Electricity (and Shocks)

[Tywais]

I'd be careful about using salt water to "enhance" an earth. What this will do is advance the rate of corrosion

& eventually, cripple the earth.

Yep, salt will corrode the copper pretty quickly, especially a problem with copper clad ground rods. There are specific electrolytes (chemicals) made for this purpose.

[david96]

I can see a 3 phase, about 100 kVA transformer quite clearly from my balcony, no N-E link

Interesting, scary even.

There was a post a while back from a chap who evidently had a phase grounded somewhere in his building (a row of shophouses IIRC). He was seeing 220V ground to neutral and 380V or so ground to live, obviously if the neutral-ground link was fitted this would have caused some fireworks.

Sooooo, maybe we have stumbled upon a very worrying design fact.

EDIT Any of the electrical pro's seen this / comments??

I have never seen neutral bonded to earth at the transformer in Thailand, it may be earthed on the LV supply network at one or more points with a 16sqmm bare stranded copper conductor.

Another point, can any one quote in English the clause in the Legislated Thai wiring regulations where the MEN system is now mandatory, eg "the consumers installation shall have the neutral connected to the main earth conductor at the main switchboard."

And remember verify the neutral visually and carry out polarity tests before connecting to supply.

[Naam]

And yes Naam, you don't make silly comments BUT.....

I'd be careful about using salt water to "enhance" an earth. What this will do is advance the rate of corrosion

& eventually, cripple the earth.

better some corrosion than stepping into the shower and get jolted (my experience in the african bush) anyway, how long does it take for an 18mm copper rod to be eaten up by salt? will i live that long?

what i don't understand is "cripple the earth" Kangorito. please explain.

[elkangorito]

And yes Naam, you don't make silly comments BUT.....

I'd be careful about using salt water to "enhance" an earth. What this will do is advance the rate of corrosion

& eventually, cripple the earth.

better some corrosion than stepping into the shower and get jolted (my experience in the african bush) anyway, how long does it take for an 18mm copper rod to be eaten up by salt? will i live that long?

what i don't understand is "cripple the earth" Kangorito. please explain.

With pleasure "Dr" Naam.

Without going into a lengthy explanation, the impedance from the furthest earthed point (at a power point for example) to the earth electrode must be less than a "certain" value. Any corrosion will increase this value & thereby allow a "voltage drop" to occur between the furthest earthed point & the electrode. This may present itself as a potentially lethal voltage (above 50v RMS or 120v "ripple free" DC) in the ground, near the main earth electrode, which is directly dependant upon this "earth fault loop impedance".

[gharknes]

get the building maitenance man to install a ground and new outlet all he has to do is drill hole in the floor and put a metal plug with a wire attached to it for the ground and you will have a 3 way plug look like this

Er, speaking as the only "Bull Powered Member" of Thaivisa I feel qualified to comment that the above is pure Bull of the highest order.

Drilling a hole in the floor as a ground is useless, concrete is a pretty good insulator unless it's wet (then you have other problems with your plumbing). A ground MUST go to a proper ground rod buried in the ground, period!!

not quite correct, if you can get your condo floor etc tied to the same potential as the negative supply then effective grounding in your immediate area is accomplished, yes true ground is in the ground but this only works if it is provided throughout the building, it's all relative to what you choose as "ground"

[gharknes]

PS a possible option for earthing would be to fit a short copper pipe to part of your water system, but this would depend on your water supply and will only work while there is water in the system.

[Crossy]

not quite correct, if you can get your condo floor etc tied to the same potential as the negative supply then effective grounding in your immediate area is accomplished, yes true ground is in the ground but this only works if it is provided throughout the building, it's all relative to what you choose as "ground"

I think you're getting confused with the notion of 'equipotential bonding'. There is no way that connecting your ground wire to an insulator (concrete) is going to have any effect whatsoever.

However you may choose to explain how this works if you wish. Please use technical language if necessary, although I only have a Batchelor's Degree in Electrical and Electronic Engineering (Bath 1982) there are plenty of Masters and Doctors on this board who will help me with the harder sums.

BTW MY domestic supply is AC and therefore does not have a 'negative' side, perhaps you have DC mains in your country.

PS a possible option for earthing would be to fit a short copper pipe to part of your water system, but this would depend on your water supply and will only work while there is water in the system.

OK, another one you will need to explain. I'm assuming you're advocating the fitting of a short copper pipe into an otherwise PVC system. Since water is also a pretty good insulator unless quite impure (considerably more impure than the stuff that comes out of the tap), you're going to have to explain how this can have any effect.

Thankyou for your time

[Naam]

And yes Naam, you don't make silly comments BUT.....

I'd be careful about using salt water to "enhance" an earth. What this will do is advance the rate of corrosion

& eventually, cripple the earth.

better some corrosion than stepping into the shower and get jolted (my experience in the african bush) anyway, how long does it take for an 18mm copper rod to be eaten up by salt? will i live that long?

what i don't understand is "cripple the earth" Kangorito. please explain.

With pleasure "Dr" Naam.

Without going into a lengthy explanation, the impedance from the furthest earthed point (at a power point for example) to the earth electrode must be less than a "certain" value. Any corrosion will increase this value & thereby allow a "voltage drop" to occur between the furthest earthed point & the electrode. This may present itself as a potentially lethal voltage (above 50v RMS or 120v "ripple free" DC) in the ground, near the main earth electrode, which is directly dependant upon this "earth fault loop impedance".

ok Kangorito. now i understood. initially i took the "crippled earth" literally (meaning "crippled soil" around the rod).

[naka]

And yes Naam, you don't make silly comments BUT.....

I'd be careful about using salt water to "enhance" an earth. What this will do is advance the rate of corrosion

& eventually, cripple the earth.

better some corrosion than stepping into the shower and get jolted (my experience in the african bush) anyway, how long does it take for an 18mm copper rod to be eaten up by salt? will i live that long?

what i don't understand is "cripple the earth" Kangorito. please explain.

An earthing rod is typically a solid mild steel rod with a thin copper coating.

Naka.

[gharknes]

not quite correct, if you can get your condo floor etc tied to the same potential as the negative supply then effective grounding in your immediate area is accomplished, yes true ground is in the ground but this only works if it is provided throughout the building, it's all relative to what you choose as "ground"

I think you're getting confused with the notion of 'equipotential bonding'. There is no way that connecting your ground wire to an insulator (concrete) is going to have any effect whatsoever.

However you may choose to explain how this works if you wish. Please use technical language if necessary, although I only have a Batchelor's Degree in Electrical and Electronic Engineering (Bath 1982) there are plenty of Masters and Doctors on this board who will help me with the harder sums.

BTW MY domestic supply is AC and therefore does not have a 'negative' side, perhaps you have DC mains in your country.

PS a possible option for earthing would be to fit a short copper pipe to part of your water system, but this would depend on your water supply and will only work while there is water in the system.

OK, another one you will need to explain. I'm assuming you're advocating the fitting of a short copper pipe into an otherwise PVC system. Since water is also a pretty good insulator unless quite impure (considerably more impure than the stuff that comes out of the tap), you're going to have to explain how this can have any effect.

Thankyou for your time

Perhaps you can do a little experiment for me then, in your bare feet touch the live pin of your mains - then when you have survived that, run the water tap and do same, let us know how you get on ***flame removed***

oh and just so everybody can learn from your vast knowledge, is the AC alternating between 0 and 240v or -120 to +120, and just to add another question - is ground the same potential as the negative side of the mains, if you survived please explain

Edited December 16, 2007 by sbk
no flaming--sbk

[Crossy]

Perhaps you can do a little experiment for me then, in your bare feet touch the live pin of your mains - then when you have survived that, run the water tap and do same, let us know how you get on ***flame removed**

oh and just so everybody can learn from your vast knowledge, is the AC alternating between 0 and 240v or -120 to +120, and just to add another question - is ground the same potential as the negative side of the mains, if you survived please explain

Why do these threads always degenerate into flame wars, particularly when someone (you) posts faulty or downright dangerous advice? You have not demonstrated how your grounding techniques work, rather you have resorted to insulting fellow board members.

I'm not going to get hold of the live pin of anything because I'm not stupid, although I have no doubt that I would PROBABLY survive (I've survived far worse shocks in my life, I don't really want to push my luck), this does not demonstate anything about grounding.

The 220V AC supply alternates between approximately +311V and -311V fifty times a second.

The ground is at approximately the same potential as the NEUTRAL of the supply (the mains does not have a negative side) as the neutral is connected to ground at the transformer and by the MEN / PME link in your consumer unit.

It is painfully obvious that you are lacking in basic electrical knowledge. I am not going to continue to bite on this subject, sorry.

[sbk]

Lets not degenerate into name calling please.

Please keep it civil, thanks.

[Naam]

And yes Naam, you don't make silly comments BUT.....

I'd be careful about using salt water to "enhance" an earth. What this will do is advance the rate of corrosion

& eventually, cripple the earth.

better some corrosion than stepping into the shower and get jolted (my experience in the african bush) anyway, how long does it take for an 18mm copper rod to be eaten up by salt? will i live that long?

what i don't understand is "cripple the earth" Kangorito. please explain.

An earthing rod is typically a solid mild steel rod with a thin copper coating.

Naka.

only technical ignorants would accept that! my earth rod is SOLID copper and i made sure it is because the electrician asked me whether i would prefer the more expensive copper rod.

[Gimbo]

Bear with me as English is not my first language, and I can not recall all the technical words. But I will try to write in a way that I hope will be understood.

When I go outside and look at the power cables running trough the village, the pylons have 3 wires. So assume that this is a 3 phase 380V (400 V) system.

I will call them L1, L2 and L3 (as we do in Norway)

Into the house however we have only 2 wires, connected to L1 and L2. Thus giving us 220 Volts into the house.

Therefore, I assume that the 3 phase system here is a Delta system. With floating ground.

I.e the ground is separately installed and connected to the fusebox (we have a one of these cabinets with Square D atomatic fuses, and the ground is a separate cable from the fuse box to ground by way of a 2meter copper earth rod). And L1 and L2 is hence completely insulated from ground.

This is similar to the system we have in Norway. And it does not have any Neutral. And both L1 and L2 are live.

However in most countries as I have understood it, a Y system is used. Where the distribution system is by way of 4 wires. L1, L2 and L3 plus Neutral (N).

220 Volts is achieved by taking 1 phase power to the house from L1 and Neutral. So in these systems there is indeed a Neutral and a live wire. And If I am correct ground is connected to the N wire at the distribution box in the house.

But here in the village it appears that the Delta system is in use. Since the distribution cabloes in the village only have 3 wires.

Now we have what we in Norway (directly translated from Norwegian) call a earth fault switch, that will automatically trip if there should be a fault, f.ex ground connected to live as a result of failure in an appliance.

We have Grounded outlets in all all rooms.

this should be safe enough or what?

[Tywais]

Please keep it civil, thanks.

An earthing rod is typically a solid mild steel rod with a thin copper coating.

only technical ignorants would accept that! my earth rod is SOLID copper and i made sure it is because the electrician asked me whether i would prefer the more expensive copper rod.

Did you miss sbk's comment? And ground rods are typically copper clad steel for two reasons. Cost and the ability to drive them in without deformation.

[cmsally]

Although you should get it grounded if you can; another measure is to buy one of the extension cords with a fuse built in.

Sometime they are covered by a bit of coloured screw in plastic.

With these if you overload them the fuse will pop before anything else too drastic can happen.

I have one in the kitchen; then everytime a smart person plugs in the microwave at the same time as the small convection oven the fuse blows before any more damage can be done.

I also have a packet of spare fuses!

[Crossy]

Bear with me as English is not my first language, and I can not recall all the technical words. But I will try to write in a way that I hope will be understood.

.....................

Now we have what we in Norway (directly translated from Norwegian) call a earth fault switch, that will automatically trip if there should be a fault, f.ex ground connected to live as a result of failure in an appliance.

Understand fully gimbo, your English is better than my Norgwegian

Every domestic installation I've seen in Thailand has been Y connected, so if you have a delta it's unusual. If you measure the voltage between each pin and ground what do you see?

Are you sure you're looking at the right aerials? The 11/25kV overheads are only 3 wire.

[Crossy]

Although you should get it grounded if you can; another measure is to buy one of the extension cords with a fuse built in.

Whilst the fused extension is a good idea, it is NOT the same as having a proper ground. I hope the extension cord you're using with the microwave has a 3 pin plug

[lopburi3]

Bear with me as English is not my first language, and I can not recall all the technical words. But I will try to write in a way that I hope will be understood.

When I go outside and look at the power cables running trough the village, the pylons have 3 wires. So assume that this is a 3 phase 380V (400 V) system.

I will call them L1, L2 and L3 (as we do in Norway)

Into the house however we have only 2 wires, connected to L1 and L2. Thus giving us 220 Volts into the house.

Therefore, I assume that the 3 phase system here is a Delta system. With floating ground.

I.e the ground is separately installed and connected to the fusebox (we have a one of these cabinets with Square D atomatic fuses, and the ground is a separate cable from the fuse box to ground by way of a 2meter copper earth rod). And L1 and L2 is hence completely insulated from ground.

This is similar to the system we have in Norway. And it does not have any Neutral. And both L1 and L2 are live.

However in most countries as I have understood it, a Y system is used. Where the distribution system is by way of 4 wires. L1, L2 and L3 plus Neutral (N).

220 Volts is achieved by taking 1 phase power to the house from L1 and Neutral. So in these systems there is indeed a Neutral and a live wire. And If I am correct ground is connected to the N wire at the distribution box in the house.

But here in the village it appears that the Delta system is in use. Since the distribution cabloes in the village only have 3 wires.

Now we have what we in Norway (directly translated from Norwegian) call a earth fault switch, that will automatically trip if there should be a fault, f.ex ground connected to live as a result of failure in an appliance.

We have Grounded outlets in all all rooms.

this should be safe enough or what?

I am not sure why you only see three wires but here in Bangkok we have the 3 live wires and a neutral on the poles outside my home and there are two wires feeding home - one is hot and the other is neutral (as a quick check with a neon tester will show. I am sure you have a 230v hot wire and a neutral running into your home. The earth fault switch (RCD) actually detects a difference between the load/hot wire and the neutral wire and does this in a faction of a second to protect life. A normal circuit breaker or high trip current RCD can react to the normal appliance failure and prevent most fires - it is you life that the home RCD is designed to protect. Use the test switch on a regular basis. Grounded outlets are a very good idea and when you have a three prong plug be sure to use it or an adapter that allows it to be grounded.

[Gimbo]

Bear with me as English is not my first language, and I can not recall all the technical words. But I will try to write in a way that I hope will be understood.

.....................

Now we have what we in Norway (directly translated from Norwegian) call a earth fault switch, that will automatically trip if there should be a fault, f.ex ground connected to live as a result of failure in an appliance.

Understand fully gimbo, your English is better than my Norgwegian

Every domestic installation I've seen in Thailand has been Y connected, so if you have a delta it's unusual. If you measure the voltage between each pin and ground what do you see?

Are you sure you're looking at the right aerials? The 11/25kV overheads are only 3 wire.

Pretty sure, as the pylon is about 2 meters from our wall. And from that there is only 2 wires connected to our meter, that hangs on the pylon, and from the meter they proceed into the house and to our "fuse box".

I can take a picture and post tomorrow, when it gets light. Too dark now. Also I dont have a volt meter. Anyway, if I am right and its Delta configuration, I should see 0 Volt, right?

(Iæll buy a volt meter tomorrow also methinks)

[Gimbo]

Was out with the flashlight and had a look again. The neigbour also has his meter at the same pole. And his two wires are taken from L1 and L3. And that is also consistant with a Delta configuration.

And since a Y configuration requires 4 wires, L1, L2, L3 and N, I am reasonably sure it's Delta.

I forgot to mention, I am in Isaan, so maybe they did things different here than in BKK, as the electricity system here is probably newer. I think they got electric power in this village some 15 years ago....

[Crossy]

Was out with the flashlight and had a look again. The neigbour also has his meter at the same pole. And his two wires are taken from L1 and L3. And that is also consistant with a Delta configuration.

And since a Y configuration requires 4 wires, L1, L2, L3 and N, I am reasonably sure it's Delta.

I forgot to mention, I am in Isaan, so maybe they did things different here than in BKK, as the electricity system here is probably newer. I think they got electric power in this village some 15 years ago....

From what you describe, yep it's a delta, first I've come across here. Until now I thought only Norway (Finland?) and the Philippines used this sytem for domestic, learn something new every day

So long as you're aware of this there should be no issues, it will be interesting what you see between each phase and ground, I doubt it's truly floating.

[Gimbo]

We'll see when I meassure. Getting a voltmeter tomorrow when I go to town to stock up on groceries. The place I got the wiring had a few for sale.

I trained as an electrician in Norway, but thats 20 year ago, and the company whent bankrupt before I got my certification, and I never worked as one. But I think I should be able to remmeber how to use one of those, he he

Edited December 16, 2007 by Gimbo

[Gimbo]

Been reading some other threads on electricity issues since we renovated the house and put a new system in. And some posters have reported that they where surprised to find both wires to be live. Could it be that those also where indeed also Delta configurations (assuming mine is), where both wires is actually supposed to be live, with no neutral?

Yeah I do realise that it is more likely to be faulty wiring since the Y configuration is more common...but still?

[gharknes]

Perhaps you can do a little experiment for me then, in your bare feet touch the live pin of your mains - then when you have survived that, run the water tap and do same, let us know how you get on ***flame removed**

oh and just so everybody can learn from your vast knowledge, is the AC alternating between 0 and 240v or -120 to +120, and just to add another question - is ground the same potential as the negative side of the mains, if you survived please explain

Why do these threads always degenerate into flame wars, particularly when someone (you) posts faulty or downright dangerous advice? You have not demonstrated how your grounding techniques work, rather you have resorted to insulting fellow board members.

I'm not going to get hold of the live pin of anything because I'm not stupid, although I have no doubt that I would PROBABLY survive (I've survived far worse shocks in my life, I don't really want to push my luck), this does not demonstate anything about grounding.

The 220V AC supply alternates between approximately +311V and -311V fifty times a second.

The ground is at approximately the same potential as the NEUTRAL of the supply (the mains does not have a negative side) as the neutral is connected to ground at the transformer and by the MEN / PME link in your consumer unit.

It is painfully obvious that you are lacking in basic electrical knowledge. I am not going to continue to bite on this subject, sorry.

LOL, so AC mains is 622v peak to peak, did they really teach you that........................it's all relative to ?????????

[david96]

Was out with the flashlight and had a look again. The neigbour also has his meter at the same pole. And his two wires are taken from L1 and L3. And that is also consistant with a Delta configuration.

And since a Y configuration requires 4 wires, L1, L2, L3 and N, I am reasonably sure it's Delta.

I forgot to mention, I am in Isaan, so maybe they did things different here than in BKK, as the electricity system here is probably newer. I think they got electric power in this village some 15 years ago....

From what you describe, yep it's a delta, first I've come across here. Until now I thought only Norway (Finland?) and the Philippines used this sytem for domestic, learn something new every day

So long as you're aware of this there should be no issues, it will be interesting what you see between each phase and ground, I doubt it's truly floating.

There are 3ph 3 wire 220volt delta connected systems around but not very common, they are isolated from earth, not sure if they are used in rural areas of Thailand. The 3ph 4 wire 220/380volt 50Hz system with the neutral of the network earthed is the most common.( Dy11 )

[Tywais]

LOL, so AC mains is 622v peak to peak, did they really teach you that........................it's all relative to ?????????

220VAC is the RMS value, converting from RMS to Peak = 220 x 1.414 = 311V and peak to peak is 311 x 2 = 622.

[Crossy]

LOL, so AC mains is 622v peak to peak, did they really teach you that........................it's all relative to ?????????

Er, yes, what did they teach you?

It's relative to whatever reference you're using (which can be either pole of the supply the result is the same). If you ground the neutral as is common practice in Y connected systems and use ground as the reference then it's relative to ground.

EDIT You seem to be very good at rubbishing my professional opinion, however you've failed to substantiate any of your arguments.

Edited December 17, 2007 by Crossy

[Crossy]

There are 3ph 3 wire 220volt delta connected systems around but not very common, they are isolated from earth, not sure if they are used in rural areas of Thailand. The 3ph 4 wire 220/380volt 50Hz system with the neutral of the network earthed is the most common.( Dy11 )

Yeah, that's my experience too. The only delta connected domestic supply I've actually had experience of is in the Philippines where it's 220V 60Hz phase-phase.

Evidently we have a few in Thailand too, we'll have to be careful with our advice on MEN etc.

[klikster]

LOL, so AC mains is 622v peak to peak, did they really teach you that........................it's all relative to ?????????

220VAC is the RMS value, converting from RMS to Peak = 220 x 1.414 = 311V and peak to peak is 311 x 2 = 622.

Unless I'm not understanding what you are saying, I'm having trouble with this.

How does a 2 wire AC service swing to negative? Negative compared to what? This says it better than I could .. although it's about 110 vs 220, but all else is the same .. except frequency.

"The 115 to 120 Volt household AC voltage actually swings

sinusoidally (or smoothly) from zero volts to a peak of about

165 Volts, then back to zero and continues to a peak of -165

Volts and back to zero again. It repeats this 60 times a

second here in North America."

I believe 622 V P-P would get you 440.

I may be wrong .. but that's nothing new.

Edited December 17, 2007 by klikster