Earthing the Neutral?

Hello Phil,

I'm a sparky over here in Spain and work on the lines aswell as house installations and industrial installations etc...

Anyway, Normally there should be an earth spike at your post (where the general fuse box is) which is connected to the neutral halfway up the post (if it's a concrete post) Or if there are other posts near by which have other houses connected to them, they may have the earth spike! Most long OHL's have multiple earth spikes along the line so as to bleed off any unwanted voltage! You might want to get in touch with your supplier to check that your line is still in good shape! If the 60v is in their line, it may mean they have a bad connection (which would not surprise me in the slightest!!) If the line turns out to be OK ie. 0v to earth at the meter, then I would check the wiring in the house for any problems!

Anyway, Good luck and if you are in the Almeria area give me a PM (private message) and I'll pop over to check it out for you.

Hi - thanks for your reply!

I'm pretty sure there is no earth connection whatsoever at the tower, though I will double-check that in the morning. I could quite easily earth the incoming neutral at the consumer unit upstream of the RCD, and this should certainly cure my 60v problem. My only concern was that this might have some adverse effect on the phase or - worse - somehow result in my meter registering more usage than I was actually getting!

Sorry if this sounds a bit naive, especially as I am actually an electronics engineer! It's the old story of a little learning being a dangerous thing - this simply isn't an area in which I have any practical expertise.

And unfortunately, I'm in the Malaga area, so I'm afraid that pint I would have bought you will have to wait!

Hi Phil,

Shame about the pint but in any case ring the supplier. It's their duty to provide you with a safe electrical supply. I really sounds like it's the neutral connection at the transformer which is their responsibility. I would not ground out your neutral at your board in case there is a neutral fault in the line and your little connection to earth takes the full brunt! Inform the supplier!

Anyway, welcome to CR4 and I hope you enjoy your stay

<...connected to about 200m of reinforcing rods in the house foundations...>

So it's not actually a proper earth electrode network, then?

<...it always trips the RCD if neutral touches earth, even when MCB is off...>

Then the RCD is doing its job. The neutral and earth should not be touching downstream of the RCD. If they are, then this is a fault, which wants correcting.

<...Could/should I earth the neutral at either the consumer unit or the pylon/electricity meter (about 200m away) or both?...>

No. This sort of thing is the responsibility of the utility supply company. There are safety and criminal law issues involved in tampering with their equipment. There are civil law implications should one's actions disrupt the supply of others as a result of tampering with their equipment.

<...prefer it to be 0v...>

It is of no consequence to the user in a correctly-installed and well-maintained system. The voltage between earth and neutral will never be exactly 0V, as other users' demands elsewhere on the network will affect the crrent flowing in the neutral and therefore the voltage on it. In a fault-free installation, there will be no need to measure it!

If in doubt, consult an appropriately-qualified electrician locally.

This Earthing method is now common practice in Spain! The house earth is connected to the the base slab reinforcement bars and also a 1.5m Earth rod through 35mm² unsheathed copper cable.

At the transformer, the neutral normally has 15m of 50mm² u/s copper cable connected to five 2m earthing rods, and the earth is a network of six 2m rods in a ring around the transformer housing. Both these connections go back to their appropriate connection inside the transformer housing! It's normally the connection of the neutral spikes inside the transformer housing that works loose when somebody uses an incorrect terminal or a nut and bolt made out of mild steel. A bit of electrolysis later and the neutral starts to fail!

• <...connected to about 200m of reinforcing rods in the house foundations...>

• So it's not actually a proper earth electrode network, then?

I'm not quite sure what you are implying here! Is this a simple question, or are you saying "so it's not much good as an earth, then?"

• <...it always trips the RCD if neutral touches earth, even when MCB is off...>

• Then the RCD is doing its job. The neutral and earth should not be touching downstream of the RCD. If they are, then this is a fault, which wants correcting.

Indeed! The problem arises if, for example, I need to make an addition to a lighting circuit. I kill the MCB for the circuit to make it safe, but if I inadvertently manage to let earth and neutral touch while I am wiring, the RCD trips, which knocks everything off. This is a pain. If neutral were to be earthed at the CU, then there should be insufficient current to trip the RCD, no?

• <...Could/should I earth the neutral at either the consumer unit or the pylon/electricity meter (about 200m away) or both?...>

• No. This sort of thing is the responsibility of the utility supply company. There are safety and criminal law issues involved in tampering with their equipment. There are civil law implications should one's actions disrupt the supply of others as a result of tampering with their equipment.

Understood - and in UK I would get the company in to fix it - however, it would probably not have arisen in the first place in the UK. This is Spain - things are different here!

• <...prefer it to be 0v...>

• It is of no consequence to the user in a correctly-installed and well-maintained system. The voltage between earth and neutral will never be exactly 0V, as other users' demands elsewhere on the network will affect the crrent flowing in the neutral and therefore the voltage on it. In a fault-free installation, there will be no need to measure it!

Unless it is grounded at the CU, surely? I don't see how upstream currents could affect my neutral-ground PD in this case. Enlighten me! And as for being of no consequence, I offer the example of changing a light bulb (ES out here) Even if correctly wired, it's very easy to touch the neutral when changing a bulb. A significant neutral-earth PD could, I suggest, have consequences.

• If in doubt, consult an appropriately-qualified electrician locally.

See above!

But thanks for your responses. One never stops learning!

60V at neutral is a bit too much, and needs correction.

In Indian Electricity act, If I am not wrong, the statement is

"The neutral point of a 3 ph, 4 wire system shall be earthed at elast at two distinct places at generating station and substation...

It may also be earthed at one or more point along the distribution system or service line in addition to any connection which may be required at consumer's end.

So it does not prohibit the earthing of neutral.

But be careful about the RCD of the supply transformer tripping as well as the heavy current that your earth may have to dissipate.

Interesting. Thank you.

Why not put a small isolating transformer? No act will prohibit earthing its secondary neutral.

Another interesting thought - though a 10kVA isolating transformer probably wouldn't be that small! Or cheap!!