Undercurrent Protection In 5th Harmonic Filter

[Keegan Howe]

Is anyone able to explain the purpose of undercurrent protection in a 5th harmonic filter.

With reference with the attached schematic, why are the highlighted CTs installed in the resistance circuit of the filter and why would a low current in this circuit cause a fault condition? Is it just to ensure that the resistors have not opened circuited?

 

[krisys]

In my view an alarm should be good enough for the resistor open condition. This is a damping resistor to absorb the surges. So monitoring the availability of these resistors is very crucial. But it need not trip immediately. The filter can be shut down manually.

Again, ff the installation is un-attended, better trip rather than going unattended!