With the implementation of communication technology for electrical meters underway in many other countries, there are still many unanswered questions surrounding the best implementation for India. There are, however, many incentives for implementing such a system that could make a significant impact on today’s metering challenges.
From the early days of the Ferraris wheel electromechanical energy meter, electrical metering utilities in India sought features that were less common in other regions of the world. Driven by a high occurrence of meter tampering, these features continue to be important as technology develops. With the implementation of communication technology for electrical meters underway in many other countries, there are still many unanswered questions surrounding the best implementation for India. There are, however, many incentives for implementing such a system that could make a significant impact on today’s metering challenges.
In the earliest electronic energy meters, energy could be stolen by reconfiguring the inputs to create an earth fault, redirecting the current to earth ground instead of the neutral wire. The introduction of the AD7751 (later renamed the ADE7751), the first fault tolerant electronic energy meter, by Analog Devices in the late 1990s sparked the rapid deployment of these ICs into stepper motor meters. Tampering could now be detected and prevented by simultaneously monitoring both the phase and the neutral current and billing the customer based on the largest reading. The integration of tamper detection changed the market by influencing utilities in India to incorporate such features into the tender requirements. It also became a way for utilities to improve efficiency and for meter manufacturers to differentiate their designs. The subsequent development of the ADE7761 brought a new feature to tamper protection, incorporating missing neutral detection. This allowed measurement to
continue based on the rms current reading when the neutral was disconnected from the power meter. Tampering continued to be a concern, as electromechanical meters were particularly susceptible to tampering using simple magnets. Before the deployment of electronic energy meters, aggregate technical & commercial (AT&C) losses of the electric utilities were as high as 38%. Low metering efficiency, tampering and pilferage were the main source of commercial loss for utilities. Over a period of ten years, many electricity utilities have successfully lowered their AT&C losses bringing the national average to 28%. This strongly suggests that combined with other improvements, advanced energy metering features have had a successful monetary impact. Throughout the development of the electronic energy meter, India has stood out as a feature rich, cost driven market where producing a meter that meets the advanced specifications at the lowest cost is essential for success.
The need for feature rich, tamper proof meters at very low cost has driven the single-phase metering market to widely adopt the system-on-chip (SoC) solution, which has rapidly become more popular than a two-chip solution using an analog front end (AFE) with a separate microcontroller. SoC technology combines the metering metrology with a low cost microcontroller and peripherals into a single package, thus reducing the overall cost of the meter. The SoC has met mixed success in other regions of the world that have been reluctant to move away from the more flexible two-chip solution.
Key features for today’s market include on-chip flash and RAM. A full range of energy measurements, including
active, reactive and apparent energy, available on both phase and neutral current inputs, is required to detect and prevent tamper attacks. An integrated LCD driver and full RTC create a complete system, reducing the number of external devices required. The inclusion of an external battery input and switchover circuitry ensures that the system operates in the absence of line voltage. A suitable solution that fills these requirements is the ADE51xx by Analog Devices.
In 2011 (and beyond), there’ll not only be more demand for these products, but demand for further advancement in almost every area of our lives including the vehicles we drive, devices we use, and energy we consume. Critical to meeting this demand, even if it is not always visible to the end users, is a culture of innovation that will drive thriving companies to match the insatiable appetite of their customers for new solutions and applications.
In addition to lowering the cost of the overall meter design, using an SoC has simplified the design process for meter manufacturers, as only a single IC has to be considered. This reduces the complexity of the board layout, as the performance of multiple ICs and the interactions between them are no longer issues for the meter manufacturer. Transitioning to the SoC has provided financial and ease-of-use benefits for the India meter market. The capabilities of these meters far exceed active energy billing and include features such as instantaneous current and voltage monitoring that could provide useful information on the grid. Deploying meters with such features helps ensure future-proof designs.
The Future in Communication
The long-term financial rewards of implementing an automated meter reading (AMR) network have provided sufficient incentives for many countries to commence wide-scale deployments of such technology. A significant portion of these savings arise from the removal of operating expenses, or man- hours, required to manually read every meter. Due to the lower cost of labor in India, these savings are not as considerable as in other countries. The immediate financial reward obtained from providing electronic energy meters to every household in India is far greater. The heavily subsidized, unmetered energy supply that exists in the agricultural industry, coupled with the large number of unmetered distri butiontrans formers, provides a significant potential market that is yet to be utilized. Village electrification as of July 2010 is close to 84%1 , yet again expanding the potential market for deployment of electronic energy meters. The advantage of integrated communication does not end at reduced labor costs, however. Automatic meter reading also has the potential to tackle the issue of meter tampering.
AMR allows more frequent meter reads, thus providing more data to the utility. This data can be used to monitor patterns in energy consumption and highlight any sudden reduction that could be attributed to tampering. A two-way communication system would facilitate the implementation a remote-shutoff feature, allowing the utility to immediately disconnect customers who have not paid their bills or have been caught tampering with their meters. Along with detecting tampering, this feature could act as a deterrent for such crimes. AMR also removes access issues that arise because many meters are mounted inside homes or apartments. Reading these meters presents privacy issues for customers and can limit the efficiency of the utility employee when access is not readily available. By removing the human error element in the meter reading, mistakes can be reduced and the overall efficiency of the system improved. The unquestionable potential for efficiency improvements makes a strong case for the implementation of integrated communication.
Metering architecture for Complex Communications
When communication is added to a metering system it can significantly increase the memory requirements of the associated microcontroller. As discussed, India has widely adopted the SoC solution that incorporates an integrated microcontroller and flash memory. As the level of communications complexity increases, this solution becomes limited, as integrating the microcontroller restricts the available flash memory and controller options. In countries that adopt communications, a trend toward reinstating the two-chip solution using an AFE and a separate microcontroller is developing as this configuration allows the metering portion of the system to become modular. A much larger microcontroller can perform all of the processing, including the communication protocols. A high-performance, three-channel AFE, such as the ADE7953 by Analog Devices can provide all the information to perform flexible anti- tamper algorithms along with a full range of metering measurements. As communications for the metering industry develop, a two-chip solution eliminates the need to redesign the metering module when the microcontroller requires upgrading. As the microcontroller increases in capability, this partition allows meter manufactures to achieve a lower cost by choosing the exact microcontroller that matches their needs. It will also reduce the cost and effort of upgrades, as many microcontroller families provide pin-compatible parts with a range of memory sizes. RF vs. PLC Two dominant technologies in metering communication market are Radio Frequency (RF) and power line carrier (PLC). Analog Devices offers solutions in both of these areas, with the ADF7xxx family of short-range transceivers for RF and the Blackfin processor-based Powercomm family addressing the PLC segment. Adoption of RF and PLC for AMR and AMI solutions has varied from one country to the next. PLC has become the strongest contender in many regions, including China, where it is believed that concrete buildings provide a challenge for many RF technologies. The dense population distribution lends itself to PLC technology as many residences are serviced by a single transformer, minimizing the number of concentrators hence reducing the overall cost. To date, there has been no mass development of PLC technology in India. A contributing factor may be the frequent power outages on the line, which disrupt PLC communication. When disturbances occur on the power line, the average time for restoration is over 70 minutes. These events pose a significant problem in India where the frequency and duration of these disturbances cost India an estimated Rs 43,000 crore each year2 .
RF communication, which does not rely on a stable line voltage, can function in the absence of line power, and is emerging as the strongest player. Providing a technology that can operate solely from battery power is key in India, where frequent periods of power failure can occur on the grid. The low-power nature of RF technology allows it to fit this requirement and be portable to both water and gas applications where low power is a key feature.
In 2008, regulators in India designated a UHF RFID spectrum. This spectrum falls between 865 MHz and 867 MHz, bringing it in line with other worldwide bands used for AMR, such as 868 MHz in Europe and 915 MHz in the US. The adoption of this band provides a regulated frequency spectrum that offers long communication range at low power consumption. Range and building penetration are major challenges for the originally considered 2.4- GHz architectures. Analog Devices’ ADF7023 high performance low power ISM band transceiver is well suited for AMR application in the Indian band. It features high sensitivity and excellent blocking specifications. The metering infrastructure is most often limited by interferers rather than noise. While sensitivity and performance to transmitter mask regulations at maximum power are critical performance metrics, adjacent/alternate blocking resilience is important as well. The large scale potential of RF metering networks makes the adjacent channel blocking amplitude more critical than the sensitivity specification as high interference rates caused by neighboring channels can disrupt communications and degrade efficiency. The ADF7023 by Analog Devices offers an industry- leading adjacent channel blocking specification of 38 dB at 200kHz offset over a 100kHz bandwidth.
Short Range RF Applications
The deployment of RF technology lends itself to apartment blocks where a single communications meter could be used to collect and store energy data from individual apartments in the building. This implementation provides immediate benefits to both consumers and utilities by removing privacy concerns and increasing the efficiency of reading the meters.
Such an implementation would not rely on the established mains network and, due to the dense population distribution, would significantly reduce meter reading overhead. Introducing automatic meter reading at a building level will allow the benefits of established technology to be capitalized improved and expanded. Condensing the number of meters that have to be read to one per building will simplify the next step of implementing a full communication system back to the utility.
While the above mentioned scheme works well for an apartment complex, the same could be extended to the electricity poles for facilitating AMR from individual households. Deploying the electronic energy meter with an RF based data concentrator on the pole leaves only the display electronics and RF transceiver to be installed at individual households. This approach eliminates the need for additional tampering features in electricity meters and facilitates AMR function without adding considerable cost to the implementation phase of this scheme.
The utility metering industry in India has developed to provide a large range of features that tackle the issue of tampering. Today, the dominant solution for single-phase metering is the SoC due to cost pressures. The implementation of an AMR metering system has the potential to increase reading efficiencies and tackle the issue of tampering. A suitable communication for India is RF technology, as communication can continue in presence of line disturbances. The developing etering infrastructure in India presents an opportunity to use innovative technology such as that offered by Analog Devices to provide immediate benefits to both the consumer and the utility.
1. Data obtain from the Ministry of Power, Government of India.
2. According to a joint study in 2008-2009 by Emerson Network Power, a business of Emerson (NYE:EMR) and the Manufacturers’ Association for Information Technology (MAIT), the apex body representing the IR hardware industry in India.