electau

It sounds that the fault is caused by moisture, on a termination. It is unlikely the cable has been damaged. Check the connections first. Noise on the line is the indication.

The generator MUST NOT be connected in such a way so as generator output can be fed back into the PEA distribution network.

You will require a manual change over switch preferably with an OFF position. 1-0-2.

As a matter of interest is the main neutral of your electrical installation earthed to an electrode or is there no earthing and electrode?

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.

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.

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.

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.

The load centre appears to be a US pattern (NEMA) with plug in protective devices. Yes it is a split unit as nonprotected (MCB only) and protected (RCD with MCBs).

I note that there is no earth (ground) bar.

This might explain the neutral earthing that is implimented in Thailand in that it may originate from the USA. (NEMA).

If the main switch is an 63A MCB this will provide the short circuit and overload protection. The actual current rating of the RCD can be 63A or 40A. Generally protection on the line side is up to 100A. The max size of the protective device on the line side is usually indicated on the RCD.

I used 10 of them as a trial in 2004. Clipsal 2000 series. was not impressed with them. Screw type terminals were preferred. never used them again. There are terminals displacement type with a punch down tool for power control circuit connection made by Krone.

Yes one had to strip 13mm of insulation and insert wire, 2 wires per fitting.(loop in / loopout)

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.

Known as insulation displacement type terminals. They are an option to use instead of screw type terminals. Clipsal (Aust) have had them on there 10A outlets since 2004 as an optional product to the standard screw version. The time taken to teminate a socket outlet is less than if a screw type is used. Might be important if you are an electrical contractor terminating a large number of outlets in an installation.

IMO the screw type terminal is preferable.

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.

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.

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.

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.

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

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).

Yes Crossy I have been in Thailand.

No, I have never had a meter with 100% overload except perhaps under test conditions.

With installation design that problem would be ruled out. Overload capability should be in the meter manufacturers specifications

First one should disconnect the conductors from the RCBO and with an insulation tester 250/500V check the insulation to earth This should be above 1 megohm. L and N .

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.

The main switch should be on or adjacent to the main switch board. In Thailand this should be a 60 or 63A MCB rated at 10kA at 220V.

eg. a Square D MCB.

The PEA will decide what the metering size will be depending on your max demand in amps.

The max demand may be the rating of the main circuit breaker (60/63A). the standard meter now is 15/45A 220V 400 rev per kWh. Meters can sustain 100% overloads.

An auto main switch is a standard MCB. An RCD is a not an MCB, An RCBO is a combination RCD and MCB.

You should not use a ring main. Use a star connected system with main switchboard and distribution boards. Final subcircuits run off the switchboards. Install RCD protection and TT earthing.

Ref #693

Service fuses are not used in Thailand. Metering is on the line side off the main switch.

The reference here is to a 63A main circuit breaker. This will give overload protection of the mains and short circuit protection on the load side of the MCB. Your mains should be PVC/PVC.

Service fuses are to protect the mains and metering from short circuit and are a disconnection point for supply. They are supplied by the electricity authority.