Generator Recall

powerstream · Veteran Member

RE: Generator Recall

dorian · Guru

Here is a 2-minute design for a 5mA leakage sensing circuit that has a trigger voltage of around 43V. There would be 41V across the resistor, plus about 2V across the primary winding of the toroid. I don't know whether this complies with the relevant standards, but it wouldn't be difficult to modify the design if need be.

                                  frame/earth
                                     ~40VAC
                                       |
                                       |                     toroin
  Active o--- 5mA leakage impedance ---o--- 8K2 resistor --- )()()( ---o Neutral
                                                             ======
                                                             )()()(
                                                             |    |
                                                             |    |
                                                             o    o
                                                            solonoid

-- Edited by dorian on Sunday 9th of February 2014 07:03:41 PM

brian · Guru

I just had a look at one of Safelec's u-tube videos.

The short one on class 1 and class 2 appliances, link below.

You may have to copy and paste the link.

www.youtube.com/watch?v=eZMji8V9XNk

Have a look at it and tell me what you think of his last statement about use in wet areas.

brian · Guru

dorian wrote:
Here is a 2-minute design for a 5mA leakage sensing circuit that has a trigger voltage of around 43V. There would be 41V across the resistor, plus about 2V across the primary winding of the toroid. I don't know whether this complies with the relevant standards, but it wouldn't be difficult to modify the design if need be.
                                  frame/earth
                                     ~40VAC
                                       |
                                       |                     toroin
  Active o--- 5mA leakage impedance ---o--- 8K2 resistor --- )()()( ---o Neutral
                                                             ======
                                                             )()()(
                                                             |    |
                                                             |    |
                                                             o    o
                                                            solonoid
 
-- Edited by dorian on Sunday 9th of February 2014 07:03:41 PM

Maybe you should go into competition against Safelec...You already have the (sic) toroin and solonoid spelling down pat. wink

dorian · Guru

Brian, if a generator has an E-N bond, then the RVD will be sensing 0V. Therefore it will be useless. That has been my point all along. Previously you have lectured me as to the mandatory requirements for an E-N bond in conjunction with an RCD (because an RCD cannot function without it), yet now you seem to be suggesting that this requirement is either unnecessary, or will lapse in future. I'm confused.

As for your implication that an open neutral presents a hazard in a generator/inverter application, could you please elaborate? AISI, an open neutral on the load side (where you have previously indicated) will simply result in zero power output without exposing the user to any safety risk. This is completely different to an open service neutral at or before the entry point to a domestic or commercial premises.

http://electricalnotes.wordpress.com/2012/07/28/impact-of-floating-neutral-in-power-distribution/
http://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/DangerofOpenServiceNeutral~20020816.htm

As for how the RVD would detect an open service neutral, I would like that to be explained. AFAICS, the only way (if an E-N strap is in place) would be to monitor the active potential and ensure that it remains within an allowable range. The Safelec web site makes no mention of this.

On the question of standards, Safelec says ...

There is no specific standard that is available for the RVD/RCBO device because of the dual method of fault detection. In the absence of such a specific standard the device has been tested and compliant with those sections which are appropriate with normal RCD standards. This is Australian Standards AS/NZ 3190 and AS/NZ 3100, exceeding the requirements of safety installations as specified in AS/NZS 3000.

In other words, "there is no standard for RVDs, so we used the one for RCDs". BTW, I'm not making a judgment, I'm just stating the facts. Morever, doesn't this imply that the requirement for an E-N strap is still in place?

As for the claimed secrecy of the invention, here is the original patent (Feb 12, 2004):

http://www.google.com/patents/WO2004013943A1?cl=en
http://www.patentfetcher.com/GetPatentPDF.php?f=Pubs/WO/20/04/WO2004013943.pdf

Can I expect a hit squad now?

When I visited the Safelec web site, my first impression was of an electrickle injuneer who had difficulty with electrical jargon ending in "oid". It now appears that the designer is in fact an electrician who appeared on the ABC New Inventors program on May 4, 2005.

http://www.abc.net.au/tv/newinventors/txt/s1356442.htm

My initial impression at that time was one of suspicion. He was very secretive, and provided almost no information that was of a technical nature. However, it is clear from the patent document that he is a lot more capable than the average electrician.

After the ABC program, he gave some minor insight into the device in this "open debate about electrical safety":

http://www2b.abc.net.au/guestbookcentral/list.asp?numtoview=&GuestbookID=171&start=&sort=&filter1=&filter1val=&filter2=&filter2val=&filter3=&filter3val=&view=&advanced=&Action=&pagestart=98

He confirms that the Protex device "References off the Neutral" and "does not use power until a fault is detected".

brian · Guru

You're probably right Dorian, these things can't possibly work, and I can't explain it in any more detail, so I'll leave it at that.

I have never intended to lecture you on any subject, so please accept my apology if that is what I have done.

My intention was only ever to pass on what knowledge that I could, and which I believed to be correct.

I was not intending to imply or otherwise say that an open neutral on a generator presented a hazard. You will note that I also said "coupled with a poor earth" in the same sentence, which would apply to a grid connect rather than to a portable generator installation which would have no earth. Perhaps I could have been clearer in my meaning.

powerstream · Veteran Member

Why should you apologise Brian you are entitled to say what you think is right and Dorian has taken old information to conclude what he has.
The patent he refers to definitely would not work with a generator or Inverter and was subsequently redesigned.
A second patent was lodged and the old firm did not check it and the patent was lodged with the same drawings as the first instead of the new drawings and subsequently became subject to prior art.
Due to the control of the old firm wanting something better the RVD was made redundant fiscal year end 2009 and was sold.
Before that second patent became redundant the new persons that pursued the problem had a new third patent application lodged specifically to cover generators and inverters with corrected drawings and details.
To-morrow I am led to believe that a further video should be uploaded which defines the RVD use with an isolated transformer supply this then can be applied to both the generator and inverter lines as well.
Ian

brian · Guru

I'm not apologising for what I have said Ian, just for the unintended vein with which it has been received.

I have just read their mining industry paper, and I must say that it is a whole lot of waffle with very little substance.

One would hope that their personal presentations were more enlightening than that.

dorian · Guru

Brian, in that other thread you and Peter corrected a misconception that I had regarding the inherent safety of an isolated generator. Rather than being annoyed at the "lecture", I'm actually thankful for your explanation. In fact the example you cited could be used to demonstrate how an RVD without an E-N strap could give rise to a safety hazard.

Imagine if a one appliance had an E-N short. This would render the RVD ineffective. Now imagine that you were standing on the mass of earth and that you were in contact with a second appliance which had an active leak, or, to use your example, imagine that you were to stick a knife into a toaster. Your body would now be exposed to a potential difference of 240V. In the absence of an E-N strap, there would be no current imbalance in the RCD, so it would never trip.

In short, an RVD with an E-N strap would be useless, while an RVD without an E-N strap would be dangerous. AFAICS, an RVD in a generator amounts to snake oil.

BTW, I'm still digesting the videos, white paper, and patent.

powerstream · Veteran Member

Brian
Your reference to wet areas that you made from viewing one video of Class one and 2 appliances may be answered by watching the two other videos of how an RCD works and How an RVD works and in a modern house where is your earth path with plastic and fibreglass baths and plastic water pipes and drainage pipes.
Dorian
The isolated power video should be up this morning and as soon as I have the link I will post it as it is done with an isolation transformer which would then relate to both inverters and generators.
Also hopefully to-day another video on reverse polarity should be up so I hope both you and Brian review the videos and comment as this needs to be sorted and I really appreciate the interaction.
Ian

-- Edited by powerstream on Tuesday 11th of February 2014 10:00:23 AM

dorian · Guru

I'm having trouble understanding some of the claims made by Safelec. For example, there is this one:

When a voltage above a predetermined level of 43V is detected, the RVD is triggered, causing a 30mA imbalance being placed across the RCD/RCBO thus isolating the protected circuit in under 20mSec, this is called "Rapid Isolation".

IIUC, the RVD section detects a voltage fault and then responds to this condition by creating a 30mA current fault in the RCD section. The RCD then operates the breaker. How can this "tandem" action be faster than an RCD on its own?

BTW, the solenoid in my trivial circuit could be made to operate a set of contacts that would shunt the RCD's test button. This would achieve the abovementioned outcome.

My second question is in regard to the claimed isolation current of "8mA constant" (or is it 5mA, as in the block diagram?). I can't see how that would be possible, given that there would be times when the RVD would be inoperative and the device would instead be relying on its RCD. Is this figure the rating of the RVD section on its own, and does the RCD section have the typical 30mA rating? If so, then isn't this specification misleading?

oldtrack123 · Guru

Hi Dorian
re [quote}Imagine if a one appliance had an E-N short. This would render the RVD ineffective. Now imagine that you were standing on the mass of earth and that you were in contact with a second appliance which had an active leak, or, to use your example, imagine that you were to stick a knife into a toaster. Your body would now be exposed to a potential difference of 240V. In the absence of an E-N strap, there would be no current imbalance in the RCD, so it would never trip.

In short, an RVD with an E-N strap would be useless, while an RVD without an E-N strap would be dangerous. AFAICS, an RVD in a generator amounts to snake oil.

BTW, I'm still digesting the videos, white paper, and patent.[end quote]

The whole point of the RVD is that unlike a RCD, where the EN bond MUST be before the RCD,]The RVD senses that first fault ANYWHERE IN THE SYSTEM.
That fault that changes the isolated supply to an earth neutral supply ,but not neccessarily MEN
It can either trip a loadwithin it's capacity or an attached RCD
There are various models to cover the various earthing systems !! from fully isolated, floating, EN, MEN .
Some are polarised!

PeterQ

powerstream · Veteran Member

The isolated transformer video has been uploaded to google to-night and will be loaded on the website in the morning it runs for 6 minutes please bear with it for now.

Ian

dorian · Guru

Thanks Peter. I was under the impression that one model fits all. Anyway, I had already written the following before I saw your reply.

This device is giving me a headache. The block diagram refers to active and neutral, so this would imply that it works in a bonded generator and in a domestic situation where there is a neutral-earth bond.

However, the Safelec web site is somewhat ambiguous. It is not clear whether the generator must be an unbonded type in order for the RVD to work, or if it can have an E-N strap.

http://www.safelec.com.au/applications.html

A generator is an ideal application for the RVD as it allows its full potential to be realised when used as an unbonded generator. The RVD enables detection of the 'non-dangerous 1st fault condition', if either L1 or L2 should develope a fault to frame the RVD creates an imbalance accross the RCD, causing isolation. This reduces the risk of a person becoming part of the electrical circuit and exposed to an electric shock.

An RVD protected generator enables multiple pieces of class 1 hand-tools/equipment to be used from a sole power source. Monitoring the frame for a voltage rise, the RVD complements the RCD operation. This allows for a high convenience factor to be realised as no earth staking or other preparatory work is required, resulting in a 'plug and play' outcome.

The statement that "if either L1 or L2 should develope (sic) a fault to frame the RVD creates an imbalance accross (sic) the RCD" would suggest that the presence of an E-N bond would be sensed as a fault condition by the RVD (but not the RCD). If that is the case, then how does it work in a domestic premises?

AISI, in order for the device to detect a leak between frame and either of L1 or L2, it must allow leakage current to pass through it and return via the opposite supply terminal. The following trivial circuit would achieve this end.

              diode                    diode
 L1 (live) o---|<|--- 5K1 ---+--- 5K1---|>|---o L2 (live)
                             |
                             |              frame
                             |---)()()(-------o----/\/\/---> to either L1 or L2 (load)
                          toroid ======           leakage
                                 )()()(          resistance
                                 |    |
                                 |    |
                                solenoid

A leakage current of 8mA from L1 or L2 would develop approximately 40V at the sense terminal of the RVD with respect to L2 and L1, respectively.

-- Edited by dorian on Wednesday 12th of February 2014 08:14:41 AM

powerstream · Veteran Member

Quote:A generator is an ideal application for the RVD as it allows its full potential to be realised when used as an un-bonded generator.
I do not see what is hard to understand and or what is ambiguous about the above.

A utility company has indicated it would be ideal for potential use in rural power applications .

In urban domestic situations it has to be used through an isolation transformer that is why the video that is going up on the website to-day should help.

Ian

-- Edited by powerstream on Wednesday 12th of February 2014 09:01:33 AM

-- Edited by powerstream on Wednesday 12th of February 2014 09:02:37 AM

powerstream · Veteran Member

www.safelec.com.au/safelec-videos.html

The isolation video is now on the website.
Ian

dorian · Guru

The block diagram refers to active and neutral. These terms are only applicable to bonded installations. An unbonded installation has no active or neutral. That's where the ambiguity arises.

FYI, here is the same original patent at the USPTO:

http://patentimages.storage.googleapis.com/pdfs/US7378761.pdf

-- Edited by dorian on Wednesday 12th of February 2014 06:01:46 PM

powerstream · Veteran Member

Dorian
So what is your point you criticised the product, you assumed you knew what it was , you called it trivial , you called it dangerous and all you can come up with ambiguity that you say is doing your head in and that is after you tried to reinvent it in five minutes.
The product has been test proven in laboratories, and approved by the regulator.
What is doing your head in is that you cannot conclude that you are correct in a few days that has taken years of research and testing to come to fruition.
Ian

gold dandelion · Senior Member

**** I hope schapelle comes on soon.