Thailand transformer opinions please.

[La Poste]

Ok here's a few pictures of my mates transformer that supplies his property, his property is in northern Thailand.




I know the pictures are not great but the tranny doesn't look like it has an earth.
If it has no earth what would members suggest doing to make it safer?
I was thinking:

1. Rod the neutral at the property end to keep the neutral at a safe voltage.
2. Wire the place as normal and then put in a separate earth rod at a certain distance from the neutral rod.
3. RCD or RCBO everything.

I was thinking of installing two rods, one for the neutral and one for the earth so that in the event of say a lost neutral (I'm not a scare monger) the voltage on the metalwork would not jump up, I think a lost neutral in this part of the world is a probable occurrence what with storms and overhead lines.

Does this sound good to people, does this sound like a sensible approach?
Are there any inherent dangers in this approach?
Am I on the right track?

Comments appreciated.

Thanks.

 

[La Poste]

I was sort of thinking along the lines of PNB.

From what I have read PNB is where a property is supplied by a single transformer and the transformer star point is not earthed at the transformer but at a remote place where the earth and neutral are separated.

This overhead transformer supplies my mates farm but I am not sure yet of how many other properties.

With PNB you can also build a TT system and have the TT rod at a separate place from the neutral/rod bond.

The fact the Neutral rod and earth rod are fairly local to each other means you would get a nice low resistance reading between the two rods hence make your earth fault protection more reliable.

My mate says he will send more pictures of the transformer in time but he is not in Thailand at the moment so I might have to wait.

I just wondered what people thought of unearthed transformers and how to make them safer as everything I come across in the UK is earthed properly and has an earthed neutral.

 

[Knobhead]

Without knowing if the neutral is earthed at the pole it's hard to say.

Definitely rod the house earthing, but as to the neutral ? ? ? ?

Weird way to bring out the LV tapping, looks like two studs for L and two for N. They are linked in pairs.

 

[Knobhead]

To be honest when I saw Thailand in the thread title I was expecting something wired like this.
View attachment 15050

 

[snowhead]

What's the normal practice for earthing in Thailand, apart from anything goes?

Quick search finds;

Earth rods are available at trade outlets so must be the norm.

http://www.siam-info.de/english/electrical.html

 

[StuSpiers]

TT is the norm in the sticks in thailand.

Put a Spike in - you can get really decent spikes in thailand.

Do not mess with the neutral.

Connect only earth to your spike.

You are not going to get any danger from a lost neutral with a TT system.

 

[Spazz]

Dont worry about earthing the neutral - tell him to install a RCD, that way if the neutral is dropped the RCD will pick it up and isolate the supply.

By all means rod the earth

 

[La Poste]

If the neutral is dropped how will the RCD pick it up?

The RCD will measure an imbalance between line and neutral so if the neutral is dropped there will be no current flowing through the line conductor because there will be no return path for that current to flow so all that will happen is nothing will work, the RCD will not trip unless there is an earth fault in which case the RCD would have tripped already.

I wonder why they don't earth transformers in Thailand, I mean it's not hard to put a piece of wire from the star point down into the ground, maybe they worry that people will steal it.

The reason I talked about earthing the neutral was because there was a thread on this site a while back about a guy living in Romania I think (I will try to dig the thread up) and the advice given to him by both Marvo and Engineer 54 was to earth rod the neutral at the point of entry of the property, then after rodding the neutral wire the house as normal and connect the earth to the neutral at the point of entry sort of like a TNC-S.

Using the information in this thread I thought it might be a good idea to rod the neutral in this instance thus ensuring the neutral stays closer to earth potential and provides less of a potential danger but reading comments posted in this thread it seems a bit of a no no, could someone explain why it is a no no to rod the neutral.

Thanks.

Here's the thread:
http://www.electriciansforums.net/non-uk-electrical-works/52901-unusual-foreign-electrics.html

 

[La Poste]

Any takers?

It's something I'm really interested in.

 

[ayjay]

hi, i travel to thailand(phuket/patong,) twice a year for a 1 month stay at a time
they rarely earth anything, even some appliances arn,t earthed that should be
the plug will fit into the socket either way round as well,
the meters are sometimes fixed to a post outside in the rain with no cover on the terminals
electrocution is commonplace, but is put down to an "accident"
the recent fire that killed 6 at the tiger complex(bangla road) was put down to an exploding transformer during a monsoon rainstorm)
they just use rcd,s on everything, but some are ajustable( 30ma-to 100ma)

 

[Knobhead]

If the transformer was supplying just the one property I’d have no qualms about rodding the neutral. But other properties are an unknown quantity, what faults do they have that could rear their ugly heads.
Another little conundrum is “which is the neutral?” I know what I’d do and that’s test to find which has the least faults.
Are you going to be doing the work? I wouldn’t fancy trying to do it remote via e-mail.

 

[La Poste]

I don't think I'll be doing the work, the guy is in the UK right now and won't be back there for about a year.

I was just curious to know why it was acceptable to rod the neutral in one previous thread but not in this particular instance.

Tony when you say you would test for the one with the least faults what do you mean, could you elaborate a little more and don't worry I'm not going to go rushing out with my test equipment and try it I'm just curious how you would test which one is the neutral and what sort of faults you are talking about.

Thanks.

 

[Engineer54]

I can't see how the neutral can't be earthed at the TX, otherwise the neutral point will be all over the place unreferenced!!

I can't blow up the photo's so i can't see too much, but on a lot of these cast concrete poles they use the reinforcing steel bars as the down conductor which are then connected to a rod at it's base.... As i say i can't make out at the moment, exactly what or how the LV connections come out of this TX.... lol!!

 

[Knobhead]

Ahha, that would explain the bolt arangement below the transformer.

 

[sparks1973]

To be honest when I saw Thailand in the thread title I was expecting something wired like this.
View attachment 15050

lol...they`l be throwing `hookups` over next as a `tap off`..lol...

 

[ayjay]

saw this last year

 

[Knobhead]

Oi!, I can remember where every wire goes!

 

[Knobhead]

Neutral to the top, some UK electricity boards used to do that for coastal installs.

 

[ayjay]

its a bit of a mess tony!
the new buildings have much better wiring supplys but the general ovehead suppys are terrible
there are power cuts when it rains heavily, in the rainy season thats most days
i would have liked to photograph other dangerous stuff but didn,t, as the owners of various premises might not have liked me doing that!
these2 reports are the top of the iceberg, i know of one man that was elecrocuted when he touched the fridge
and a little aussie boy when he plugged in his computer game after he left the pool and was wet
Phuket NEWS: Phuket tourist electrocution sparks probe, safety bli

Briton's electrocution in Phuket was an accident, says court ruling

 

[Knobhead]

I can't see how the neutral can't be earthed at the TX, otherwise the neutral point will be all over the place unreferenced!!

The voltage is referenced to it’s self. In testing we always used either – or L2 for our earth free systems, it’s not referenced to earth it just a convenient way for us to record readings. We had both AC and DC systems.
Earth faults are a major headache, you don’t know they are there until you’ve got two of them on opposite lines. Durham mentioned the way ship bourn systems worked a while ago, I think it was similar to what we used.
View attachment 15139

If you want earth leakage detection then it gets complicated, the system we used for the 660V AC system used DC injection through chokes. It was a pain in the backside, it would trip at 20mA on a 2.6MW system.

 

[Darkwood]

I started reading the OP and saw the words 'tranny' and 'Thailand' .... for a minute i thought i was on the wrong forum....:bow:.

 

[Knobhead]

There isn't a button for throw bucket of cold water!

 

[La Poste]

Great stuff thanks for the replies.

So if I was not sure whether a TX was earthed how would I test this?

Would it be a good idea to bang a nice long rod in and then do a live loop test between supply line and the rod, if I got no reading or infinite resistance would that show the TX was not earthed?

What about taking a voltage measurement between the neutral conductor (assuming it's marked) and true earth?

Is there a method of testing to see whether a TX is earthed or not?

 

[Knobhead]

That would be quick and easy.

 

[La Poste]

That would be quick and easy.

Sorry Tony I don't understand what you mean by quick and easy.
Are you saying my method is quick and easy?

 

[Knobhead]

Yes, may take you a while to get there though.

 

[Engineer54]

The voltage is referenced to it’s self. In testing we always used either – or L2 for our earth free systems, it’s not referenced to earth it just a convenient way for us to record readings. We had both AC and DC systems.
Earth faults are a major headache, you don’t know they are there until you’ve got two of them on opposite lines. Durham mentioned the way ship bourn systems worked a while ago, I think it was similar to what we used.
View attachment 15139

If you want earth leakage detection then it gets complicated, the system we used for the 660V AC system used DC injection through chokes. It was a pain in the backside, it would trip at 20mA on a 2.6MW system.

Not sure how that would work on a distribution system covering several consumers, with different loads on different phases... And as you say RCD's (which they use in abundance) wouldn't functioning to well.

 

[Knobhead]

Not sure how that would work on a distribution system covering several consumers, with different loads on different phases... And as you say RCD's (which they use in abundance) wouldn't functioning to well.

The very thought of it gives me a headache.

Will PM a drawing of what we used for 660V

 

[La Poste]

Here's a few more cropped images of the TX, it does look like at least one cable has been anchored to the pole by means of a bolt.

Maybe this is evidence of the steel within the pole being used as an earth.

I like the tap at the bottom of the TX, I've never seen one of those before.

 

[Knobhead]

Looks like that's the mystery solved. I'll admit, I'd never have thought of using the poles reenforcing as an Ufer earth.

PS the tap, all oil filled transformers have them. Usualy with a bung fitted. They are especialy designed for numb-nuts elecricians mates to leave part open, as i found out in the middle of the night when half the works shut down. 20MVA transformers don't like running low on oil.

 

[Engineer54]

Looks like that's the mystery solved. I'll admit, I'd never have thought of using the poles reenforcing as an Ufer earth.

PS the tap, all oil filled transformers have them. Usualy with a bung fitted. They are especialy designed for numb-nuts elecricians mates to leave part open, as i found out in the middle of the night when half the works shut down. 20MVA transformers don't like running low on oil.

Usually used just as the down conductor, then a rod or whatever taken off that down conductor. In this case that may be a galvanised plate that runs down to ground level shown in the photo's, so the rod would be taken of of that plate probably underground where it can't be readily seen... Can't really see too clearly, if that is a plate sitting in a recess on the pole, in some photo's it does indeed look as if it is...