Demonstrating the impact of DC leakage in Type AC RCDs

[@dsesuk]

Nicely presented Mr Ninja.

[@Firecul]

That's a nice demonstration of the problem with AC breakers. I didn't realise it was quite that much of an effect

[@akilaravi1]

Excellent SparkyNinja.

[@ashmanelectricalservices4318]

Nice to have you back Dave 👍

[@hartleymclaren3210]

Great practical demonstration, struggle with theory sometimes. 👍

[@dimitrisblane6368]

Amazing mate thank you. Finally I get to see the effect of DC earth leakage!

[@ryanatkins3013]

Good vid sparky ninja keep up the good vids

[@e5Group]

That’s our buddy 👍👍👍👍👍

[@matthewdale956]

Why are the wholesalers still selling them then...cost? Reg amendment needed?

[@irfp460]

Because they are cheaper, as he said, they are illegal in continental Europe.

[@pauljones908]

Brillient example of saturation thanks. Just wait until we all need EMC filters on the incomers and active harmonic filters on the network to counteract the harmonic distortion on the network from all of the DC rectification lol! 😂

[@stevechadwick180]

Hi Sparkie Ninja, Great demonstration and wondered if I could get a wiring diagram to make a similar rig to demonstrate this in Australia to Electrical apprentices. Cheers Steve

[@g6electrical847]

Another great video explains the issue

[@hackwoodelectrical]

Only just come across this video… interesting results and very eye opening. How easy it for a typical domestic installation to generate 50mA of DC leakage?

[@jamesmoon5632]

Great info thanks for doing this

[@kelvinroberts9014]

This is an excellent demonstration thank you very much.

[@simonmuggleton4685]

I have a board with 12x Proteus b type ac rcbos . The A type rcbo is currently not available from cef . Should I be concerned yet or will they come out soon to swap a few. All trip buttons work and test well at present

[@markhorton8578]

SparkNinja, please could you explain how DC gets back into the neutral. Almost all PSU's in all equipment begin with an isolating transformer. So getting a pulsed "dc" signal back that way is not impossible but tricky. (Pulses only occurring on one side of the cycle). Beyond the PSU there is often a capacitor and very high resistance resistor to the chassis to prevent charges building and that would provide a very small current to earth. (In fact this used to be the cause of quite high earth currents in large office buildings.) Please could you direct me to, or give examples of how DC gets into the neutral?

[@nicolajkl]

Did you ever find an explanation? I'm looking for one myself.

[@markhorton8578]

@@nicolajkl No. Though I can see how low cost switched supplies could load and distort one half of the ac to create an "artificial DC" I have not seen any clear papers or videos.

[@kgparmod]

I was also wondering...Did u find the answer

[@markhorton8578]

@@kgparmod No except you can produce the effect of DC by chopping the AC waveform, as in transformerless power supplies of the switched mode type, and low cost single sided psu's which usually only use the positive going cycle. This distorts the sinewave lifting the center point above 0v. I knew that anyway, but am still skeptical about it being a common problem, because I cannot find published figures for real word examples. I wonder if it is marketing, for a problem which is only significant in rare conditions, like demonstration equipment. After all, if it IS such a problem, why wouldn't you show real world examples? I have seen such bias induced on railway signal equipment, but given the induction on miles of cable this is not surprising.

[@markhorton8578]

@@kgparmod Not really. Being a ex= industrial electronics/electrical test engineer/manger I already knew that you can give the effect of a DC current by chopping and loading one half of the cycle. (why the equipment designers always go for the rising side I do not know, its dumb.) Anyway for domestic stuff the effect should be very small. At the time of this video I searched a LOT for real world figures which showed this to be an issue. I could find NONE. I know it is an issue on railway signal lines, but given the miles of cable to induce voltage on, that is reasonable. Some industrial applcations may also produce this effect. I suspected it may be just a marketing ploy for rare and specialised circumstances, such as demonstration boxes. After all, IF it really was a problem, then surely you would give some real world examples with figures to back it up? Subsequently I even asked some of the equipment manufacturers for real world examples. No replies with examples. Which tells me it is a scam.

[@olly7673]

Another great educational piece from Mr Watts, though it does make me think that me striving to be efficient with my 4kW solar PV and DC driver LED lighting may bite me on the bum when it comes to AC RCD safety in as much as it is a contradiction and my RCDs won't protect me now due to DC saturation.

[@olly7673]

I want to go to RCBO DB, is the DC saturation effect applicable to a RCBO type of setup?

[@SparkyNinja]

The challenge here is identifying or even quantifying values of potential leakage, and of that if any leakage is DC in nature. Its early days, but this is where things are going for RCD selection. For now manufacturers will give some examples of typical types of equipment, I recommend doing a google search for RCD types and a company like Doepke that do some good info on this.

[@gbelectricks]

Is it possible to measure dc current with the ac supply energised? I’m talking about practical on site methods rather than maybe using an oscilloscope???

[@joss867]

Yes. I'm sure there is a leakage dector that works in a similar way to a ct

[@bernardcharlesworth9860]

Really good video we really need a new design of RCD for DC and AC faults from my knowledge of electronics that would not be expensive

[@BP-td5gv]

Great video

[@lumpyfishgravy]

The old D-Lok technique.

[@normanhartill1424]

Not sure of the origin of DC leakage to earth is in an AC circuit, what the implications are, how AC leakage to earth interacts with DC leakage to earth, how to measure or detect DC leakage to earth in an AC circuit?

[@irfp460]

Switchmode power supplies introduce DC currents.

[@learninglounge]

Nice video Dave.

[@pcuser7129]

This video has caused a bit of a stir on the IETs wiring and regulations forum, with one engineer saying it's 'severely misleading'. See: communities.theiet.org/discussions/viewtopic/1037/26118

[@ChristianWagner888]

It’s an interesting demo, but lacking in some regards. The test is done with 50mA and 250mA DC current which is much higher than Type A RCDs are specified to handle. Can you repeat the test with Type A RCDs which are only specced to work up to 6(!)mA DC current and demonstrate that Type A RCDs would really be superior in a significant way? Can you repeat the test with Type AC RCDs and only 6mA DC current to check if the common AC RCDs are really significantly less responsive? Can you replicate a realistic fault condition caused by an electronic device that has actually prevented an RCD from tripping? A discussion on the engineering forum IET EngX indicates that the demo is this video is insufficient or irrelevant. Please consider the points I raised and make another video.

[@SparkyNinja]

Hi Christian, thanks for your message. This video was just to demonstrate the impact of DC on an AC RCD. The rig originated from the Rail sector where traction current can be imported into the public supply network at values significantly higher than 1 amp. I haven't explored the idea of creating a 6mA DC leakage device for the type A question. I will look into it.

[@charliechimples]

Great vid. Thanks. 🐵

[@JNET_Reloaded]

Why you wired earth to neutral?

[@megazeus7972]

Simulating a tncs supply?

[@lclear25]

Curiously similar to an older John Ward called 'Effects of DC on Type AC RCDs. Hmmmn

[@SparkyNinja]

It's exactly the same rig. These videos were made weeks apart.