Gas discharge tubes in transient overvoltage suppression

[earl of sodbury]

Hi, anybody have any experience using these in AC power lines?

In particular, how I translate the commonly given figures for DC firing voltage and DC holdover voltage into AC applications? Don't want to asume a linear relationship, but do want to specify as close to maximum AC operating voltages (UK 250VAC +/- 10V max) as possible.

As usual manufacturers are ignoring comms....

Also - where best to place them? Shorting to earth from L + N, or across L + N, or both?

Thanks, Sod.

[ak_47_boy]

You want to put them between any line that is not tied to ground and ground. Here in Canada neutral is tied to ground in the breaker box so putting a discharge tube between neutral and ground is pointless.

I have seen then put between hot and neutral since neutral is the same thing as ground anyway. I prefer using ground though, it seams simpler to me since in some places neutral is not tied to ground.

The tube should not trigger at a premature voltage until you get into really high frequencys. I would guess well into the Khz range. You must take into account that 250vac has a peak of 353.5 volts (Vpeak=Vrms*1.414).

[earl of sodbury]

Thanks for that