CoServ Electric s RF Mesh Advanced Metering Infrastructure. RF/EMF Investigation

Transcription

1 CoServ Electric s RF Mesh Advanced Metering Infrastructure RF/EMF Investigation Date Analysis Performed: 05/03/2012

2 Introduction CoServ Electric is a not-for-profit electric distribution cooperative and, as such, is regulated and directed by its Board of Directors (elected representatives who oversee the operations of the cooperative). These Directors hold a fiduciary responsibility to represent the interests of the Member - our consumers. Surveys show that these Member consumers (made up of residents and business owners across Collin, Denton, Tarrant, Grayson, Wise, and Cooke counties) are tech savvy, and look to CoServ to provide them with resources to save energy and money. In order to meet our Members expectations, our company must innovate and empower our Members with advanced technology to manage energy use. After significant research and an extensive application process, CoServ Electric s Board approved a $17.2 million Department of Energy Smart Grid Investment Grant in March 2010 to support the installation of the AMI project an electric distribution technology initiative called the CoServ ecogrid. In September 2010, CoServ announced its selection of Landis+Gyr s Gridstream RF technology to provide the advanced metering and distribution technology supporting the initiative. The system consists of a robust two-way communications network (a wireless system supported by collectors and routers), advanced metering, distribution automation and personal energy management applications. Once fully deployed, the system will provide operational efficiencies that will reduce costs, streamline operations, improve system reliability, and offer Members new technology to monitor and reduce energy usage in their homes and businesses. CoServ has begun work on full system deployment, with project completion scheduled for April In that timeframe, all CoServ Members will have an advanced meter installed on, or at, their premise. Radio Frequencies Radio Frequency (RF) is produced by all transmitting devices which are common and in widespread use today. Examples of RF producers include radio broadcast stations, television stations, satellites transmitting services to earth, and even our sun. A normal consequence of RF is the production of an electromagnetic field or EMF. There are three factors for consideration of human exposure to RF 1 : 1. Signal Strength 2. Distance from the transmitting device 3. How often the device transmits 1 An Investigation of Radiofrequency Fields Associated with the Itron Smart Meter, EPRI Technical Report , December 2010, page 3.

3 Establishment of Safe Exposure Levels The Federal Communications Commission (FCC) provides the regulatory standards associated with exposure to RF/EMF. IEEE standard C (ANSI/IEEE C ) specifies safe levels of human exposure to radio frequency electromagnetic fields. The FCC has adopted the IEEE standard as the foundation for regulations related to human exposure limits and has been presented as a regulation in 47CFR The source document for human EMF exposure limits is now known as Office of Engineering & Technology (OET) Bulletin 65. There have been no changes to the exposure limits. OET Bulletin 65 refers to two safety limits which are Occupational/controlled limits and General population/uncontrolled limits. General population/uncontrolled limits will apply to situations which the general public may be exposed, but not fully aware of, their potential exposure or cannot exercise any control over their exposure. An example of this is a radio transmission tower which is exposing people to EMFs. This definition is the basis for comparisons of regulatory exposure limits to actual field readings taken by CoServ personnel. This is the category CoServ s AMI RF Mesh network, including the AMI meter, falls under. OET Bulletin 65 defines the limits for Maximum Permissible Exposure as values of electric and magnetic field strength and power density for transmitters. For equipment that operates intermittently or in a burst mode such as the AMI meter- OET Bulletin 65 defines the period over which exposure can be averaged and will represent a similar level of exposure as a maximum continuous exposure. This data produces a minimum safe distance to the source. The devices on a Member s residence or business that uses the RF Mesh network are the radio module inside of the meter and the devices used for a Home Area Network (HAN). Table 1 2 below provides the equivalent minimum safe distance in an uncontrolled environment for the mentioned RF sources. RF Mesh Device Residential and C&I modules Home Area Network Radio Home Area Network Device Table 1 Equivalent MSD Uncontrolled Environment 0.63 inches 0.05 inches 0.05 inches As a worse case, this table indicates a person will need to remain 0.63 inches from the radio device in an AMI meter for an exposure limit to be greater than allowed. The distance between the radio and the glass covering the meter is greater than this; so a hazardous exposure is not possible if the normal mode and construction of the system and meter remain intact. Another measurement to be considered with a RF/EMF investigation is the power density of the transmitting device. For this investigation, the RF Mesh devices remain the same. Table 2 3 provides information related to power density in milliwatts per square centimeter (mw/cm 2 ). 2 Landis + Gyr, Acceptable Exposure Limits to Gridstream RF Devices, page 6. 3 Ibid.

4 RF Mesh Device Max FCC Permissible Exposure F[MHz]/ foot from source (Continuous Transmission) Percent of FCC Exposure Limit Exposure at 1 meter (3.28 feet) from source Continuous Transmission) Percent of FCC Exposure Limit Residential and C&I Endpoints % % HAN Endpoint HAN Radio % % Table 2 Review of this information shows that, under normal exposure conditions, the exposure level for the RF Mesh equipment, including the meter, will be below FCC requirements.

5 Field Analysis Date Analysis Performed: 05/03/2012 Readings Performed by: Kevin Maynard Communications Foreman, CoServ Electric Device Used: NARDA SRM-3006 Serial Number: H-0024 Calibration Date: 03/27/2012 The device used to test EMF is a NARDA SRM-3006 Selective Radiation Meter. It is used to measure RF and EMF levels and is equipped with a spectrum analyzer. The device allows for the determination of EMF and RF strength levels by providing ambient and specific frequencies down to individual components for detailed analysis. The device allows for ability to calculate the maximum permissible exposure for a given frequency. It is equipped with a three axis (iso-tropic) E-field antenna which is a non-directional electrical field measurement antenna. The SRM-3006 captures the signal(s) from the AMI meter and will display in real time the actual pulse of the transmitter and the maximum peak of the transmit packet from the AMI meter. The SRM-3006 samples RF signals in the MHz spectrum for approximately 5000 to 6000 cycles with a sweep time of 39 milliseconds at each distance. This cycle duration is adequate to capture transmissions from the AMI meter as it communicates to the RF Mesh network. The SRM-3006 is programmed to show the FCC General Public Access regulatory limit which is displayed as mw/cm 2, mw/m 2, and as a percentage of the FCC limit. Additional programming of the SRM-3006 includes the limits of several other standards and regulatory rules. The frequencies used by the radio module and the HAN device were not investigated as separate frequencies. Therefore, captured power densities will be accumulative of the devices and conclusions will be based on a worst case scenario. Actions Using the SRM-3006, outdoor readings were taken at one (1) foot and three (3) feet distances from the meter for 5 minutes at each distance. Readings were also taken inside of residence at approximately two (2) feet directly behind the meter. Once all of the readings had been completed inside of residence, another reading was taken inside the residence to capture all ambient frequencies which existed in the residence. Readings Location: Outside, 1 foot from meter

6 Figure 1 - Power Density Findings: Reading is at mw/m 2. Conversion to mw/cm 2 divide by 10,000 = mw/cm 2. Figure 2 - FCC Exposure Percentage Findings: Reading is 4.497% of FCC Exposure percentage. Location: Outside, 3 foot from meter

7 Figure 3 - Power Density Findings: Reading is at µw/cm 2. Conversion to mw/cm 2 divide by 10 = mw/cm 2. Figure 4 - FCC Exposure Percentage Findings: Reading is.202% of FCC Exposure percentage. Location: Inside, 2 feet from meter

8 Figure 5 - Power Density Findings: Reading is at mw/m 2. Conversion to mw/cm 2 divide by 10,000 = mw/cm 2. Figure 6 - FCC Exposure Percentage Findings: Reading is.035% of FCC Exposure percentage. Location: Inside Ambient frequencies

9 Findings: No remarkable findings Comments Members may be able to find a relatively inexpensive meter that claims it provides EMF readings. These meters are typically a wide band product which covers a frequency range of 1MHz to 8GHz and are equipped with a simple omni-directional antenna. It should be noted, these devices are not designed to be frequency specific or a true EMF measurement. These meters will measure fields from all sources that transmit from 1MHz to 8GHz and typically do not measure using E-Field or H-Field. E-

10 Field is the electrical component and the H-Field is the magnetic component of an EMF field. Conclusions Comparison of FCC Guidelines to the manufacturer s meter specification and the field investigation is shown in the table below. Location/Distance FCC Permissible Power Density (mw/cm 2 ) Manufacturer Spec Power Density (mw/cm 2 ) Calculated Percentage Power Density Measured (mw/cm 2 ) Calculated Percentage to FCC Recorded Percentage to FCC Outside/1 foot % % % Outside/3 foot % % % Inside/2 foot % % % The RF/EMF emissions from the installed AMI meter at this residence falls well under the requirements of the FCC as defined in OET Bulletin 65. Additionally, the values recorded were under the specifications provided by the vendor of the equipment. An examination of the ambient frequencies in the residence show there are exposures which are naturally occurring and greater in power density than what is contributed by the AMI meter. For more information on AMI and the RF impacts, please refer to EPRI Radio-Frequency Exposure Levels from Smart Meters: A Case Study of One Model CoServ.com FAQ