TWACS smart meters problematic to public health and safety
The TWACS smart meters communicate with the utility by adding low frequency signals to the electrical lines. Some utilities promote such power line carrier (PLC) systems as a positive alternative to wireless smart meters. The reality is that all PLC technologies are problematic, including the “pulsing” TWACS systems.
The basic facts are that the TWACS system
• creates powerful dirty electricity
• the dirty electricity is a constant presence, possibly 24/7
• the dirty electricity turns all wires throughout the house into antennas
• keeping an analog meter will not help much
• the signals cannot be blocked or filtered
• scientific studies link dirty electricity with various health effects
- some people are sensitive to dirty electricity
- TWACS lacks basic security features
This article covers all these issues in detail.
Keywords: TWACS, DCSI, power line communication, power line carrier, PLC, dirty electricity, health, smart meter, security
The TWACS system
TWACS stands for Two-Way Automatic Communication System. It allows the utility company to communicate with smart meters placed on buildings throughout their service area. Some TWACS equipment is marketed under the DCSI name.
The communication system is two-way, which means the utility can both send instructions to the meter and receive data coming back.
The system can be used to read the electrical usage for a building, instead of sending out a meter reader once a month. The information is typically transmitted a few times a day, but could be only once a month. The transmission may contain information on how much power is used each hour of the day, or even every 15 minutes.
Other uses of the TWACS system are to detect power outages, faulty meters, voltage problems, etc. These functionalities will require transmissions throughout the day.
The TWACS system can also be used to remotely control utility equipment such as capacitor banks (Volt and Var Control).
Another possible use is to disconnect the electricity to a household remotely, instead of a service technician having to manually do that on site (using the Disconnect Switch Interbase).
The TWACS system may also be used for more advanced smart grid functions, such as turning off appliances in people’s homes during energy shortages or when the cost of electricity is high. This requires the installation of the Aclara Demand Response Unit or Aclara Load Control Transponder.
The TWACS system transmits using the existing power lines in an area. It usually does not use wireless transmissions to communicate, though it always radiates unintentionally (see later).
The power lines are used to transmit locally between each household and the TWACS receiver at the substation. From the substation, the system communicates with the utility’s central computer using other methods, such as fixed landlines, cell phone modems, microwave links, etc.
TWACS can communicate over dozens of miles. It is mostly used in rural areas and small towns where houses are further apart than in a city. Rural areas are more difficult to serve with wireless meters due to the limited range of some models.
For detailed technical information on TWACS, see the U.S. Patent Office web site(1) and other technical publications.(2, 3)
Identifying a TWACS smart meter
The TWACS system is marketed by Aclara in the United States, which produces modules that are installed inside meters from other vendors. The TWACS module is available for the FOCUS meter from Landis+Gyr, the I-210+ meter from General Electric, and other models as well. Some older mechanical (“analog”) meters have a TWACS transmitter installed. These are probably not used for new installations.
Smart meters with a TWACS transmitter may have a special label with the Aclara logo on it. It is usually placed on the front, but could be elsewhere. The Aclara logo is a red square with rounded corners and two crossed white lines.
TWACS-compatible equipment is also marketed by Itron/Schlumberger and Landis+Gyr under the DCSI name. These may be identified by a label with the equipment model, such as “DCSI-EMT-3F” or similar.
Other power line communication
There are other systems that communicate via the power lines. These are also problematic, but are not covered in this article.
Any type of system that communicates by transmitting signals via power lines is called a Power Line Carrier or Power Line Communication (PLC) system.
TWACS meters may also be wireless
Some TWACS meters also have built-in wireless transmitters. These are mostly used to get meter readings from gas and water meters on the house. The electrical meter then passes that information on, using the TWACS system. The Aclara Badger ORION product is such a system.
On more advanced systems, the TWACS meter may use wireless to transmit signals to a display screen or “smart” appliances inside the house.
The line pulses
A TWACS meter sends out a brief pulse about 60 times a second when it transmits. This pulse travels along the power line to the substation, where it is received. The voltage fluctuations from the pulse may also go in other directions on the local grid, including into other houses in the area, even houses several miles away.
The utility equipment at the substation also transmits by sending pulses on the grid, which it uses to send instructions to the smart meters. These pulses travel on all the local power lines and into all houses. The system would not work if the pulses did not travel to all houses. The pulse does not “know” which meter it is going to, just as the signal from a radio station does not know in advance where the radio receivers are.
For a detailed discussion of how the TWACS signals travel on the local grid, see appendix D.
A constant stream of pulses
A TWACS meter will take about eight seconds(4) to transmit its reading and status, which it may do once a day, every hour, or once a month. In between, it may transmit briefer “all is well” messages or other information. Most of the time, each individual meter does not transmit.
The TWACS controller at the local substation transmits much more frequently, usually several times a minute. It needs to transmit a signal every time a meter is to be read or checked up on, by prompting the specific meter to respond (master-slave polling). Some TWACS systems also allow the central controller to download information or programming to the meters.
Together, there is a fairly constant stream of signals on the wires. The signals will be coming from either the smart meter on the building, other smart meters in the area or the controller at the local substation. With future smart grid technologies, the traffic may increase dramatically.
The substation controller is likely to be the main source of pulses entering the household.
See Appendix B for more detailed discussion of how often the TWACS system transmits.
The TWACS pulses need to travel for many miles, sometimes dozens of miles. At the other end, the pulse signals must be clearly detectable above the regular line noise, so the pulses must be fairly powerful. The strength of the TWACS transmitters are not disclosed by the vendor, however.
Dirty electricity from TWACS
The pulses are more than just a simple pulse. They contain and cause a broad range of frequencies, which are all sent along the wires. The basic TWACS frequencies are in the 400 to 600 hertz(11) range and are jagged and irregular, unlike the smooth sinusoidal curve of regular power (50 or 60 hertz). These are called transients.
Depending on the physical layout of the local electrical grid, there will also be a wide range of harmonics generated from the basic pulse/transients, as they resonate across the wiring system. The upper harmonic frequencies may reach into the lower kilohertz range.
This is all referred to as transients and harmonics. A more descriptive term is dirty electricity.
Dirty electricity from other sources
Dirty electricity is created by other sources than the TWACS signals. Many types of household electronics can create them as well, though they tend not to be as powerful. The TWACS signals must be stronger than most other kinds of dirty electricity, to be “heard” above the other noisemakers on the line.
The power supply inside digital utility meters is a common source of dirty electricity. There are utility meters available with quality components that do not create much dirty electricity, but many meters use components that produce much unnecessary dirty electricity.
Avoiding the high frequency dirty electricity from the internal electronics in a TWACS meter is a reason to opt-out and use a mechanical meter instead, even though it may not help much with the dirty electricity from the low frequency TWACS signals.
The wires become antennas
When the broad spectrum of frequencies of the dirty electricity travels along the electrical wires, they are turned into antennas that radiate these frequencies. More precisely, it causes the electrical and magnetic fields around the wires to fluctuate (see Appendix C for details).
The wiring in buildings and along the roads will act like giant antennas, similar to what is used for some types of radio transmitters. Decades ago, this principle was used in the Soviet Union to bring AM radio to remote villages. The villagers used ordinary AM radio receivers to play the signals radiated from the power lines going through the area. The TWACS signals cannot be picked up by AM radios, as different frequencies are used.
Almost all wireless communication uses frequencies much higher than that emitted from the TWACS system. But some communication systems use frequencies in the same area.
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