Electrical Distribution/ Electrical Installations Thailand 2012.

[electau]

LV Electrical distribution system . Thailand.

The LV electrical distribution system in Thailand is 220/380V 4 wire 50Hz. Distribution is also at 220V single phase 2 wire 50Hz. Single phase transformers are supplied from 2 phases of the 3 phase HV distribution.

The neutral conductor of the LV distribution system is NOT earthed. essentially it is classed as an IT system under IEC definitions. China (PRC) also uses this system and do a number of other countries in the region.

Distribution conductors are insulated.

Metering. The standard meters are 5/15A and 15/45A single phase 220 volt. meters are of weatherproof construction.

An Electrical Installation commences for all practical purposes at the load side of the PEA/MEA metering point. It is not part of the distribution system.

The minimum size of consumers mains from this point to the main switchboard or load centre is 10sqmm or 16sqmm copper.

The minimum size of main switch MCB is 60/63A 2 pole 10kA at 220V.

The Square D suface mounted sheet metal load centre is basically the minimum standard for a distribution board.

This standard is suitable for most stand alone houses, town houses, shophouses, and multi tenanted buildings.

Multi tenanted buildings are generally supplied from an individual transformer and are bulk metered, the buiding management is responsible for sub metering of individual units.

Socket outlets. 2 pin socket outlets are standard. 3 pin socket outlets are available. the 2 flat blade and the 2 pin round pin plug tops are standard.

The 3 pin NEMA type plug top is available along with the TIS 3 round pin plug top. The TIS plug top will eventually replace the NEMA one.

Earthing/Grounding.

There is no main earth of main earth electrode.

Earthing of electrical equipment/appliances is in accordance with the manufacturers instructions. This earthing is direct and is to minimise the effects of any leakage current.

Earth leakage/ ESB/ELCB/ RCD/RCBO. May be installed for additional protection.

Advice on electrical equipment and installation requirements may be obtained from the following sources.

Homepro, Electrical section.

Square D company (Thailand)

Safe-T- Cut (Thailand)

Schneider Electrical (Thailand)

Electrical Contractors are listed in the Thai Yellow Pages.

Information current 30/01/2012.

　

　

　

　

　

　

Edited February 6, 2012 by electau

[Crossy]

Interesting Electau.

Do you have a link to the source of this information?

Specifically the assertion that it's IT as all the documents I have show a MEN system with a grounded neutral. Neutral may not actually be grounded at the Tx, but it's certainly grounded by the MEN links and local ground stakes.

[electau]

One obtained this information by visual checks on several Thai electrical installations. Also visual checks on a number of transformers.

Most had Square D loadcentres. I found no evidence of main earth or electrode. None had RCDs fitted.

Homepro, Electrical section had 3 wiring diagrams displayed.

1 Loadcentre with 2 pole MCB and ! pole MCBs for sub circuits. Neutral not earthed.

2 Loadcentre with 2 pole MCB plus one SAFE-T-CUT ELCB.

3.Loadcentre with 2 pole MCB plus one 63A/ 30mA IEC RCD.

Both drawings 2 and 3 showed the incoming neutral earthed but the drawing did not indicate an earth electrode, just the international earthing symbol.

(It would appear that earthing of the neutral is only required if RCDs are installed).

　

[electau]

Here is one example, a nine floor condo block supplied by a 500kVa transformer, multiunited, no RCDs, no earthing, built within the last 2 years

[Crossy]

Here is one example, a nine floor condo block supplied by a 500kVa transformer, multiunited, no RCDs, no earthing, built within the last 2 years

Compare and contrast with our condo block. 18 floors, 165 units, on a 1100 kVA Tx.

Built approximately 18 years ago, the ubiquitous Square-D CU, no RCDs (but no surprises there considering the age), all outlets are 3 pole and actually have the ground connected back to the CU.

Supply appears to be MEN (or at least TNC-S), there's a low impedance path between the ground bar and neutral (low enough that the aircons were originally powered by the ground bar). Neutral appears to be grounded, at least there is a fairly low impedance between the neutral and the balcony railing, we're on the 10th floor so I've not been able to verify against an independent ground.

Lighting circuits are unsurprisingly not grounded, but at least all are switched in the live.

Outlets are wired in 4mm singles on 16A breakers, lighting is in 2.5mm on 16A breakers, the shower is also in 4mm and on a 32A breaker. Colours are Thai standard Black, White, Green.

With the addition of RCBOs on critical circuits on the whole a reasonably safe installation. I've been in several units so it's not just ours that's wired like this, I strongly suspect that this is the original 18 year old installation.

Great info on the observation front electau, we do however have to be a bit careful with information we provide here, particularly differentiating between what is supposed to be installed (MEN, RCDs, 3 pin outlets), with what is often installed (none of the above).

[Crossy]

This is the wiring diagram from one of the government provided plans, very basic but it does show:-

1. An RCD.
   
2. A 3/8" by 2.4m ground rod (indicated by the ground symbol).
   
3. MEN (N-E connection), although I don't particularly like the way that this is implemented.
   
4. Outlets wired in 2.5/1.5 VAF-GRD implying that they are 3 pin and grounded.
   

Since this came from a government source I suggest that this is the nearest we are going to get to an 'official' regulation and should be considered as the minimum requirement for a new build.

Thoughts?

[electau]

Thanks for the info Crossy.

What I documented was electrical installations "as built".

They consisted of :

1. A simple installation of 2 or 3 two pin socket outlets protected by a single MCB.

2. A typical shophouse installation.

3. At least 4 standalone houses.

4. 2 townhouses.

5. A 9 floor condo unit less that 2 years old.

Numerous visual checks of many load centres.

Most electrical appliances have 2 pin plug tops and twin PVC sheated lead. The earthing requirements are in the instruction manuals.

On a Samsung microwave the instructions from the manufacturer "To prevent electric leakage please connect the ground wire to the ground" A Samsung refrigerator has a diagram of how to earth the appliance in the instuction manual. The same with a DVD player this has a grounding terminal on the rear of the panel.

On a HW unit, marketing infomation, "ESB/ELCB and earthing terminal for your additional protection"

　

Diagrams 1,2,3.

Those drawings appear to originate from one of the circuit breaker/load centre suppliers.

Square D and the other suppliers should be able to give the requirements for earthing, and that means one should contact them. Other sources are reputable electrical contractors.

IMO.(only)

There are two options. refer to diagrams 1, 2 and 3.

1. Maintain the status quo and do not earth the neutral.

2. Install RCDs and earth the neutral ( It may not be practicable to earth to an electrode) the earth is to ensure operation of RCDs.

If a MEN system is used, ALL electrical installations on the same transformer must be MEN.

and only if there is a proven testing and regulatory system in place. With the MEN system all exposed conductive surfaces must be earthed, eg, aircons, hws, hotplates, earth terminal of 3 pin sockets. 2 pin sockets must not be used. ( separate stand alone houses on separate titles).

Option 2 in practice operates as a TT system.

There is no reason why a TN-S system ( separate L,N,E conductors) from a common transformer supplying a multi tenanted building) can not be used. Each Loadcentre will have an incoming L, N,and E. This appears already in use for some types of electrical installations.

Option 1 and 2 would be suitable for townhouses and shophouses also individual houses and most electrical installations.

　

　

　

[electau]

That drawing of a Thai MEN system as implimented is one very good reason NOT to use it.

1. PE conductors should terminate on a separate earth bar.

2 Unprotected neutrals to the main neutral bar.

3. RCBO neutrals to a neutral bar on the load side of the RCBO.

4. Main earth conductor must be run from the earth bar.

5 The MEN link must be between the main neutral bar and the earth bar.

For test purposes just disconnect the MEN link. Testing can not be done correctly as per the existing drawing.

[electau]

SAFE-T-CUT (Thailand)

http://www.safe-t-cu...?name=knowledge

This has some info along with an earthing system. No reference to earthing of the neutral.

Product info also.

Edited February 8, 2012 by electau

[electau]

Safe-T- Cut does give reference to earthing the neutral, when RCDs are installed. There appears there is no connection between the earthing system and the main neutral.

[Crossy]

That drawing of a Thai MEN system as implimented is one very good reason NOT to use it.

1. PE conductors should terminate on a separate earth bar.

2 Unprotected neutrals to the main neutral bar.

3. RCBO neutrals to a neutral bar on the load side of the RCBO.

4. Main earth conductor must be run from the earth bar.

5 The MEN link must be between the main neutral bar and the earth bar.

For test purposes just disconnect the MEN link. Testing can not be done correctly as per the existing drawing.

Yup ^^^. We will not be doing it that way (I did say I didn't like it), the PEA Grounding booklet shows the same dodgy arrangement so it seems to be a Thai standard.

Removable N-E link on the load side of the main incoming breaker (before any RCDs) so we can be totally isolated from the incoming supply. If Sparky doesn't agree I'll get him to TT the whole lot and add the link when he's gone

[electau]

I think we have a difference of option here, there are always alternative methods which will obtain the same result.

This is why one would use the AS3000 earthing requirements. If you wish to use the TT system on new installations the link is not connected.

The cost and fitting of an earth bar to the load centre is no great problem.

RCBOs have been available in Thailand for at least for the last 25 years (Safe-T-Cut brand).

I have seen them fitted but with no neutral earthing. Again a HWS with a 10mA RCD fitted internally to the unit, no mention of neutral earthing.

So there appears to be options available. Basically if the electrical specifications state to earth the neutral and if there is no formal specifications you have an option.

It will be interesting what tests are carried out prior to initial connection and testing of the RCDs, L to E at a socket outlet not just the test button when power is connected.

You should test the RCDs as a TT installation and then with the N to E link. You might find it preferable to maintain the TT connection.

And there will always be the 2 pin socket outlet and 2 pin plug top along with the 2x 1.5sqmm extention lead and 2/3 pin power boards.

[electau]

The earthing of the neutral as implimented in Thailand may have originated in the USA (NEMA). This would explain why load centres are not fitted with an earth bar.

It would be interesting to see how neutral earthing (grounding) is carried out in the US on electrical installations.

[T_Dog]

When the power company ran the last 300 meters to our project, they first had an engineering drawing drawn up and we had to await for it to get approved higher up. The drawing and installation have a lightning arrestor on the last pole, and a wire is run down the pole to an earth rod. The neutral line is connected to earth at that point.

Edit... Just saw the new post. The load center (distribution panel) we are using has separate neutral and ground bars. The ground bar is run to earth. No connection between neutral and earth at the load center.

Edited February 15, 2012 by T_Dog

[electau]

Actually T_Dog one was refering to the neutral earthing at the main switchboard or load centre of an electrical installation. Also if the earthing conductors are connected to a seperate earthbar or to the main neutral bar.

Thailand follows many requirements that have originated from the NEC, terminology, wire colours, and two types of load centre are available, the Euro DIN and the US plug in type.

[T_Dog]

Thanks..... I got it now.

[electau]

Under the US NEC code the main neutral link may be used as a termination point for the PEs( grounding conductors).

This is why that this method of implimentation is used in Thailand.

[electau]

The PEA issued a document available on their website in English re " Instructions on the use of Electricity" on the 10th June 2009. Part of this is reproduced here ( the English has been made readable). It can be downloaded from the PEA website.

The PEA requests customers comply with the instructions on the use of electricity.

In designing and installing electrical appliances/equipment they must be in accordance with the Thai Electrical Code.

A grounding system and residual current device(s) must be installed.

Note on the above.

The grounding system as implimented complies with the US National Electrical Code (NEC).

It would appear that the Thai Electrical Code is based on the US National Electrical Code.

With the NEC method of implimentation a common neutral /earth bar is used. The neutral is earthed (grounded) to an electrode and the individual circuit neutrals and protective earth conductors are connected to the common neutral/earth bar.

Edited February 19, 2012 by electau

[Crossy]

It can be downloaded from the PEA website.

It's here http://www.pea.co.th/pdf/SafetyUseE.pdf

[Artisi]

Please clarify some confusion on my part, my house wiring system has just been completed. I'm afraid I don't really trust the sparkie to have done the right thing thru-out the complete system so have started a check of my own - first thing I noticed and which is contrary to good practice and completely against what I instructed was " no twisted and taped wire connections" looked at 2 power outlets that I knew would have problems if there was to be a problem - and yes - twisted and taped connection - this is also a problem on some of the light fiitings.

Of course this is enough for me to say to the builder "not acceptable - the wiring is not as I wanted nore is it correct - get it fixed" - final payment is now being negotiated.

Secondly, RCBO's and the confusion,using my multimeter - from L to N I read full voltage - from L to E I also read full voltage and the RCBO doesn't trip - I expect the RCBO to trip as I assume the L to E is what we are supposed to be monitoring. I haven't established as yet if the N and E are connected, the earths are supposedly all connected outside of the switchboard somewhere so can't easily check this out or see if E and N is connected anywhere.

Any comments welcomed on the RCBO (my confusion)

Edited February 21, 2012 by Artisi

[bankruatsteve]

Please clarify some confusion on my part, my house wiring system has just been completed. I'm afraid I don't really trust the sparkie to have done the right thing thru-out the complete system so have started a check of my own - first thing I noticed and which is contrary to good practice and completely against what I instructed was " no twisted and taped wire connections" looked at 2 power outlets that I knew would have problems if there was to be a problem - and yes - twisted and taped connection - this is also a problem on some of the light fiitings.

Of course this is enough for me to say to the builder "not acceptable - the wiring is not as I wanted nore is it correct - get it fixed" - final payment is now being negotiated.

Secondly, RCBO's and the confusion,using my multimeter - from L to N I read full voltage - from L to E I also read full voltage and the RCBO doesn't trip - I expect the RCBO to trip as I assume the L to E is what we are supposed to be monitoring. I haven't established as yet if the N and E are connected, the earths are supposedly all connected outside of the switchboard somewhere so can't easily check this out or see if E and N is connected anywhere.

Any comments welcomed on the RCBO (my confusion)

Volt meters are high impedance and won't trip a RCD.

[Crossy]

Correct Steve, a voltmeter will draw a tiny fraction of the current required to trip any form of RCD.

The RCBO monitors the CURRENT in the Live and Neutral wires, when there is a DIFFERENCE in these currents of 30mA (or 10mA or 100mA depending upon the device rating) then the device assumes this current is going somewhere it's not wanted (through you) and disconnects the supply.

An RCBO also provides protection against overload (like an MCB), an RCD only provides earth leakage protection, there is no overload trip.

Both an RCD and RCBO will function properly provide shock protection WITHOUT an earth. An earthed system improves safety by making it more likely that, in the event of a fault, any leakage will pass directly to earth rather than via a human.

[regedit]

Are the SafeTcut devices RCDs or RCBOs ? I guess RCDs. Would a consumer unit protected by a SafeTcut device be expected to have nuisance tripping so would be better to fit a split-load unit ?

[Crossy]

The big boxes of air that are marketed by Safe-T-Cut are RCBOs.

They also make RCDs and MCBs just to cause confusion.

Nuisance trips are somewhat preferable to death by electrocution, however a split-load CU will give you the best of both worlds if correctly configured.

[Artisi]

Thanks for the info on the volt meter, I didn't even consider the low current draw across the multimeter - the RCBO's are seperate units on each of the power circuits.

Would a 15 watt test lamp work ok to test L to E to ensure the RCBO's function.

[Crossy]

Thanks for the info on the volt meter, I didn't even consider the low current draw across the multimeter - the RCBO's are seperate units on each of the power circuits.

Would a 15 watt test lamp work ok to test L to E to ensure the RCBO's function.

That is one of the DIY tests, yes.

Not perfect, but better than nothing.

[Artisi]

Thanks for the info on the volt meter, I didn't even consider the low current draw across the multimeter - the RCBO's are seperate units on each of the power circuits.

Would a 15 watt test lamp work ok to test L to E to ensure the RCBO's function.

That is one of the DIY tests, yes.

Not perfect, but better than nothing.

Ok, thanks for the info. I'll sleep a bit easier knowing that they (RCBO's) function and not just there for decoration.

[electau]

Yes, a 15W 220/240V test lamp connected between L and E at a socket outlet will trip a 30mA RCD.

Edited February 21, 2012 by electau

[electau]

The main neutral is earthed to an electrode at the main switch board (MSB). If there is more than one distribution board (DB) in an electrical installation such as in a multi tenanted building (eg a condo) a separate earthing conductor must be run from the main switchboard earth bar to each distribution board. The DBs earthing must not be bonded to the neutral.

In practice in Thailand the earth conductors at the distribution board MAY be found bonded to the sub main neutral. It is possible that this MAY be permitted in Thailand if the distribution though the building are reticulated or rising sub-main(s) from the main switchboard. In other words the submain neutral becomes a PEN conductor, the same as the main neutral.

Nothing in the PEA document on that subject.

If you live in a condo you should have a L. N. and E into the distribution board (ie consumer unit).

Note. the SAFE-T-CUT adjustable sensitivity RCBOs have a 5mA setting. This 5mA is mentioned in the NEC for their GFCIs (RCDs).

[bankruatsteve]

The main neutral is earthed to an electrode at the main switch board (MSB). If there is more than one distribution board (DB) in an electrical installation such as in a multi tenanted building (eg a condo) a separate earthing conductor must be run from the main switchboard earth bar to each distribution board. The DBs earthing must not be bonded to the neutral.

In practice in Thailand the earth conductors at the distribution board MAY be found bonded to the sub main neutral. It is possible that this MAY be permitted in Thailand if the distribution though the building are reticulated or rising sub-main(s) from the main switchboard. In other words the submain neutral becomes a PEN conductor, the same as the main neutral.

Nothing in the PEA document on that subject.

If you live in a condo you should have a L. N. and E into the distribution board (ie consumer unit).

Note. the SAFE-T-CUT adjustable sensitivity RCBOs have a 5mA setting. This 5mA is mentioned in the NEC for their GFCIs (RCDs).

It might be noteworthy to mention that GFCI's are usually at the receptacle (is the receptacle). ie: RCD circuit protection is not common in the states.

And, no issues here, but it's not clear to me where you are going with this thread? Like, are you doing research for a defacto Thai code, or?? Just curious.