Installations that may be vulnerable to these problems are those with low short-circuit power in the High Voltage distribution lines at the low voltage network connection point; or those fed by a power transformer whose K-factor value (harmonic overload factor), by default, is unsuitable for the harmonic contents of the loads it is supplying, or there are long cable sections between the transformer output and the capacitor bank - network PCC, leading to high impedance in this section.
In these cases, the most common effect is an increase in harmonic currents absorbed by the capacitor bank steps. In some cases, such increase may be very serious, severely overloading the capacitors and reactors comprising each detuned filter, and, especially in the case of capacitors, increasing their deterioration, usually in the form of a decrease in capacity. This decrease in capacity even increases harmonic current absorption, because, as can be seen from the formula that determines resonance frequency (Fig. 1), a capacity decrease causes an increase in tuning frequency, meaning it is even closer to the harmonic frequencies in the network (remember that order 5 generally prevails), thereby reducing impedance at that frequency, which therefore increases consumption of currents of that order.
In other words, the detuned filter starts to react in a similar way to a tuned or absorption filter, but, as it is not designed to be used as such, its capacity is exceeded, causing it to deteriorate.
In addition to this effect, the fact that networks with low Scc values, in the event of high harmonic current circulation, usually display high harmonic distortion levels (THD(U)), is another factor leading to an increase in the harmonic current absorbed by capacitors.
In short, any solution that prevents an installed capacitor bank from affecting the network, and, in turn, avoids the capacitor bank itself being affected by the presence of harmonics in the network, may not always solve the problem, with the consequent technical and commercial implications this will undoubtedly entail.