Electrical Information Thailand.

[electau]

Useful Information. Electrical Installations in General. Thailand.

A customers electrical installation commences from the point of supply. This is generally the energy metering point in Thailand. The LV transformer, distribution conductors, protective devices, service fuses( if installed) and metering are the responsibility of the PEA/MEA.

With any electrical installation one must calculate the max demand in amps first. this can be done by calculation or by the setting of a fixed current MCB. In Thailand service fuses are not generally installed, they protect the consumers mains from short circuit and provide a point of disconnection for the installation. They are not for overload protection. In Thailand a double pole fixed setting MCB is installed, this setting is the max demand of the installation. It also provides short circuit protection on the load side of this MCB. This MCB is generally rated at 6kA at 380V and 10kA at 220V. MCBs for submains and final subcircuits are generally a max of 6kA (1.5kA min). These are prospective short circuit ratings.

Most MCBs will be known as C curve for lighting and power circuits. other types are B and D but these are not used in residential type installations in general.

An MCB must trip on an earth fault in less than 0.4secs, hold a current of 1.2 X rated FL current continuously and must trip at 1.45 X FL current.

An 30mA RCD or an RCBO must trip in less than 0.3 secs at rated trip current in mA on an earth fault.

An 10mA RCD must trip in less than 0.04 secs at rated current on an earth fault.

Conductor installation must satisfy current-carrying capacity, voltage drop and other minimum size requirements for conductors.

With an MEN (TN-C-S) earthing system the earth loop impedance must be low enough to trip an MCB with in the required times. In practice this loop impedance will not be a problem as the requirement of voltage drop will require the installation of larger conductors, thus lowering the loop impedance.

With the TT or direct system of earthing the earth loop impedance will always be high and that is why RCDs must be used for earth fault protection.

Automatic disconection by a protective device must occur if the touch voltage exceeds 50VAC.

Thailand uses both the TT or direct earthing. The MEN system is also used as an option in new installations. Most Thai electrical installations use direct earthing. Mixing of TT and MEN is permitted within an electrical installation.

RCBOs are used as a main switch, thus giving protection to earth faults within an installation, a cost effective way of minimum protection without installing a compliant earthing system.

[Crossy]

Fixed the topic title electau.

I'm assuming most of your quotes are from the Oz regs which, whilst a good fit for local conditions, are not enforceable.

[electau]

Fixed the topic title electau.

I'm assuming most of your quotes are from the Oz regs which, whilst a good fit for local conditions, are not enforceable.

Thanks Crossy.

The MCB and RCD information is from AS/NZ3000. The TT system is not used under AS3000.

Information supplied is for guidance purposes only. As you stated BS, IEC or AS/NZ3000 standards are not legally enforceable in Thailand.

Edited August 16, 2011 by electau

[Crossy]

Over the years there have been sporadic efforts to find a local set of domestic installation regs.

Electau's predecessor as Resident Aussie Sparks (elkangorito) failed miserably in his quest, perhaps electau would like to take on the challenge

One useful document we did find was this PEA pamphlet http://www.pea.co.th/pdf/groundwire.pdf

Another electrical safety pamphlet from the same source http://www.pea.co.th/pdf/SB-B02-5001.pdf

[electau]

Yes Crossy, I too have tried to access a document pertaining to wiring rules in Thailand. I was able to access the Malaysian standard, they use the TT earthing system and RCDs and they are based on British Standards.

But not Thailand outside of those two PEA documents which are in effect advice for a consumer, the consumer shows this to their electrician and they then comply with the PEA requirements.

From this document it would seem that the (some) following requirements apply.

Minimum size of main earth 10sqmm. MEN connection.

A 2 meter earth electrode.

An RCBO can be used as a main switch. Short circuit rating minimum 10kA at 220V.

Consumers mains minimum size 10sqmm.

3 pin socket outlets to be installed.

PE earthing conductor to be 1.5 or 2.5 sqmm minimum.

One does not see the justification for a 10sqmm main earth (on a MEN system) perhaps the 10sqmm refers to the main earth of a TT system. 10sqmm is used in Malaysia.

It would appear that whoever authored these documents in the first instance might have sourced their information from an engineering textbook, perhaps based on VDE or NEMA requirements.

Nothing about calculating max demand or voltage drop requirements within an electrical installation.

Perhaps cable current ratings and voltage drop requirements may be accessed from Thai cable manufacturers in their cable specifications.

Edited August 16, 2011 by electau