Definitions -- terms like TT / TT-S-C

[SunshineHarvey7]

I'm doing some research on grounding. Can someone please give me the definition of TT? And TT-S-C? (I think I read these acronyms on an electrical forum but haven't found a definition.)

 

[sometimewoodworker]

 

it is TN-C-S  PME

 

[userabcd]

They are earthing methods for eg.

 

What Is TT Earthing System?

The TT method refers to a protective system that directly grounds the metal housing of an electrical device, which is called a protective earthing system, also called a TT system. The first symbol T indicates that the neutral point of the power system is directly grounded; the second symbol T indicates that the conductive part of the load device that is not exposed to the live body is directly connected to the ground, regardless of how the system is grounded. All grounding of the load in the TT system is called protective grounding. The characteristics of this power supply system are as follows.

 

Refer earthing systems

[Crossy]

Wikipedia has an explanation of all the various flavours of earthing systems https://en.wikipedia.org/wiki/Earthing_system

 

To expand on STWW's post Thailand is TNC-S with MEN or PME (for our purposes the same thing).

 

You MUST wire your incoming supply as in this diagram if you want to pass a PEA/MEA inspection. Note the routing of the incoming neutral.

 

Drawing is from this handy PEA document which you can show your contractor Groundwire Mk2 book-Manual.pdf

 

 

 

 

Once you have a permanent supply (4.x Baht per unit) you can do pretty much what you like, so if you really love TT then go for it.

 

[SunshineHarvey7]

Thanks everyone for your input. The Wikipedia article seemed quite helpful.

[Led Lolly Yellow Lolly]

I nearly ALL cases in Thailand (99.9999999999 percent (made up figure)) you'll be wiring up as TNC-S with MEN but you absolutely MUST be sure that your local supply is set up in this way because the consequences can be disaterous if you do TNC-S with MEN but your local system is something else.

 

If you already passed the PEA/MEA check, you can basically do whatever you want (within safe reasoning of course). Personally I have my own home wired as TT for a couple of reasons. I object to the risk of a broken neutral and I prefer the low noise of such a system (I have a lot of audio and IT stuff running).

 

Kudos to you for trying to sort things out yourself, you won't find much competent help otherwise.

 

 

 

[Led Lolly Yellow Lolly]

. . . Forgot to mention, you will find many TNC-S MEN systems in Thailand that only have overcurrent protection. It is legal requirement now to have residual current protection installed with TNC-S MEN. If you take the TT route, residual current protection is and always has been prerequisite. DO NOT skip the RCD protection with TT.

 

Switching between TT and TNC-S-MEN is trivial if you know what you're doing, so if you take one route it's not hard to change to the other.