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Lightning protection


Johandup

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And the thunderstorm season has started on the highveld. 

The first victim was my borehole pump and outside dB. Quite annoying and expensive. The repair guy told me I was no 18 for the week. 

Any good advice on how to protect a borehole pump against surges and strikes would be much appreciated. Photos will help. 

Edited by Johandup
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Is it a single phase pump?

Not that it really matters, but I think a single phase pump is probably more susceptible.

I think you have to consider what is happening during lightning.

Two different earth points are developing a serious voltage in between each other and your pump's winding is the weakest spot of insulation, so it breaks down.

Is the pump motor earth bonded to your house earth?  I doubt it.

Bond an earth from  the pump motor and the borehole casing to your main house earth with at least 6mm copper is what I'd try.

Give the current an alternative low resistance path.

 

 

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16 hours ago, Johandup said:

And the thunderstorm season has started on the highveld. 

The first victim was my borehole pump and outside dB. Quite annoying and expensive. The repair guy told me I was no 18 for the week. 

Any good advice on how to protect a borehole pump against surges and strikes would be much appreciated. Photos will help. 

Type 1 surge protection can also be fitted in the pump DB before the main switch. Type 1 is for lightning. Dehn guards are good ones, but expensive. I use LEAR as they are a bit cheaper.

Also bonding of as much conductive parts around the borehole as possible, normally 16mm2 wire is advisable with even a earth spike knocked in a wet area if possible. All this bonded back to your main earth.

 

 

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@Gerrie, you can't stop lightning with a surge protector. A surge protector is just an installed other weak point. Maybe it'll breach the dam there, maybe not.

Let lightning go the way it wants to go. Do things that make it go around your valuable assets as opposed to through them.

Go with the flow, you are literally farting against thunder.

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The problem is the steel casing on most boreholes makes a super excellent earth spike as it goes right down to the water table. So your problem arises with different potential between  your house earth and the borehole casing. Can they be bonded together? Just speculating, not advise!

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1 hour ago, DeepBass9 said:

The problem is the steel casing on most boreholes makes a super excellent earth spike as it goes right down to the water table. So your problem arises with different potential between  your house earth and the borehole casing. Can they be bonded together? Just speculating, not advise!

The submersible pumps I have seen don't even have a pre-wired earth like the power cables (just a terminal on the casing)

Don't know if they take earthing that seriously..

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1 hour ago, DeepBass9 said:

The problem is the steel casing on most boreholes makes a super excellent earth spike as it goes right down to the water table. So your problem arises with different potential between  your house earth and the borehole casing. Can they be bonded together? Just speculating, not advise!

Now, you're on the right track.

The difference in voltage during a lightning strike will exceed whatever insulation it needs to, to get from A to B or B to A.

The casing, pump and the house main earth ( and your water tower, tin roof & garden fence) should all be bonded together, so the current has an alternate route and that that voltage will never build up sufficiently.

1 minute ago, Richard Mackay said:

Don't know if they take earthing that seriously..

Well, why should they, it is after all very well earthed, just like everyone else they are rightly claiming it is fantastically earthed by it's very nature.

The thing is it is an imported earth very close to another imported earth from the electrical system, and under the right conditions it can be at a very differently voltage to the house earth.

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2 hours ago, DeepBass9 said:

The problem is the steel casing on most boreholes makes a super excellent earth spike as it goes right down to the water table. So your problem arises with different potential between  your house earth and the borehole casing. Can they be bonded together? Just speculating, not advise!

200mm steel pipes go down 30m but the water-table starts at 60m.

A 40ka surge protector must take the surge current from the two live cables down to earth when the right conditions occur.

The problem I have is that this must happen at the same time when a surge is generated by lightning current in close vicinity in a suburban area - a direct strike is fatal). So to ground it from the pump to the column is not going to help much.

I’ll rather take a separate 6mm house earth wire (from the pump body) to the outside db panel’s earth close by (within 3m from the steel column) so the current can go to a ground earth spike with no current (hopefully). As the spike as well as the pipe column are inside a garden the areas is always kept moist. A relay connected to a float switch will ensure that there is always a switch gap except when the pump is running to fill up the tanks. Previously I always kept the panel on to switch it on manually.

I would love to be able to afford a Dehnshield surge protector but at +R3600 each it is very expensive. So I bought much cheaper AcDc mov 40ka protectors and a 100m roll of earth wire. I have rebuilt the db with new 6ka mcbs which will get two surge protectors and it’s own earth spike next to it. I don’t want any current to enter my house db as this circuit is supplied from a very expensive battery inverter setup. And I have been getting funny trips caused by outside surges (aka municipal power).

Fortunately my insurer is covering the replacement costs which is in excess of R18k. But the improvements are for my own pocket. With hindsight I think the original borehole pump installer was dumb. He should have recommended a 4 core cable and Dehn protection but I did not know enough about this topic.

One must realize the Highveld is a very dense lightning strike area.  And we need to go to the extreme to minimise lightning damage. Damages can be googled and it is quite an eye opener.

Edited by Johandup
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I don't think it is neccesarily a good idea for things to have their own earth spike as there will then be potential between the different earth termination points. As I understand it they should be bonded together so they are all at the same potential, and the strike surges will take the shortest way to earth, hopefully caught by the surge arrestors. 

Edited by DeepBass9
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21 minutes ago, Johandup said:

so the current can go to a ground earth spike with no current

If anything your new earth spike makes matters worse.

1 hour ago, Johandup said:

So I bought much cheaper AcDc mov 40ka protectors and a 100m roll of earth wire. I have rebuilt the db with new 6ka mcbs which will get two surge protectors and it’s own earth spike next to it. I don’t want any current to enter my house db as this circuit is supplied from a very expensive battery inverter setup. And I have been getting funny trips caused by outside surges (aka municipal power).

It sounds like you may have multiple imported earths.

Your earth spike and the pump and the casing need to be bonded to the house main earth. ( and all other imported earths). Lightening jumped from the sky to balance out a charge on the planet that may have built up over square km's. It is completing a circuit.  Don't think of earth as a current sink, electricity needs a circuit, the earth is conductor. Current still needs to get from A to B. Current doesn't go into the ground and stop in a pile of electrons, it goes to a place of lower potential.

In your case, the charge wants to get onto (or off) your pump power wiring into (or out of) the ground, so that it can make the circuit to another earth point at lower potential. Having multiple unbonded earths just turns a place into the Germiston junction of electrical track jumping.

Why does it do this? - because once it has broken down your pump's insulation there is a lovely copper connection all the way to the next pitstop. And where is that?

It could be a lovely sub -station earth mat km's away, it could be a neighbor's borehole, who knows? The point is the lighting wants to get onto (or from) your electrical cabling and your pump is the path of least resistance to somewhere else. That aquifer is also a low resistance path to god knows where.

My point is you don't need to know where the road is coming from or where its going, but you do know your pump is playing in the traffic. I am saying give it an alternate copper detour around your pump to where it wants to go and sleep easy at night.

Bond all your earths together and let smooth lane changes happen.

 

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At the risk of laboring a point here is a good example of what I am talking about not importing earths.

I cannot take credit for taking this photo, as it was the diligent eye of a colleague that spotted this.

It looks innocent enough, a farmer has " borrowed" the use of a sub-station fence corner post for his farm gate.

So what.

 

Substation Gate.jpg

Well on the other side of that gate there is a farmer's fence obviously that connects by fence wire to earth half a mile away. What I call an imported earth.

And that sub station is literally built on a very low resistance copper earth mat.

If Farmer Brown is busy opening that gate at when lightning strikes or when a power line faults, say one hand on the farm fence one hand on the his gate, he will become a fuse and die.

However, if there was a copper connection between the farmer's fence and the sub-station fence, (bridging out the gate), he would live.

Now, realize that you can get electrocuted in the middle of nowhere during a lightning opening a gate between two farm nice long farm fences (or even an power line fault).

The earth is a conductor.

 

 

 

 

Edited by phil.g00
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48 minutes ago, sulyc said:

My 2 cents worth I was advised to install:

https://nistcontrol.com/product-category/1-phase/ 

to protect my pump 

Nothing wrong with these (if they work), they afford a host of other protections and have been around in different forms for many years.

They won't cover you for lightning though.

My experience using a different flavour of the same thing, (several of them).

I used this type of relay after I found the two probe dry borehole protection unreliable.

I stopped using them on my 380Vac ( I changed later to 220Vac) boreholes ( +/-20 years ago), in favour of simple run-time timers, (set conservatively).

I set these, once I understood my boreholes' year round capacities.

Why because? I burn't out my 3 phase motors, I think by mostly by single phasing. ( Eskom issues).

I felt if they couldn't be relied on to protect for phase failure ( which was claimed), they would be pretty crap at fulfilling their other more subtle claims.

Anyway, a lot less problems using a single phase motors and simple timers and earthing like I propose.

KISS.

No pump issues in years, touch wood.

Edited by phil.g00
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