By Heinrich Wienold
Many utilities and network operators are faced with the question of “if” and “when” to invest in smart metering, and which technology best suits their installation from a technical and cost perspective. Solutions available up to now have not proven to be cost effective. This situation offers players such as Europäischen Funk-Rundsteuerung GmbH (EFR) an opportunity to take an innovative approach that offers cost advantages.
Combining EFR’s proven longwave ripple control with an optional robust and cost effective power line communication system not only results in both low initial and operating costs, but even offers expanded functionality.
Solution for cost efective smart metering
Basic smart metering functions are covered by the longwave channel itself. It can be used to address electronic meters, for example, for rate management. It is also possible to transmit consumption and other information that can be displayed on a separate monitor, which is either hard wired to the meter or uses a wireless connection.
Even without a downstream channel, the display, meter and longwave channel by themselves comprise a closed system that enables smart metering to be implemented very cost effectively. In addition, it fulfills the requirements for a variable rate incentive system. Since the system is based on unidirectional communication, it meets even the strictest data protection requirements. Nevertheless, an optional downstream channel interface exists. This allows meter readings to be accessed, making it possible to obtain detailed data of the type that is currently typical in the sector where customers’ rates are fixed. An additional or alternative option is to prepare the meter data for display on customers’ PCs.
Ripple control adds value
An outstanding feature of the EFR system is that it offers not only smart metering functions, but also provides a means to lower reactive power demand and improve network stability in seconds via longwave radio ripple control. Integrating ripple control functions is becoming more and more important in view of the increasing injection of regenerative power into the grid. Because it responds extremely quickly, the EFR system can reduce the risk of blackouts.
Network load balancing can be supported by an incentive system consisting of load dependent rates that motivate customers to optimise their consumption behaviour. The EFR system is also suitable for integrating components other than electricity; for example, heat, natural gas and water, making it possible to establish a cross-sector metering and rate management system.
Inherent advanta ges of the radio transmision path
The specifications for a smart metering system capable of rate or load management, high speed, reliability, data encryption or other means to prevent eavesdropping plus a high uptime guarantee, cannot be met cost effectively using present powerline-based smart metering systems. That is why the EFR system relies on longwave radio and a separate downstream channel.
The upstream channel uses the broadcast capabilities of longwave radio transmission for:
- Load management. The switching takes only seconds and the transmitted commands reach many receivers simultaneously. Deferrable loads could include air conditioning systems, electric heaters, hot water heaters, etc.
- Fast acting and reliable reduction of power injected into the system or emergency shutdown of (small) power generating facilities such as wind farms when there is a risk of network overloads
- Switching the rate structure and transmitting information for incentive management
- Other customer and global services such as rate forecasting, weather data, storm warnings and much more.
The above tasks benefit from the typical characteristics of longwave radio transmission: Radio waves reach any number of terminal devices within their broadcast range and transmission costs are independent of the number of receivers. Longwave radio transmission works independently of the power grid and therefore does not cause interference, nor is it affected by network problems. EFR has used longwave radio ripple control for load, light and rate management for over fifteen years.
Longwave signals propagate as a ground and a space wave. Because the propagation range of the space wave varies strongly depending on the time of day and time of year, EFR’s system relies exclusively on the ground wave. Reception is normally excellent within a radius of 400 km from a transmitter, even in basements. EFR has currently reserved exclusive frequencies for its current three European transmitters and the system has adequate capacity for additional tasks.
The radio ripple control uses carrier frequencies ranging between about 130 and 150 kHz and frequency shift keying. So already today, it generates digital signals by raising and lowering the transmission frequency. The EFR system uses standard protocols and is multi-client capable because it uses appropriate addressing and address assignment. The addressing allows individual receivers (such as electronic meters) or entire groups of receivers to be addressed. EFR also transmits a time signal so that receivers with clock functions can synchronise.
Downstream channel response time not critical
The optional meter reading capability requires technologies that guarantee unambiguous identification of the meter and are able to transmit contents such as the meter reading and status of each meter to a metering management centre. Either the transmission is triggered by a central server or the meters independently transmit their data at prescribed times.
Response time for this data is not important. Because they are time stamped, delayed measured values or measured value series can arrive at the metering management centre without causing problems. The EFR system can be supplemented by an optional downstream channel. Here the main priority is reliability. A robust powerline communications system (RPLC) can be used for this purpose.
RPLC is used exclusively to transmit along the “last mile”. From there, the data is transmitted to the metering management centre via GPRS, ISDN, DSL or other means.
RPLC operates at low transmission levels and uses low bit rates. This makes the technology affordable and the low transmission levels avoid EMF problems. Repeaters are not required because the system is designed for high noise immunity along the route between the meter and the node (transformer).
In cases where it does not make technical or economic sense to use the powerline technology, a GSM/GPRS solution is available to connect the meter to the metering management centre. In this case, the technology used for mobile phone applications would be applied. Low rates can be offered because communication is limited to transmitting metering data and fault signals from the customer’s installation. The meter does not need to be reachable via the GSM/GPRS channel, because the radio ripple control is on standby in the upstream channel.
The ripple control and metering management centre
The key component of the EFR solution is a high availability IT environment, which handles the rate, load and injection management commands, as well as rapidly initiating transmissions and administering the metering data generated by the remote meter reading process. EFR’s central computer is used for this purpose. It is configured redundantly and is interfaced with established communication channels. It is easy to expand the system with optional functions such as weather warnings, or to customise energy data management (EDM). In contrast to established EDM solutions, the energy data management system can be designed to suit customers with fixed rates. Its main job is to gather metering data, check it for completeness and plausibility, then process and compress the information. The data is made available to or transmitted to utilities for billing purposes.
Other optional features are available; for example, internet services can be added, which are managed from the metering management centre, from where information is made available to customers on a password protected website. This could include consumption data in the form of tables, graphs or statistics; that is, information that provides additional customer benefits by way of an incentive system.
A power grid operating system geared toward stability will require sophisticated, fast acting load and power injection management. Encouraging fixed rate customers to shift their consumption peaks to periods of lower network demand will also contribute to load balancing. This can be accomplished by incorporating power consuming customers into an incentive system supported by variable rates. The EFR system takes the above approach and combines it with smart metering tasks and customer services such as weather forecasting. Radio ripple control and a robust power line communication system or GSM/GPRS meet the specifications for the upstream and downstream channels at a competitive price level.