Consumer Unit I would be interested in your sage comments

Mike Johnson · Mar 12, 2020

Thanks for your input pc1996.

"I'm not sure parallel operation works well - whichever device conducts first will get most of the current and eventually blow, so you just delay the replacement. If you can afford to get a type 1+2, or to save a bit of money if you have working type 2 just now then put a type 1 fist and then some inductance before your type 2."

I also am not sure that parallel operation will work effectively, I will let you know next time it get's hit

will be interesting to see what one goes first, if at all with it being a domestic situation on a TT earth I thought a type 2 would be sufficient.

pc1966 · Mar 12, 2020

That ebay device is so cheap it bothers me. Did you try a 500V insulation test on it to see if it does anything at all to limit the voltage?

Mike Johnson said:
I also am not sure that parallel operation will work effectively, I will let you know next time it get's hit will be interesting to see what one goes first, if at all with it being a domestic situation on a TT earth I thought a type 2 would be sufficient.

Time will tell...

Also I'm curious about a TT earth if you are fed by SWA cable, is it not used as an TN style of earth as well? Also when your Hagar module burned out, was it typically the same one each time (e.g. one particular phase to N, or N-E)?

If you do look to putting in a type 1 then cheapest on CEF is the Cudis SPD-3PNECI-25 currently at £380. Has dual terminals for "Kelvin type" wiring which helps at little to keep peak volts down.

If making some inductors then you might be best to get one of the 3m "flexible tails" kits that Doncaster cables do (19-strand wire instead of the traditional 7-strand) to allow the winding of 4 coils for L1-L3 & N as each 2-turn coil needs around 70cm cable plus enough to connect it up, so four 1.5m lengths cut from two 3m would be OK. Need to label them of course, and also make sure the coils are all wound & mounted in the same direction (for good common-mode impedance), but ideally each staggered and separated a bit to lower magnetic interaction and provide more cooling.

Putting any impedance in the earth is just a bad idea in my book!

Mike Johnson · Mar 12, 2020

All rural supplies in France are TT.

Problem with knowing what protector went is that it happens mostly when we are not there and by time I get there they are all blown, so unless they all go at once, I don't know which one went first.

pc1966 · Mar 12, 2020

Mike Johnson said:
All rural supplies in France are TT.

What is done with the armour of the SWA then? Do you ground that also to your TT rod, or is it left unconnected?

More and more it sounds like you need a type 1 protector for that sort of rural site.

The difference in energy handling is big, as the typical 12.5kA rating for the 10/350us pulse is like 100kA or more for a 8/20us pulse. Also most type 1 SPD use a GDT instead of (or sometimes in series with) a VDR for higher handling capacity, so if coordinating with a type 2 then that extra inductance is really important so the 1st device reaches its spark-over value before the downstream VDR is trying to gobble much of the surge.