My consumer unit keeps tripping, is this connected to the smart meter?

There is evidence that the response to polling the meter for data - as happens twice each night, once for readings and once for usage data - can cause an RCD to trip, for example: https://www.electriciansforums.net/threads/rcd-tripping-straight-after-smart-meter-install.200818/post-1783565 

The two remedies I’ve seen involve (a) replacing the breaker that trips with a new, higher-spec one, and (b) moving the meter further away from the CU. A third which I’ve not seen tested but may be worth investigating: replacing a plastic CU enclosure with a metal one. If the CU is old and perhaps not up-to-code any more, this might be a longer-term solution. Sadly, it’s not a cheap option.
 

Thank you for your suggestions.

I will discuss them with the electrician tomorrow, hopefully he will find a solution. I will post result.

Thank you

​@Firedog At first I was going to dismiss your suggestion of the meter polling but as a radio engineer it does have some merit and we are staring at the bottom of the barrel and possibly the electrician too. ​@Jan71 has already said the RCD has been replaced so it's unlikely to be fault.

Puts on radio engineer hat

There may be some kind of resonant circuit going on here (feasible but I'm thinking unlikely) where the proximity of the meter to the wire run to that RCD and the exact length of that wire is the factor. How do we fix that? Reroute that wire away from the meter if it passes close to it?

Ok.

1) Have the electrician check the insulation on that ring final circuit

2) If ok, check to see if the cable from that RCD passes close to the meter. If so reroute it even if on a temporary basis

3) As a test, add a choke on the cable associated with the RCD. You make one of these by taking some small guage, insulated solid core wire (one of the wires in a twin and earth for example) and wind about 10 turns around the cable and make a connection between the two ends. Insulate the whole thing. It needs to be close to the RCD. If that fixes it then it is the transmitter in the smart meter causing it. The electrician will have to find another solution. The choke is only proving a point. I doubt if it can remain there.

To be honest I've never heard of this happening before but radio is a strange beast and it can do weird things given enough power.

Peter

Thanks for your insight, ​@Peter E . 

It was my understanding that an RCD works by detecting any tiny bit of EMF radiation emitted from a nearby coil through which current only passes if there is an imbalance. If it’s designed to detect tiny bits of radiation, then is it impossible to imagine that a sudden transmission burst from a smart meter’s comms hub could generate enough to trigger the RCD? How else would you explain tripping that stops when the RCD is replaced by one with a higher spec?

Yes. RCDs work by looking for the difference in currents between the live and the neutral at 50Hz. What a sufficiently high level of RF could do is spoof / replicate the level of imbalance such that it trips. Normally, the level of RF is low enough not to cause a problem but if you have a resonant length of wire passing near to the smart meter communications hub then it could cause an issue but I've never heard of it before in this context but I have seen it elsewhere and had to fix the issue.

Interesting conversation.

Would I be right in thinking that the length of the wire is significant to the resonance, ie. simply replacing it with a shorter or longer wire would change the resonance and thus cure the issue?
Or would it take more than?

Spot on. The resonant length is dependent on the frequency. At 300MHz the wavelength is one metre. The resonant length is a quarter wavelength or an odd multiple thereof. We call these resonant lengths aerials because that is exactly what they are. So you can see that even short lengths of wire have the capacity to couple efficiently into the smart meter transmitter aerial.

It's further complicated if you have a 3G signal system because the mobile phone basestation will ask the smart meter to shout louder (transmit at a higher power level) if the signal it is receiving is low because it's buried inside a house. I think radio systems in the north have a fixed power.

Hi All,

Just to let you know the electrician came and moved the sockets to the other side of the board,  so nothing on the rcd side now.

The RCD has tripped again at 03.50, so am I right to think it is the smart meter transmitting.  I have a plastic CU so thinking it will need to be changed for a metal one.

A question that may help get to the bottom of this:

How do you know that it tripped at 03.50?
Presumably you were in bed asleep, so what is telling you it tripped at that particular time?

PS. If there is nothing on that RCD now then does it matter for the moment whether it trips out? You could just leave it off.

Hi ​@Jan71 thanks for continuing with the feedback. That is really useful.The metal enclosure should help and it's a good move anyway. I hope it fixes the issue.

Does the cable for the RCD that trips pass near to the smart meter? If it does then would there be a possibilty of rerouting the cable as a lower cost alternative?

Peter