GFI in a split-phase 230V system without neutral wire?

[mbrooke]

All service drops here really only have two wires; the transformer ground/neutral is not connected to the home.

A German engineering firm made a study (pdf) of public LV-network technologies, detailed in the following diagrams:

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The POCO in our city utilizes Configuration A. The comments in the engineering study: They do not mention, that this configuration violates the electrical code, only that it is "quite unique":huh:. After reading up on various earthing systems and gaining a little more understanding, this looks similar to a TT earthing system to me as well, which mbrooke already mentioned:


Schneider electric has an informative article titled "earthing systems worldwide and evolutions" (pdf), concluding: "future evolution should favour earthing systems generating fault currents which do not exceed a few dozen amps. TT earthing systems should therefore be increasingly used."

Based on our discussion and the above info I would conclude:

1. Configuration A is the POCO's standard connection for millions of residences around the country. They are unlikely to change it just for us, even if it may violate the national code (PEC 2009). Possibly they interpret the code differently.
2. A TT earthing system is inherently unsafe when used with merely regular two pole circuit breakers, as commonly done here.
3. For safe operation, the above configuration needs the main breaker and every branch circuit to be secured by GFCI/RCD breakers, possibly using multiple levels as described by Schneider Electric for TT systems here
4. Using the correct two pole GFCI breakers, such a system, should be able to function reliably.

Do you think my conclusions are correct?

You are correct, in order for configuration A to function it would need RCD on all circuits. Not having RCD is very dangerous, both a fire and electrocution hazard. The fact regular 2 pole breakers are used shows a huge lack of understanding by those who do it.

My guess is the poco does not give a ground/neutral wire to save money. Either they need to start giving functional ground wires or TT earthing needs to be implemented correctly.

I would call the power company and explain your concern telling them why its dangerous. They might understand and drop a neutral wire. Also show them the code as well.


Just to add, in TT earthling some electrician do recommend 2 GFCIs in series just in case if one fails another can back it up.

 

[kwired]

You are correct, in order for configuration A to function it would need RCD on all circuits. Not having RCD is very dangerous, both a fire and electrocution hazard. The fact regular 2 pole breakers are used shows a huge lack of understanding by those who do it.

Can't say how the legal system works at the OP's location, but in the US, there is all kinds of room for potential lawsuits if you are the POCO doing those same installations. Winning or losing the lawsuit may not matter, but most businesses goals outside of law practice firms are to keep out of litigation in the first place as it is not what they are in business to do.

 

[mbrooke]

Can't say how the legal system works at the OP's location, but in the US, there is all kinds of room for potential lawsuits if you are the POCO doing those same installations. Winning or losing the lawsuit may not matter, but most businesses goals outside of law practice firms are to keep out of litigation in the first place as it is not what they are in business to do.

In the US and Canada it certainly isn't allowed under the CEC, NEC or NESC for LV power even with GFCI breakers. Not to mention most of our GFCI breaker contain electronics so one good voltage spike will leave the system unprotected without indication.

TT earthing is allowed in the IEC as long as appropriate installation practices are followed. However, even then TT earthing is generally found on older existing supplies with them gradually being changed over to TN. In the OPs case the neutral is close by along with being a real EGC since it will not be used for load. Not running it to the structure is very counter productive.