UK Plazma cutter causing SPD failure??

[Andy Y]

I've just had a potentially nasty issue involving a Burnt out, type 2 SPD. My customer has been using a small plasma cutter,
I don't have the exact details of the unit to hand, but it does plug in to a standard 13a socket outlet This is a new 100a single phase TT supply to a small commercial unit.
This was a very close call. The SPD, located directly next to the consumer mainswitch, had burnt out to such a degree, that it has (fortunately) taken out the fuse at the intake.
Is it possible, this cutter could produce enough transient voltage to create this issue?
I was led to believe, these devices should go open circuit when they fail.

 

[Andy Y]

I’m guessing that in that type of single mod SPD that they dont have the soldered joint that melts if any real current for a period is drawn via the now shorted Mov.
You could put the garage on its own supply which is how it should have been done in the first place.

My mention of the garage was just a scenario. This install only has 1 board. I suspect you might be right about the soldered connection, but to my mind, that doesn't make it right.

 

[mainline]

My mention of the garage was just a scenario. This install only has 1 board. I suspect you might be right about the soldered connection, but to my mind, that doesn't make it right.

I suppose analysing the waveform when the plasma cutter is being used is the way forward.
If it's actually bad enough to cause damage to other equipment, then throw it in the bin.

 

[Andy Y]

I suppose analysing the waveform when the plasma cutter is being used is the way forward.
If it's actually bad enough to cause damage to other equipment, then throw it in the bin.

I guess so, it probably does belong
in the bin, I've looked it up & its a good old, generic, Chinese made contraption.

 

[Darkwood]

Are you sure their hasn't been a power surge from a local lightning strike, the plasma cutter may not be anything to do with it, such equipment should by design have its own suppression and smoothing circuitry to eliminate any unnacceptable interference on the power supply.

 

[Andy Y]

Are you sure their hasn't been a power surge from a local lightning strike, the plasma cutter may not be anything to do with it, such equipment should by design have its own suppression and smoothing circuitry to eliminate any unnacceptable interference on the power supply.

That's what I was thinking. It's not like this cutter was running for any great length of time either. Definitely no lightning strikes in the area though.

 

[UKMeterman]

Check the supply voltage is in spec, may need a voltage recorder.

 

[Andy Y]

Check the supply voltage is in spec, may need a voltage recorder.

Maybe there could be issues, it's part of a new build estate of small units

 

[UKMeterman]

TT supply, was it the L - N SPD that burnt or the L-E device?

 

[Andy Y]

TT supply, was it the L - N SPD that burnt or the L-E device?

It looked like the live connection side ( internally) burned against the neutral of the main switch