circuit capacity not known at this time) and 350 kVAr PF bank).