Earthing & Distribution Systems In Thailand.

[elkangorito]

The current situation is that 3 main types of systems are evidently in use in Thailand, with the possibility of another system (delta).

Those are:

a] TN+(C+S).

b] TT.

c] IT.

Personally, I have only seen the a] & c] in use in Thailand. I have never seen a TT system here.

Some time ago, longball53098 posted some info regarding the PEA. His post is via the link below.

http://www.thaivisa.com/forum/Thai-Domesti...t&p=2397709

Longball, could you please provide more info about the booklets i.e. are the booklets still available? Would it be too much trouble to scan a copy (42 pages) & post it here?

The below 2 images come from Longball's post & clearly show an MEN link. The problem is, this can only be done if the supply transformer (tx) neutral is solidly earthed via a minimum 6m long earth stake (that's right...6m long/deep).

Showing the booklet to a Thai electrician may cause a problem if the tx neutral is NOT earthed & the sparky is not familiar with a TN system.

Also & if a TN system is used, it is imperative that Earth Fault Loop testing be carried out & cable lengths are such as to allow any circuit breaker to trip in the required time. If these things are not done, one may as well use a TT or IT system (no MEN) & ensure that all circuits are protected by RCD's.

[longball53098]

Some time ago, longball53098 posted some info regarding the PEA. His post is via the link below.

I will make a stop to the local PEA office and see if they have some books and grab a couple. If you like I could post it to you rather than scan it.

[david96]

In Thailand one has only seen the IT system utilised and some areas may be TT on installations, and they have to be visually verified.

Transformer earthing an electrode 6 meters? I think that can be interpreted as a trench with multiple earth electrodes bonded together. Equal to or better than.

The minimum earthing resistance is generally regarded on LV distribution network at the tranformer as 10 ohms. (Visual check to see if earthing has been implemented).

Drawing 1 appears to show a MEN link. Drawing 2 shows a MEN link but only a 2 pin socket outlet, no PE. Protection is by RCD only. Main earth electrode indicates 2.4M in the ground.

Earth fault loop impedance or verification of impedance. AS3000.2007 Clause 8.3.9 ( as a guide)

Where an installation includes circuits containing socket outlets not protected by an RCD the impedance required for automatic disconnection of supply shall be verified on each such circuit by:

1. Verification of the total resistance of the active and protective conductors ( using a continuity tester); or

2. Where supply is available verification of the earth fault loop impedance. (With a suitable instrument designed to measure low values of impedance).

If you install RCDs loop impedance testing is not required.

[longball53098]

Some time ago, longball53098 posted some info regarding the PEA. His post is via the link below.

I will make a stop to the local PEA office and see if they have some books and grab a couple. If you like I could post it to you rather than scan it.

I went out for lunch and made a stop at the Banchang PEA office and grabbed 2 of the booklets. Came back this afternoon and scanned the booklet cover to cover and saved as a PDF. Its too big to post here as it's over 25Mb but if someone wants it I can email to you.

[Crossy]

I went out for lunch and made a stop at the Banchang PEA office and grabbed 2 of the booklets. Came back this afternoon and scanned the booklet cover to cover and saved as a PDF. Its too big to post here as it's over 25Mb but if someone wants it I can email to you.

Cheers for that, at 25megs it's too big for my email.

Upload to Rapidshare http://rapidshare.com/ with a small file I don't think you need premium membership (PM me if you have problems, I have a premium account).

Share the link here

QED

[Daffy D]

I'm not a qualified electrician but have done lots of wiring and various "do it yourself"electrical jobs over the years and have managed to live to old age without killing myself but the more I read about Thai systems the more confused I get.

I notice in the diagram of the house wiring in the OP the earth is connected to the neutral.

I always thought that the Earth wire should be a separate connection, Is there something different about Thai wiring that favors this arrangement ?

In my consumer unit I have one bar connection for all the neutral wires and one bar that is connected to the metal box for earth connections, this seems normal to me.

Should I make a connection between the neutral and the earth?

[InterestedObserver]

Should I make a connection between the neutral and the earth?

And that, kind sir, is the real question.

[longball53098]

I went out for lunch and made a stop at the Banchang PEA office and grabbed 2 of the booklets. Came back this afternoon and scanned the booklet cover to cover and saved as a PDF. Its too big to post here as it's over 25Mb but if someone wants it I can email to you.

Cheers for that, at 25megs it's too big for my email.

Upload to Rapidshare http://rapidshare.com/ with a small file I don't think you need premium membership (PM me if you have problems, I have a premium account).

Share the link here

QED

Crossy you made me get my brain in gear and it dawned on me (the big light came on) and I thought why is this file so big? And how do I make it manageable? Dah!

When I scanned the booklet and saved it in a jpg format all I had to do was resize the file like any other jpg and wah lah I have a smaller 1.9MB pdf now. So here it is if I did all this correctly.

PEA_Doc2.pdf

[elkangorito]

Should I make a connection between the neutral and the earth?

No. This cannot be done unless your 'arrangement' has been physically verified as being suitable by a qualified person.

When I scanned the booklet and saved it in a jpg format all I had to do was resize the file like any other jpg and wah lah I have a smaller 1.9MB pdf now. So here it is if I did all this correctly.

Great work Longball

I'll see if I can get it translated...this may take some time. I know a couple of electrical teachers that speak English reasonably well.

Nonetheless, the booklet does seem to promote the use of a TN type system. The strange thing is that the transformer at a new establishment near me (a condo block not 6 months old) is installed as IT. I live in a PEA area.

[Crossy]

Those who are confused by our references to TT, TN-C-S etc etc, may find this document useful

24128363_2005_16_Autumn_Wiring_Matters_Earthing_Your_Questions_Answered.pdf

Note that being a UK document it uses the European wiring colours, brown - live (phase or active), blue - neutral, green & yellow - earth (ground).

It is worth stressing (again), that unless you KNOW what earthing system has been installed it is safest to assume TT (or IT) and use an independent ground stake with 30mA RCD (RCCB, ELCB, Safe-T-cut).

Great stuff Longball, that leaflet should be required reading for all Thai sparks (with Elks rider in post #1).

[elkangorito]

Good doc Crossy

[david96]

Australian Standards, AS/NZ3000/2007 Permanent fixed wiring, Colour codes.

Red. phase or active conductor.

White. phase or active conductor.

Blue. phase or active conductor.

Black. neutral conductor.

Green/yellow trace. earthing conductor.

Brown and Grey. control wiring.

Any colour with a black trace. control wiring.

Any colour with a colour trace. control wiring.

Flexibles, Single phase. Brown. Active. Light Blue. Neutral. G/Y earth.

Multi phase Red. phase

White. phase

Dark blue. phase

Black. neutral

Green. earth.

European, Flexibles.

Brown. phase

Black. phase

Grey. phase

Light blue. neutral

G/Y. earth.

[david96]

It is normal practice with an MEN system to connect the incoming neutral directly to the neutral link. The incoming neutral must not be switched. All sub circuit neutrals teminate at the neutral link. The Main earth is connected directly to the earth bar and all protective earths are connected to this earth bar.

The MEN link is connected between the neutral link and the earth bar. It is removed only for testing purposes.

Source: AS/NZ3000.

[david96]

Here are some points for discussion regarding Earthing.

1. Why is earthing carried out ?

2. The function of the PE conductor.

3. The function of the main earth and main earth electrode in an MEN system

4. The function of the main earth and main earth electrode in a TT or IT system.

5. Why must the main earth connection never be disconnected while supply is connected to an electrical installation?

6.When and why must auto disconnection of a protective device occur in the event of an earth fault?

7.Touch voltage and its effects.

8.Equipotential bonding.

[david96]

While some may find Thai electrical installations confusing, with 2 pin and 3 pin socket outlets, 3 types of plug top, Euro and the American pattern, no earthing etc.

Australia never had the problems of 2 pin socket outlets unlike The UK, Europe and the Americas. We specified 3 pin socket outlets and 3 pin plug tops from the very beginning. And our socket outlets were standardised and foreign outlets were prohibited. This meant that every earth connection of a socket outlet was earthed and there would be a neutral link and main earth at every main switchboard and a neutral link at every sub board in an electrical installation. Supply Authorities installed rewirable service fuses on the phase conductors on all consumers mains. The main earth was generally the mains water supply pipe or a 3/4inch galvanised pipe electrode. We also adopted the MEN system from the beginning, although some small supply authorities used Direct Earthing and Voltage operated ELCBs, these had mostly been changed over to MEN by the end of the 1950s.

Australia had the safest electrical installations in the world and was ahead of most countries in the 1960s including the UK.

Thailand suffered because they compromised between America, Japan and European standards and different installation methods.Thailand is trying to do now that what should have been done in the first place and it will be very difficult if not impossible.

[elkangorito]

With help from a Thai colleague, I have done a brief summary of the PEA booklet. I will do a better (more complete) job after Monday.

Page 13 (picture).

Only one (1) MEN link per installation permitted.

Page 15, Table 2.

Size of earth rod in mm squared--------------------Minimum Main Earth sizes in mm squared.

<= 35---------------------------------------------------------------------------------10

35 to 50-----------------------------------------------------------------------------16

50 to 95-----------------------------------------------------------------------------25

95 to 185--------------------------------------------------------------------------35

185 to 300-----------------------------------------------------------------------50

300 to 500-----------------------------------------------------------------------70

> 500---------------------------------------------------------------------------------95

The Main Earth cable is recommended to be installed in conduit (metal or plastic).

Page 18.

It says something about Main Earth sizes if the installation is greater than or less than 100m from the distribution transformer. It refers to another document (Standard?) for the correct sizes. I think the above figures are for installations less than 100m from the transformer.

Page 20. Part 6 (Earth Stakes).

'Copper coated' rods are permitted. Metal rod inside of copper tube (copper cladded steel) is NOT permitted. (I will verify this...it sounds a bit strange.)

Can use another type if approved (e.g. hot dipped galvanised).

Minimum size - 16mm (5/8") dia & 2.4m long.

Page 21.

Main Earth connection to electrode is to be done by either welding (not soldering) or clamp.

Only one (1) Main Earth cable is permitted to be connected to an electrode.

Soil resistivity should ideally be less than 5 Ohms. In 'difficult' areas, a maximum of 25 Ohms is permitted. If over 25 Ohms, more rods are required.

Page 28.

Recommended areas where RCD's can be used - bathroom, kitchen & external.

Page 34 (applies to pics 19 to 23 only).

2. Neutral bar must be insulated from the switchboard.

3. No MEN link at sub-boards permitted.

5. Every OCPD to be a minimum 10kA.

Page 39 (summary).

1. You should have only one (1) MEN link.

2. The MEN link must be in the main switchboard.

3. All cables are to be 2c+e.

4. All outlets are to be 3 pin.

5. No earth (ground) potentials permitted.

6. Soil resistivity must be according to the 'Standard'.

7. n/a.

8. CB's are to conform to IEC 60898 & be minimum 10kA.

9. n/a.

10. To be built to 'Standard', which is dated 2545.

Throughout the whole booklet, a TN system is indicated. The distribution transformer is not mentioned (as expected).

[david96]

It would appear that the earthing arrangements costs are being born by the consumer not by the PEA/MEA in their implementation of the MEN system. These figures of soil resistivity (contact resistance) of 5 ohms and 25 ohms is what might be expected when earthing the neutral of the distribution network. It is not stated if the neutral of the distribution system is actually earthed and at what points.

The 10kA fault levels for MCBs seem very high for a residential installation. Have they not heard of fault current limiting?

What "Standard" are they refering to?

What do they mean by "no earth (ground) potentials permitted"? No mention of insulation values which should be a minimum of 1.0 Megohm.

Compare this with AS3000.

Service protective device

MCBs generally a minimum of 3kA.

Main Earth 4.0 sqmm minimum.

Earth electrode 12.7 copper clad steel 1.2M. minimum.

No soil conductivity tests to main earth electrode required.

[elkangorito]

Here are some points for discussion regarding Earthing.

1. Why is earthing carried out ?

2. The function of the PE conductor.

3. The function of the main earth and main earth electrode in an MEN system

4. The function of the main earth and main earth electrode in a TT or IT system.

5. Why must the main earth connection never be disconnected while supply is connected to an electrical installation?

6.When and why must auto disconnection of a protective device occur in the event of an earth fault?

7.Touch voltage and its effects.

8.Equipotential bonding.

David, whilst it is not my wish for this particular thread to be entirely educational (for the non-technical), I do see the merit in discussing some of your points. I cite your points 3, 4 & 8.

Page 15, Table 2.

Size of earth rod in mm squared--------------------Minimum Main Earth sizes in mm squared.

<= 35---------------------------------------------------------------------------------10

35 to 50-----------------------------------------------------------------------------16

50 to 95-----------------------------------------------------------------------------25

95 to 185--------------------------------------------------------------------------35

185 to 300-----------------------------------------------------------------------50

300 to 500-----------------------------------------------------------------------70

> 500---------------------------------------------------------------------------------95

As a result of today's meeting, please amend the above bolded & underlind text as follows:

Active conductor.

The above sizes are for copper conductors only. If aluminium conductors are used (the PEA seem to always use Al conductors), current ratings must be used order to transpose the correctly sized Main Earth conductor.

[elkangorito]

My comments in blue.

It would appear that the earthing arrangements costs are being born by the consumer not by the PEA/MEA in their implementation of the MEN system. These figures of soil resistivity (contact resistance) of 5 ohms and 25 ohms is what might be expected when earthing the neutral of the distribution network. It is not stated if the neutral of the distribution system is actually earthed and at what points.

I'm not quite sure of what you mean when you say, "It would appear that the earthing arrangements costs are being born by the consumer not by the PEA/MEA in their implementation of the MEN system." Please clarify.

I don't think that 'soil resistivity' & 'contact resistance' are the same thing. Please clarify.

The 10kA fault levels for MCBs seem very high for a residential installation. Have they not heard of fault current limiting?

Yes, a 10kA fault level does seem high but knowing the size & type of transformers used by the PEA, it is quite possible, particularly if the installation is very close to the tx. With regard to FCL's, they do use DIN type HRC fuses on the secondary side of 'most' (but certainly not 'all') txers. The type of DIN fuse used is unknown to me.

What "Standard" are they refering to?

I believe that they are not refering to a 'standard' as such but some rules (recommendations?), which appear to be in a book published by the EIT (the Engineering Institute of Thailand). My 'electrical' work colleagues are in the process of some translation with regard to this book.

What do they mean by "no earth (ground) potentials permitted"? No mention of insulation values which should be a minimum of 1.0 Megohm.

This means 'no differing potentials between any 2 points on the surface of the earth'.

Compare this with AS3000.

Service protective device

MCBs generally a minimum of 3kA.

Main Earth 4.0 sqmm minimum.

Earth electrode 12.7 copper clad steel 1.2M. minimum.

No soil conductivity tests to main earth electrode required.

The whole booklet is a recipe for disaster, although it is published with the best of intentions.

I mentioned the contradictions within this book to my Thai 'electrical' colleague. As I anticipated, his response was polite knodding & an otherwise blank look on his face. Although, I must give him some credit...he did recognise that the booklet can't possibly be affective (safe?) unless the method of earthing at the tx is initially realised.

Edited March 29, 2010 by elkangorito

[david96]

Ref to post #19 by Elk.

Costs being born by the consumer not the PEA/MEA regarding implementation of their version of the MEN system. To try and obtain a contact resistance (5 ohms/25ohms) between the earth electrode and the soil surrounding it can be an expensive exercise.

But the electricity distributor carries this out on the distribution system neutral at the transformer earthing may be vertical rods in a trench bonded with a bare copper conductor or alternative means such as horizontal strip electrodes buried at the required depth.

The neutral is bonded to earth along the distribution network by a single copper conductor to an individual earth electrode at regular intervals. This bonding enables the PD between the neutral and earth at close to zero volts as possible.

This is why under AS3000 a depth of 1.2/1.8M with one 12mm copper clad steel electrode is regarded as complying. It in effect just bonds the main neutral to the general mass of earth.

Fault current limiters: These are in effect the service protective device which in most cases is a cartridge type HRC fuse. These fuses may be mounted on a pole, or in a distribution box with underground reticulation. Essentially they protect the consumers mains. They are not for overload protection. They also provide a point to disconnect the electrical installation. This is why one can use 3kA MCBs. and previously before MCBs, rewirable porcelain fuses which had a lower kA rating again.

Short circuit levels are far less on a single phase 220V supply than a 380V bolted 3 phase fault.

"No differing potentials between any two points on the surface of the earth" One might interpret that to mean equipotential bonding in some form. Or do they refer to "touch voltages"?

One would agree with your comments in the last paragraph. Also there is no mention of mandatory testing.

(One used soil resistivity and contact resistance as meaning the same , they are not it is contact resistance with the electrode was what was being refered to and one of the reasons an earth electrode must be exposed to the weather and not be encased in concrete.)

[david96]

On the point of earth electrodes, no mention is made to prove one has achieved the minimum

of 5/25ohms. This requires specialist equipment.

On RCDs, very vague about their implementation and only recomended. If they are genuine

regarding protection they should spend less time on the onerous earthing requirements of a consumers installation and concentrate on the mandatory installation of RCDs instead.

HRC fuses will clear a short circuit fault of high magnitude much faster than a MCB/MCCB.

This is why most DSBs in many large electrical installations are specified with 6kA MCBs. The sub mains supplying them may be 250A or 160A but they are protected by CFS units with HRC fuses on the main switch board which may have a rating of 50kA.

With an HRC fuse protecting the consumers mains one can use MCBs with far lower short circuit ratings. Means lower costs for an electrical installation, and protection is not compromised.

The most logical place to install HRC fuses to protect consumers mains in Thailand would be on the line side of the PEA/MEA metering point.

[Khonwan]

......

The neutral is bonded to earth along the distribution network by a single copper conductor to an individual earth electrode at regular intervals. This bonding enables the PD between the neutral and earth at close to zero volts as possible.

...

Interesting thread. Just a minor observation: in my PEA area, the neutral is bonded to earth (I think every 200 metres) by aluminium cable to a galvanised earth rod - I've never seen copper being used here.

[david96]

......

The neutral is bonded to earth along the distribution network by a single copper conductor to an individual earth electrode at regular intervals. This bonding enables the PD between the neutral and earth at close to zero volts as possible.

...

Interesting thread. Just a minor observation: in my PEA area, the neutral is bonded to earth (I think every 200 metres) by aluminium cable to a galvanised earth rod - I've never seen copper being used here.

It was in Australia one was refering to as a typical well implemented MEN system. Copper is used and the minimum MEN conductor on the distribution system is generally 16sqmm to a copper clad steel electrode.

[david96]

MCBs and fault current ratings.

MCBs up to 100A are generally of a common frame size, examples are the Terasaki SAF-T, the Heinmann CF, and the Eaton QC range. They all have a common fault current rating of 6kA. This is based at 380/440V 50Hz. They are the standard MCB used in electrical installations. Fixed overcurrent and earth fault tripping, Curves B, C and D. Curve C is the most widely used for lighting and power circuits. Standard curve is C.

The other standard is the European pattern known as DIN. They are smaller physically and are manufactured up to 100A in 3kA, 4.5kA, 6kA and 10kA. but will fit in a common panel board or loadcentre. They also have fixed overcurrent and earth tripping features. Available in curves B,C, and D.

Over 100A and the fault level of these devices increases and they are kown as MCCBs.

These may have adjustable tripping characteristics and earth leakage modules may also be fitted, 0.3ma to 10A with time delays 0 /0.5/1.0 sec. These MCCBs are used on large main switchboards etc. They are used on subcircuits that have a high fault current at the switchboard. They are expensive. HRC fuse switches are the alternative.

Circuit breaker manufacturers will type test their products with a recognised testing authority and the kA ratings will be given for different voltages and frequencies.

A MCB may be rated at 6kA for 380V and could be 10kA for 220V. In othe words if one uses a 6kA MCB it would comply.

Those Square D MCBs available in Thailand are almost identical to the Eaton QC range. The QC range originated from Westinghouse in the USA.

[elkangorito]

My comments in blue.

Ref to post #19 by Elk.

Costs being born by the consumer not the PEA/MEA regarding implementation of their version of the MEN system. To try and obtain a contact resistance (5 ohms/25ohms) between the earth electrode and the soil surrounding it can be an expensive exercise.

I'm still not sure what you mean by this but in Australia, the consumer has to pay for all electrical work with regard to the consumer's property. Of course, this includes anything that relates to 'earthing'.

The 'energy authority' is responsible for their own connections at the transformer.

But the electricity distributor carries this out on the distribution system neutral at the transformer earthing may be vertical rods in a trench bonded with a bare copper conductor or alternative means such as horizontal strip electrodes buried at the required depth.

The neutral is bonded to earth along the distribution network by a single copper conductor to an individual earth electrode at regular intervals. This bonding enables the PD between the neutral and earth at close to zero volts as possible.

The cable type is irrelevant. The most important point is "how is this cable 'earthed'?". Usually, the 'earth' from the 'star point' neutral is vertical.

This is why under AS3000 a depth of 1.2/1.8M with one 12mm copper clad steel electrode is regarded as complying. It in effect just bonds the main neutral to the general mass of earth.

The above only pertains to the earth stake at the individual domestic installation. I say this because some people may be confused with the difference between the 'star point earth at the transformer' & the 'earth stake within the domestic property'.

"No differing potentials between any two points on the surface of the earth" One might interpret that to mean equipotential bonding in some form. Or do they refer to "touch voltages"?

This means that if anybody walks around on the earth (ground/soil) outside, they will not be subject to electric shocks.

Interesting thread. Just a minor observation: in my PEA area, the neutral is bonded to earth (I think every 200 metres) by aluminium cable to a galvanised earth rod - I've never seen copper being used here.

As above, it is not important what type of cable is used in this regard.

David, could you please refrain from posting 'the obvious'? I say this purely to aid simplicity as most of us here will be (& are) familiar with many things electrical. If someone is not familiar with 'many things electrical', they can obviously ask questions or make comments....like Khonwan did as above.

[Khonwan]

My comments in blue.

....

Interesting thread. Just a minor observation: in my PEA area, the neutral is bonded to earth (I think every 200 metres) by aluminium cable to a galvanised earth rod - I've never seen copper being used here.

As above, it is not important what type of cable is used in this regard.

David, could you please refrain from posting 'the obvious'? I say this purely to aid simplicity as most of us here will be (& are) familiar with many things electrical. If someone is not familiar with 'many things electrical', they can obviously ask questions or make comments....like Khonwan did as above.

Please do not be so pompous. I am (and was) perfectly aware that it matters not whether copper or aluminum is used. I was simply making an observation since it appeared to me (and still does) that David was referring to the systems employed in Thailand. I’m not an electrician but I have had a fair amount of experience installing my own 3-phase system over a distance of one mile without your assistance or that of any other electrician.

If you don’t want comments from non-electricians, take your discussion to one of the many electrical forums outwith ThaiVisa.com!

[david96]

In reply to post #25 by Elk.

I think you misunderstood me, in Australia the electrical contractor installs a 12mm copper clad steel earth electrode at the electrical installation. This takes about 15mins to drive in average soil, and terminate the main earth conductor in an approved manner. This complies with AS3000. The main earth conductor from the electrode must not exceed 0.5 ohms. It is the main earth conductor that is tested for compliance not the electrode /soil resistance.

The Electrical Authority is responsible for earthing the neutral conductor at the transformer and at regular intervals on the network, they bear this cost and are responsible for compliance

with their own requirements. The electrical contractor knows that the MEN system is mandatory.

In Thailand the guide lines are 5/25ohms resistance between the soil and the electrode and 2 or more electrodes may be required driven 2.4 metres. To verify this would require testing with an earth resistance tester. It is in my opinion that this is not required with a MEN system, and all that is required in a single electrode 12mm copper clad steel minimum driven to a depth of 1.2M minimum. This is for the consumers electrical installation only.

Earthing at the transformer is generally with vertically driven electrodes but strip electrodes run horizontally may be employed in some cases. In Australia the point of earthing is the neutral terminal of the transformer on the public network.

The Thailand the demarcation line between the electricity authority and the consumers electrical installation is not clear but for all practical purposes would be at the metering point. From this point on is known as the electrical installation.

"No differing potentials at any two points on the earth surface"

What is meant here is known as "Ground gradient" which creates two other problems, "Step potential" and "Touch voltage"

Step potential means the prospective or open circuit voltage that may appear between any two points ( 1 metre apart ) on the surface of the ground. Step voltage reduces substantially at short distaces from the grounding point. A guide is that the voltage will halve for each 0.75 to 1 metre from the grounding point.

An Earth spike is not the same as an Earth electrode. The terminology can be confusing.

[david96]

I forgot to mention the step voltage and touch voltage only appear when there is an earth fault.

Fallen power lines will cause step voltages to appear.

[elkangorito]

Just visited a place in Ban Chang yesterday (said 'Bun Chung') near Rayong. I saw 2 transformers that were IT connected.

It appears to me that many parts of Thailand are NOT TT connected.

Edited June 20, 2010 by elkangorito