Lighting strike on property. high ZE and arking when testing.

[Jakegood]

hi,

As the title states. Earlier in the week I was sent to a property to do a routine EICR test. When I arrived at said property I was informed that it had recently been struck by lighting! The lighting had split the roof pearling, and done substantial damage to the roof trusses, before finding its entry point below bathroom window. When performing ZE I was getting reading all over the place from 0.45- 0.87, this is on a TNCS system, which is obviously unacceptable. The test also resulted in arking from the main switch. The Tennant said someone had been out and looked at the 35mm tails to and they were damaged and cut back and re terminated. The only thing I can think of saying is there is damage to the incoming side, and to get in touch with the provider before we do the test. Any advice on how a lighting strike caused this?

 

[westward10]

A lightning strike when it hits a building can pass through the walls to the system cpcs, lightning protection with a main protective bond diverts the strike away from sensitive cpcs to ground.

 

[The Ghost]

Are you sure the person who cut back and re-terminated the tails tightened up properly?

 

[Strima]

Lots of volts and lots of amps during a strike, I would guess there would be substantial damage to electrical equipment including switches and other devices.

 

[Jakegood]

Hi,

Yeah, double checked the tails, all good. It has obviously to with the lighting strike. Just wanted to know why exactly it would cause the arking and the high ZE??. My supervisor just said they had to contact the provider.

 

[plugsandsparks]

were your reading taken on the incoming side of the main switch ?

 

[buzzlightyear]

If it was a lighting strike would the meter be fride crisp and dryed.

 

[Wilko]

Hi - when you asked "how can lightning cause this?" it got me thinking. One on line ref. said av lightning bolt to gnd has 10^^9 Joules of energy. Now that might be total bs, but if it was true that's 1,ooo megawatts for 1 second. More than enough to toast anything it feels like.

 

[Richard Burns]

If you were performing a Ze test then there should be no test current flowing through the main switch and so no arcing. I am assuming the main switch is on during the test.
If test current is flowing through the main switch this would indicate a low resistance path line to earth (or line to neutral if your tester also performs PSCC at the same time) on the load side of the main switch (i.e. within the installation).
I would initially suspect, especially with the tails damage, that the main switch is damaged internally.
The high voltage from the lightning could easily arc across large gaps and cause damage to the copper inside the switch even away from the contact faces.

 

[buzzlightyear]

Me thinks all of the wires would be wielded . in the cu board right down to main cut out

 

[Nigel]

First thing Inwas taught about fault finding is to forget whatever you have been told.

So ignore the lightning. It has no impact on your job.

Speak to the DNO to see what they say and if they say that is the earth younare getting then carry out your periodic inspection and code appropriatly.

 

[Strima]

First thing Inwas taught about fault finding is to forget whatever you have been told.

So ignore the lightning. It has no impact on your job.

Speak to the DNO to see what they say and if they say that is the earth younare getting then carry out your periodic inspection and code appropriatly.

True in a lot of situations however I think sa lightning strike maybe a slight indicator to what faults might be existing on the installation.

 

[Nigel]

True in a lot of situations however I think sa lightning strike maybe a slight indicator to what faults might be existing on the installation.

If it is true and even if it is it has no relevance to the periodic inspection.

 

[Strima]

If it is true and even if it is it has no relevance to the periodic inspection.

I disagree, knowing what sort of damage can occur from a strike you can pay even more attention to that. Same as flood damage I would inspect all circuits however take a closer look at those circuits immediately effected by the flood.

 

[Nigel]

I disagree, knowing what sort of damage can occur from a strike you can pay even more attention to that. Same as flood damage I would inspect all circuits however take a closer look at those circuits immediately effected by the flood.

I don’t follow mate. Your tests should be the same regardless of the issue that ‘may’ have effected it. Either the circuit is safe for continued use or it is not. What further testing would you do following a ligtning strike that you would not do as part of a standard PIR?

 

[Strima]

I don’t follow mate. Your tests should be the same regardless of the issue that ‘may’ have effected it. Either the circuit is safe for continued use or it is not. What further testing would you do following a ligtning strike that you would not do as part of a standard PIR?

On a standard PIR I would hold short of lifting boards to inspect cables etc but in the case of a lightning strike it would be more pertinent to do so especially where known junction boxes are etc. as these would be more susceptible to damage.

 

[Nigel]

On a standard PIR I would hold short of lifting boards to inspect cables etc but in the case of a lightning strike it would be more pertinent to do so especially where known junction boxes are etc. as these would be more susceptible to damage.

I would not be ripping up flooring and floor boards if the cables tested fine. No way.

 

[Nigel]

I actually wouldn’t even if they never tested fine. I would note it on the report and code it.

Finding the fault is an extra after the report has been issued

 

[Strima]

Having dealt with a few sites that have suffered lightning strikes you will find cables that test out fine but have suffered thermal damage and need replacing, often these were within containment that you would not normally remove during a PIR.

If you are aware of the nature of damage in advance then would you not price your PIR accordingly?

 

[Nigel]

Having dealt with a few sites that have suffered lightning strikes you will find cables that test out fine but have suffered thermal damage and need replacing, often these were within containment that you would not normally remove during a PIR.

If you are aware of the nature of damage in advance then would you not price your PIR accordingly?

No. I would always price a report based on the schedule of tests detailed within BS7671 as those are the reports you will be issuing.