throwing a switch on small load has fried equipment !! any advice please !!

[capa666]

Look at the switching rating of the main switch as mentioned before it would be like a AC23 rating etc if as i suspect it is its adequete for switching on load including medium inductive loads then if all other avenues have been drained it sounds like the 'N make first' contact failed to do so and to be honest il be supprised if a split second difference was the cause with the amount of equipement damaged this sounds like N was off line for quite a few seconds if not longer.

Even if the switch is adequate for load switching its a practice you shouldn't get into doing as you rely on the the switches 'Make N-first' and 'break N-last' as any issue with this may damage sensitive equipment but i see you already realise your error..... even after throwing the main switch on i would always check N is present before bringing the loads on line.
Obviously we are discussing a 4pole device here as 3pole pose lesser risk as long as they are adequate for load switching.

hi Darkwood, the neutral is in a fixed terminal so was never disconnected, the links are tight and connection !!!

does this help any more ??

 

[capa666]

Sorry to jump in, but if you where diing your final tests did you do your live tests before loading the phases?


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Hi Simon, this is an ECR we are carrying out, i don't understand what you are saying, the testing is progressive and a large commercial property.

 

[SimpleSimon]

Hi Simon, this is an ECR we are carrying out, i don't understand what you are saying, the testing is progressive and a large commercial property.

Oh sorry I thought this was an installation certificate you where carrying out. My bad.

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[Darkwood]

hi Darkwood, the neutral is in a fixed terminal so was never disconnected, the links are tight and connection !!!

does this help any more ??

Prior to switching on were you testing the Sub-main supply cable, if so did you have a collegue/apprentice at the other end of the cable..... maybe they forgot to reconnect neutral but covered there backs. The reason i ask is with the info given it all points towards a missing neutral when 3ph was re-established and for several seconds at least, had it been a DNO issue the effects would have been seen from every 3ph DB and as you say its a solid neutral 'unswitched' connection then it would seem we are not getting the full story here, the items mentioned all have Selv control or monitoring systems and its the fact that the control boards have burnt out which would take several seconds in some cases as the transformers get hot before melting and failing which rings true regarding some of your posts.

If all the effected items were on only one of the 3-phases its possible the phases didnt close properly but left a small enough gap to arc across this could damage sensitive equipment but only a diagnostics of the failed equipment could establish whether it burnt out with a large sustained voltage (missing neutral effect) or component/chip failure through spiking.

 

[polo1]

cappa666, really sorry to learn of the problems you have had. Unfortunately I have nothing to add to the ideas already floated by Darkwood and others. I do hope you'll let us know how this all pans out, in particular if you find the cause....it's certainly got me thinking. All the best!