240V Mains Project

[wigman27]

Hi all,

I know this probably isn't the best place for this type of question, however, I really would like the best opportunity for experienced feedback on this I can get and I feel this lounge is the best place for that.

My question lies around a new project a friend and I are working on at the moment that will eventually be on kick starter, its a power monitor for use in the everyday home. It will measure RMS voltage and current, apparent, reactive and real power, power factor and frequency. It will then log the information using the opensource EMONCMS. My idea at this stage is to have a self contained unit in the main switchboard that plugs into a power point to both power the unit and measure voltage. I am steering away from a 5v version using a plug pack as they can be so inaccurate, a 10% error at 5v is bearable, however, a 10% error at 240v is NOT.

The question is, how do I ensure its safety by design? I have had a good look through the Australian standards and Workcover requirements and it appears that it does not fall under the category that requires approval, however, must meet safety standards (obviously). My only plans at this stage are to sell them through a kickstarter campaign once it has been thoroughly tested. I hope to send one of the prototypes to Dave for his comment.

Can those in the know please provide some guidance on the things I need to consider, no matter how trivial you think they may be, ie, what isolation requirements are there? What input protection is required for safety if any? Are there any other international (to Australia) standards I would need to consider?

I am looking at creating a three phase version also, however, an "electrician free" installation is proving difficult to come up with! I will work on it!

Thanks in advance!

Lee

[Rerouter]

without a license your not meant to even pull forward your switchboard to get at the phases, much less wire in something to allow it to measure the voltage,

The other issue you face is no (or very close to no) switchboards have an outlet, nor an outlet within a meter from it, in fact most 20+ year old houses have them outside the house

all this probably explains what we see in the approaches taken by the products that are out there, with a current clamp unit that transmits wireless back to the base station in the house with the display,

The outside unit measures and calculates the RMS current, and with all the measurement points you can determine where the peak and zero cross should be (a crappy waveform could invert briefly when the voltage crosses zero), you timestamps it, broadcast it to the inside unit and it compares it with the voltage its measuring off its supply, as even being on the other side of the house you wont add any significant phase shift to the waveform,

if you sample fast enough you could even report the harmonic content of the line

using this current and voltage you have a working product that only has the umming and arring about fitting a battery powered box with a current clamp at your meter box,

[GeoffS]

Take a look at http://openenergymonitor.org/emon/  if you haven't already.

Their approach is to use clip-on current transformers for current measurement and a plug pack transformer for voltage.
All open source.

 I was going to install a small system to monitor the various tariffs I have. A licensed electrician has to install the current transformers  in the meter box and I found an electrician who would do so provided the local energy authority was OK with this but gave up trying to get the concept across to them.
.

[HackedFridgeMagnet]

Sorry to say but if you don't know the answers to these questions then I don't think it will be worth your time and effort.

Here is what someone has done.
http://saturnsouth.com/pages/products.php

Here are some that may apply

AS 60950

+ a list that someone sent me once

Electricity (Consumer Safety) Act

ERAC Electrical Equipment Safety System (EESS)

AS/NZS 3820:2009 ? Essential safety requirements for electrical equipment (+Amdt 1)

AS/NZS 3100:2009 ? Approval and test specification ? General requirements for electrical equipment

(+Amdt 1 & 2)

AS/NZS 4268:2008 Radio equipment and systems ? Short range devices ? Limits and methods of

measurement

Certificate of Conformity for Australia and New Zealand (DC plug pack)

[turbo!]

Use a PT and CTs with proper approvals already in place. Do all the tinkering on the secondary side.  Wall warts are very popular in the US as it avoids significant amounts of UL testing hassle by using off the shelf UL approved warts.

[calzap]

Hard to see how this project can be done on a shoestring budget if it's going to be installed in a service entrance panel.   The approvals and certification process would be expensive in the US, Canada or EU, and I would guess in Australia too.   Even inductive sensors on the wires leading into the service entrance panel would probably require approvals and certification.  In most jurisdictions, the wires going into service entrance panels have to be in a conduit.  So to install inductive sensors, the wires would have to be disconnected and pulled back, the conduit would have to be cut, an approved box installed for the sensors, then everything reconnected.

Many smart service entrance meters display voltage and current draw and have data output, usually IR or wireless.  Not sure the average residential or small commercial power user would be that interested in power factor.  For point-of-use measurements, there are a number of products on the market.  I like the Kill-A-Watt EZ made by P3.  It gives voltage, amps, watts, frequency, and power factor, but doesn't have data output connections.  I've done limited testing of voltage, frequency and amperage on it with my bench instruments, and it appears to be accurate.  Not sure if it's available outside the US, but similar products are.  They're powered from the 120 or 240 VAC input.

So to do whole premises monitoring, approvals, certification and installation would be expensive.  Point-of-use monitors already exist, but there may be an opportunity to develop the later with data output capabilities.

Mike in California

[wigman27]

Take a look at http://openenergymonitor.org/emon/  if you haven't already.

Hi again :-)

Thanks everyone for your comments! Yes I sure have seen that EMON stuff and its really nice!

I think I have decided to try and build this unit into a DIN rail setup in a similar enclosure to Circuit Breakers with external jack for CTs. There are too many issues with the single user installation version. Way too much room for the user to not install it safely.

As there are so many single phase versions out there I am going to put my efforts into a three phase version as there aren't too many of those!

I have received a few chips from Cirrus Logic which appear to be very good! So yes, I have done a fair bit of research on what's required for approvals and it doesn't need to be specifically approved but I will be sending it in to be inspected any way once its built!

Thanks again

Lee