Gulf Island Off-Grid System - Part 4

mike95490 · September 2013

Re: Gulf Island Off-Grid System - Part 4

I think the smart meters use a ZigBee based radio scheme, and some simple encryption and checksums to prevent spoofing your bill.

But since it's a short range, mesh system, perhaps there is a central tower with a yagi antenna aimed at your meter.

David and Laura · September 2013

Re: Gulf Island Off-Grid System - Part 4

Re #58 - We don't have one yet, but the protocol is pretty simple, and there's hardware out there that allows access to the transmitted data.

http://www.howmuchsnow.com/arduino/gridinsight/

Re #59 - For the iTron meters, it broadcasts in the 900 MHz band (and interferes with the 33 cm ham band, no less!)

You have to identify your own meter, since it's pretty easy to pick up readings from neighbours meters. Fortunately, we don't have any nearby neighbours, and even if we did, they don't have power meters.

Re #60 - Nothing seems to be encrypted. The meter doesn't seem to receive data, just transmit it periodically. It may be able to receive data, but I don't have any information on what it would receive, or what (or if) there are any protections.

Re #62 - While some smart meters use ZigBee to provide home access to consumption data, the meters that are used by B.C. Hydro don't seem to use that technology.

When I get some time to actually hook things up for reading the meter data, I'll start another thread going into detail on what I had to do. Right now, we haven't even purchased any of the parts yet.

This would be a fun SDR project, too.

NorthGuy · September 2013

Re: Gulf Island Off-Grid System - Part 4

David & Laura wrote: »

Re #60 - Nothing seems to be encrypted. The meter doesn't seem to receive data, just transmit it periodically. It may be able to receive data, but I don't have any information on what it would receive, or what (or if) there are any protections.

Someone may cover his meter with tin foil, then setup a transmitter that is transmitting lower usage data. Surprisingly, noone throught about this.

niel · September 2013

Re: Gulf Island Off-Grid System - Part 4

won't work unless the foil is totally surrounding the meter and is grounded. signal leakage could occur for any and all wires in and out of the meter too.

inetdog · September 2013

Re: Gulf Island Off-Grid System - Part 4

niel wrote: »

won't work unless the foil is totally surrounding the meter and is grounded. signal leakage could occur for any and all wires in and out of the meter too.

I suspect that the communication is carrier current over the power wiring rather than airwaves anyway. Can anybody confirm or contradict that?

Most if not all use a mesh network in which each meter transmits for relay to the next meter that it can reach which is closer to the central collection point.

niel · September 2013

Re: Gulf Island Off-Grid System - Part 4

you could be right as i'm unfamiliar with how they go about it. they could couple to the ac lines to act as an antenna.

solar_dave · September 2013

Re: Gulf Island Off-Grid System - Part 4

inetdog wrote: »

I suspect that the communication is carrier current over the power wiring rather than airwaves anyway. Can anybody confirm or contradict that?

Most if not all use a mesh network in which each meter transmits for relay to the next meter that it can reach which is closer to the central collection point.

Here they are over airwaves.

From the APS site.

MYTH: Automated meters pose a safety risk to APS customers

FACT: Automated meters are safe. They use wireless technology to communicate information about electricity usage to APS. The meters transmit this information through radio frequency signals. Wireless smart meters result in much smaller levels of radio frequency than many existing common household electronic devices such as cell phones and microwave ovens. According to a study by the Electric Power Research Institute, a cell phone held against one's ear exposes someone to more than 1,000 times the radio frequency as an APS automated meter from a distance of 10 feet.

http://www.apsmeters.com/myth.php
http://apsmeters.com/pdfs/Automated-Meters-Myth-vs-Facts(1).pdf

I believe they are ZIGBEE but am unable to confirm that, I see the receivers on top of light poles in most every neighborhood.

David and Laura · September 2013

Re: Gulf Island Off-Grid System - Part 4

Re #64 - There are lots of security vulnerabilities with smart metering systems, but for most of them, you'll eventually get caught. That's how they are designed (It's a cost trade-off).

The key risk is that someone is able to modify the meter itself without triggering the tamper detection systems. There's been a couple of cases of that, but they usually involved insiders from the smart meter manufacturers.

Re #65 - Shielding is easy to detect and tricky to do right. Most attacks would just jam the legitimate signal during transmission, and then transmit a fake signal.

Re #66 - All of the meters that I have worked with and seen being deployed in North American smart meter rollouts are RF-based. Power line carrier doesn't scale well, and has quite a few technical challenges.

Our meters here in B.C. are 900 Mhz based (iTron)

Re #67 - The antenna is inside the meter. The coupling of low-power to high-power subsystems is expensive, so these two subsystems are kept completely isolated for cost and safety reasons.

Here's more details about these meters then most people would ever want to read, but it sure is interesting stuff:

http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001021126

David and Laura · September 2013

Re: Gulf Island Off-Grid System - Part 4

Note that B.C. Hydro claims that the data is encrypted:

[98] BC Hydro assigns each smart meter a unique digital certificate that it uses to verify the authenticity of the information sent from the meter to BC Hydro. BC Hydro also uses this certificate to facilitate secure communications between the meter and the systems located within BC Hydro. This method of information signing and encryption ensures that people from one household cannot decrypt or read data from another household’s meter. It also ensures that others cannot intercept and read the data during transmission from the meter to BC Hydro.

Source: Investigation Report F11-03

It also looks like our meters have Zigbee HAN support built-in:

https://docs.zigbee.org/zigbee-docs/dcn/11/docs-11-5774-00-0mwg-bc-hydro-rfi.pdf

It is interesting that device pairing will only be permitted if B.C. Hydro approves it, and enables the meter to do so.

David and Laura · September 2013

Re: Gulf Island Off-Grid System - Part 4

So, I did a little more digging — The meter we have has a different software load from the ones that B.C. Hydro is deploying to their customers. That may explain why ours sends out ERT messages in the clear.

So, what our meter does may not be representative of what B.C. Hydro's meters are doing.

inetdog · September 2013

Re: Gulf Island Off-Grid System - Part 4

David & Laura wrote: »

Note that B.C. Hydro claims that the data is encrypted:

[98] BC Hydro assigns each smart meter a unique digital certificate that it uses to verify the authenticity of the information sent from the meter to BC Hydro. BC Hydro also uses this certificate to facilitate secure communications between the meter and the systems located within BC Hydro. This method of information signing and encryption ensures that people from one household cannot decrypt or read data from another household’s meter. It also ensures that others cannot intercept and read the data during transmission from the meter to BC Hydro.

That description was actually rather well written from a technical viewpoint. It recognizes the difference between encryption and signing. In this case signing prevents someone who tries to send fake data from being able to produce an acceptable message.

From that description, though, it sounds like, unlike the normal HTTPS or SSL protocol, their message encryption is secured by the private key of the client rather than the central server. This makes sense for this application and in particular for a mesh network, but does mean that the client private key is used more extensively than desirable from a purely cryptographic point of view.

The saving grace is that the economic return from cracking the key pair for a single meter does not justify throwing a lot of computational resources at the problem.

In the US, the regulators and POCO do not seem to be as concerned about user data privacy. (Predictable)

David and Laura · September 2013

Re: Gulf Island Off-Grid System - Part 4

The final labelling is completed, and matches the original plans:

attachment.php?attachmentid=5917

Finally, the system is largely complete. Everything is working, and we have two weeks without any problems, with the meter reading 14 KW of power consumption.

We have also finished linking up the two systems, so we can run our cabin inverter off the main system, and use the cabin system as a power source to wheel power up to the main system.

Now it's time to write some monitoring software.

Attachment not found.

zoneblue · September 2013

Re: Gulf Island Off-Grid System - Part 4

It seems like you have an impressive configuration. Did you do the design and install, or did you get someone in?

Does the twin sunny boy, sunny island setup allow you flexibility to add more arrays into it easily? The system obviously cost quite a bit to setup, hence it seems to merit more pv. In contrast I know a guy who recently installed 10KW pv off grid with little more than a pair of fm80s, and a single outback inverter.

David and Laura · September 2013

Re: Gulf Island Off-Grid System - Part 4

Re #74 - We did the design work, which you can see on the initial thread. The design was verified and the install was done by a local solar company, and we helped out.

The SMA AC-Coupled system gives a lot of flexibility, in that the system can continue to run despite multiple failures, and is easily expandable. It can also be coupled together, which was helpful given that we now have two systems. We designed and built it out for more solar panels, but we want to see how we do with what we have initially. Tripling the solar would be pretty easy now (and would mostly help during the winter), and we could even use micro inverters. Of course, the mounting for the panels would cost more than the panels themselves.

A lot of the cost was because we didn't have time to do more work ourselves. Building the system to code, and building it so that it will be able to withstand a major earthquake also significantly increased the cost.

The panels and inverters are the smallest part of the cost — facilities work (container, foundation, cables, trenches, the solar rack, etc) was the largest expense, followed by the batteries.

Gulf Island Off-Grid System - Part 4

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