Design Article
Enabling next gen smart utility meters
Milen Stefanov, Texas Instruments Inc.
10/2/2012 11:24 AM EDT
1. European regulations for RF communications
The relevant norm for Sub-1GHz communications in Europe is the ETSI 300 220-1 V2.3.1 (February 2010). The established 868 and 433 MHz license-free ISM bands for metering applications were expanded with a 75kHz narrowband at 169.400MHz for meter reading applications. The maximum transmit power permitted is +500mW (equals +27dBm), the duty cycle is <=10%. The channel spacing is 50kHz or less; LBT (listen before talk) or AFA (adaptive frequency agility) channel access may be used, but both are not mandatory.
Obviously, having a +27dBm radiated power low-cost RF link at 169MHz will deliver a superior range coverage compared to the existing wM-Bus solutions with +25mW (equals +14dBm) at 868 MHz (see Figure 1). Note that “old” T-mode and the “new” C-mode each use two different frequencies, one for the meter-to-data-collector direction and a second one for the link from the data-collector to the meter.
Click on image to enlarge.
Data collectors in T-mode transmit at 868.3MHz with maximum +14dBm and in C-mode with up to +27dBm at 869.525MHz.
The range of RF metering solutions is the biggest problem to solve when deploying smart meters in dense populated areas in Europe with multi-storey buildings and unfriendly RF environments with multiple concrete and brick walls between the different RF nodes. This turned out to be the main shortcoming of Zigbee®-based 2.4GHz solutions in the UK, where the existing ZigBee SE1.1 products failed to deliver enough range in urban areas. A new generation of wM-Bus-enabled smart meters at 169MHz is aimed at solving the range issue in countries like Italy or France.
The longer range of the 169MHz RF link simplifies the system architecture and reducing the total cost of the networks by avoiding repeaters and eliminating the repeating functionality in meters. Less functionality means lower Flash and RAM size requirements for the metering nodes as well as shorter product development and certification due to the lower software complexity.
The relevant norm for Sub-1GHz communications in Europe is the ETSI 300 220-1 V2.3.1 (February 2010). The established 868 and 433 MHz license-free ISM bands for metering applications were expanded with a 75kHz narrowband at 169.400MHz for meter reading applications. The maximum transmit power permitted is +500mW (equals +27dBm), the duty cycle is <=10%. The channel spacing is 50kHz or less; LBT (listen before talk) or AFA (adaptive frequency agility) channel access may be used, but both are not mandatory.
Obviously, having a +27dBm radiated power low-cost RF link at 169MHz will deliver a superior range coverage compared to the existing wM-Bus solutions with +25mW (equals +14dBm) at 868 MHz (see Figure 1). Note that “old” T-mode and the “new” C-mode each use two different frequencies, one for the meter-to-data-collector direction and a second one for the link from the data-collector to the meter.
Click on image to enlarge.
Figure 1: WMBus modes S, T and C and ETSI 300220v2.3.1 relationship
Data collectors in T-mode transmit at 868.3MHz with maximum +14dBm and in C-mode with up to +27dBm at 869.525MHz.
The range of RF metering solutions is the biggest problem to solve when deploying smart meters in dense populated areas in Europe with multi-storey buildings and unfriendly RF environments with multiple concrete and brick walls between the different RF nodes. This turned out to be the main shortcoming of Zigbee®-based 2.4GHz solutions in the UK, where the existing ZigBee SE1.1 products failed to deliver enough range in urban areas. A new generation of wM-Bus-enabled smart meters at 169MHz is aimed at solving the range issue in countries like Italy or France.
The longer range of the 169MHz RF link simplifies the system architecture and reducing the total cost of the networks by avoiding repeaters and eliminating the repeating functionality in meters. Less functionality means lower Flash and RAM size requirements for the metering nodes as well as shorter product development and certification due to the lower software complexity.
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WKetel
10/3/2012 9:18 PM EDT
I see a whole lot of discussion about the technology for the communication with the smart meters but only a small amount about how this is going to save enough energy to be worth the effort. Of course, the very first use will be to raise prices a lot just when everybody wants power the most. We all know that is the primary goal of the two way system. The other goal is to eliminate the expense of manual meter reading, which will reduce the utilities costs quite a bit, but will not reduce our price for power at all.
The way to eliminate all of the privacy concerns is to keep the specific minute-by-minute consumption data in the meters, and to just totalize the product of KWH and the rate at the time of consumption. Then the utility could poll the meters to determine the charge for that month's power. No customer information except for the total charge would ever need to be sent out, just as in the past when meters were manually read. The utility has no need of individual household consumption at any particular time, only block by block, or subdivision by subdivision. The assertion that they need to know the individual rate of use at any particular instant is not valid.
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GPBobby
1/18/2013 11:06 PM EST
Data is only useful to the extent that it can alter some outcome, in this case, a customer's use of electricity. Almost no electrical customer even knows that their new smart meter is capable of turning off their power. The above article states, "to enable utilities to ease peak power demand..." where ease should be read as: a) a total disconnect; b) a rolling brown out; c) by interfacing with your own personal in home network to turn off selective appliances such as A/C, dryers, heat pumps or any other device which has built in communication capability.
I can see a small business in modifying newer appliances (if possible) to make sure they cannot communicate. The polite way to modify power consumption is to let the consumer know (by checking an Internet site at their convenience) their current charge per kWh. Then let them decide what devices to turn off.
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pekon_
1/24/2013 11:42 PM EST
But if this was so lucrative, then why did google retired their power-meter service ?
http://www.google.com/powermeter/about/
Its just that there isn't enough eco-system built around to manage|optimize energy. And also its usage is expensive.
Many companies have smart-metering products from long, but lack of government urgency, and tough norms are also pulling this market low.
[pekon]
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GermanInTI
2/27/2013 4:46 PM EST
Not only MCU but also memory is a key factor for smart utility meters. TI is somehow leading the MCU part but not the memory, suprisingly even having a great technology called FRAM in Texas. FRAM makes the meter design extremely simple and flexible. Fujitsu and Ramtron leads the memory market for smart meters with FRAM. TI wake up...
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