Solar panel wiring.

[minimutly]

It will be G98/99 now and I think the requirement is 0.5s for loss of mains.

DNOs have a bit of a balancing act, fast safe disconnection is obvious but unfortunately tight tolerances that trip out all local inverters could cascade into a serious problem so they need to consider this and maintain a fault ride through ability.

The new G99 regs are causing me a headache - where I have a rotating generator synched to the mains, there is a momentary loss, or brown out, and the generator loses synch - bang, out goes the current breaker. Looks like the regs applied to inverters and wind turbines works better, but for a water turbine it loses us more than we gain, ultimately an overcurrent trip is a site visit...

 

[J1nx]

Solar farms suffer the same, most under the old G59, they trip the HV and then it needs HV SAP attendance, not a cheap exercise when the guy available inevitably has to travel 4 hours plus

 

[dobbslc]

Wow we've got from what cable to run from the roof to tripping HV sub stations

 

[J1nx]

Least it took until the second page! That’s good going for here and not a YouTube in sight!

 

[Dave-sparks]

This is why I never understood why it was considered acceptable to backfeed through an MCB into the consumer unit - pretty much makes the RCD redundant as the busbar will still be live for potentially several seconds before the inverter registers the loss of the grid.
I suppose if they are all RCBOs it might not be so bad, but I've seen plenty of single RCD and split load boards done this way.

It is not considered acceptable to connect the solar circuit to an RCD which is shared with any other circuit.

An MCB or fuse is very different to an RCD and will still provide adequate protection.

 

[Dave-sparks]

Er no, the inverter is (usually) bound by the G83 type approved regulations that mean it trips allmost instantaneously. Not sure if the newer ones are slower, but I wouldn't be suprised though.

'almost instantaneous' is not good enough for protection against electric shock.
That 'almost instantaneous' operation only occurs after the RCD has tripped so is adding a further delay after the point at which the electric shock should have been stopped.

 

[minimutly]

'almost instantaneous' is not good enough for protection against electric shock.
That 'almost instantaneous' operation only occurs after the RCD has tripped so is adding a further delay after the point at which the electric shock should have been stopped.

Actually, you are quite correct, it would negate the fast reaction of an rcd, assuming the rcd was tripped to prevent execution.

 

[Gareth J]

The new G99 regs are causing me a headache - where I have a rotating generator synched to the mains, there is a momentary loss, or brown out, and the generator loses synch - bang, out goes the current breaker. Looks like the regs applied to inverters and wind turbines works better, but for a water turbine it loses us more than we gain, ultimately an overcurrent trip is a site visit...

What sort of water turbine do you have, if you don't mind me asking?

 

[MetalMonkey]

Er no, the inverter is (usually) bound by the G83 type approved regulations that mean it trips allmost instantaneously. Not sure if the newer ones are slower, but I wouldn't be suprised though.

It's a fair point, seconds might have been an exaggeration, for some reason i was thinking of 5 seconds but that might be for something else.
But even 0.5 seconds is several times the acceptable trip time for an RCD, so the busbar is still live with the RCD tripped until the inverter shuts off.

It is not considered acceptable to connect the solar circuit to an RCD which is shared with any other circuit.

An MCB or fuse is very different to an RCD and will still provide adequate protection.

It must have been acceptable at some point as that's how all the ones I've seen have been connected. Signed off by MCS accredited electricians for the FIT.
Slap a (usually mismatched) MCB in a spare way of the consumer unit, back feed through the main RCD, no need to break the tails.
Must have been thousands installed that way up and down the country.

I just had a quick look and it seems like there was at one point a reg to address it (712.411.3.2.1.1), but that seems to have been removed now, closest I can find in the brown book is 712.551.7.2 which doesn't specifically mention RCD unless I missed it.

 

[minimutly]

Actually, you are quite correct, it would negate the fast reaction of an rcd, assuming the rcd was tripped to prevent execution.

Lol, electrocution...

 

[minimutly]

What sort of water turbine do you have, if you don't mind me asking?

I don't have one, but have project managed the installation of a number, and now look after a fleet of them - from 60 to 2500kW, all driven by water.

 

[Erie Fred]

Are they using normal household RCD's on D.C. ?

 

[qwakers]

Lol, electrocution...

nah i think you where right first time...

 

[J1nx]

Are they using normal household RCD's on D.C. ?

No, most domestic installs use no protection on that side. Industrial use something like a Bender (no sniggers at the back!) ground fault monitor relay.
Riso faults as they are often called are common place but often go undetected until really bad, this is why string testing with a Seaward is often recommended annually.