Why Are Surge Capacitors Tied to Ground?

[kenneth edmiston]

I have a decent understanding of power factor caps, (far from perfect) but I’m not as clear on surge caps.

Surge caps store transient voltages and discharge back into the system?
Why are they tied to ground?
And do they also provide capacitance in the motor circuit they are tied to providing an offset to inductance?

Thanks

 

[Windadct]

Generally - they just absorb the energy of a voltage spike, and technically discharge back to the system, but this is not a significant issue.

Since the V spikes - could be on a single phase, you want this protection relative to ground.

 

[anorlunda]

Think lightning strikes. They are DC. If you designed the grid, how would you deal with lightning surges?

 

[DaveE]

The transients in power systems that surge capacitors are intended to eliminate are composed of higher frequencies than the 50/60/400 Hz power frequency. So the surge capacitor is selected to provide a low impedance path to ground at high frequencies to divert the surge currents away from the part of the circuit you want to protect. Most higher frequency transients coupled into the power system can be diverted to ground (earth) because they come from external sources, like lightning, for example.