The drivers behind the different AM activities in Europe reflect the different cultures in the European community. Whereas some AM activities are clearly driven by the vision of directive 739, other activities go far beyond the ‘classical AMR’ (automatic meter reading) applications. In some countries, centralised tariff and load management is well established. Many of these systems are based on ripple control technology, which is old enough to have reached the stage where renewal must be considered. Advanced metering systems offer a cost-effective alternative to reinvestment in ripple control. In addition, extended features (demand supervision and control, demandbased tariffs, consumption profiles and so on) offer new ways for tariffication and load management.
In liberalised energy markets, the regulators tend to drive distribution costs down to a minimum. On the other hand, the regulator must ensure that the distributor maintains a certain minimum quality of service. Advanced metering (power outages, under/over voltages etc.) provides the means to supervise the quality of supply and to optimise the investment in the distribution network.
Table 1 shows an overview of the most common AM applications in Europe.
Among the 25 European member states, two have made a clear decision towards large scale deployment of AM systems. Other countries – in particular those that have an outdated meter park which needs to be replaced anyway – are expected to follow soon.
THE ITALIAN CASE
Enel, the leading Italian electricity provider and network operator, decided in 2001 to integrate all its residential customers into an automatic meter management (AMM) system. By the end of 2005, 30 million households should be equipped with advanced meters connected via power line carrier (PLC) to Enel’s management system. Thanks to the new system, Enel is able to offer innovative tariffs while substantially reducing operational costs.
Acea, the independent energy distributor of Rome, has decided to follow the same path and has started the installation of its advanced metering system, based on PLC communication. By providing a customer terminal, Acea goes one step further towards improving the customer relationship.
Italy has a long tradition of maximum demand-based contracts for residential customers. Long before the introduction of AM, the meters were already equipped with a breaker, disconnecting the customer when he consumed more than the contracted power. By providing remote setting of maximum demand thresholds, the AM system substantially reduces the costs of the contract changing process.
THE SWEDISH CASE
Sweden is the only country in Europe that has transformed the idea of accurate monthly billing into a national law. By 2009, 5 million Swedish electricity customers must be billed monthly according to their actual consumption. This law triggered a huge market for AM systems. In contrast to Italy, the Swedish AM systems focus on ‘classical’ billing data acquisition. The basic functionality of the residential metering point typically consists of:
• A total energy register
• Two rate registers
• A downloadable rate switching table (TOU)
• A profile (over one year) of daily or monthly billing values.
Several options, such as hourly consumption values, quality of service indicators, and interfaces to gas, water and heat meters are expected to make the systems appropriate for future requirements.
Sweden is a huge country offering a large variety of distribution networks, from very rural networks with 1 to 5 customers per MV/LV transformer to urban networks with more than 1000 customers per LV network. An optimal AM communication infrastructure must be adapted to the network type. Today several communication systems operate successfully – low frequency PLC with signals crossing over the MV/LV transformer, low power radio networks, high frequency PLC systems with concentrators or gateways at the MV/LV transformer station, and systems using the public GPRS/GSM networks.
EUROPEAN UTILITIES ON THE THRESHOLD OF AM
Triggered by the activities in Italy and Sweden, AM has become a major topic for most European utilities. The economic and legal environment varies considerably in the different countries, but the business case can usually be narrowed down to two scenarios:
The monthly billing scenario, where a law requires monthly meter reading. In this case the installation of an AM system can be economically justified by the ‘classical’ meter reading application alone. All extended functions are just additional business opportunities.
The complex contracts and bad payers scenario, where the residential customers are used to demand-based contracts that may even include the possibility of a complete disconnection of the power supply; where further, substantial savings can be realised by reducing technical and nontechnical losses; or where load management is part of the contract.
In the latter case the economic justification is not always obvious. Detailed clarification of the critical issues is necessary prior to investing in full scale AM systems:
• Is the remote disconnection of customers legally feasible?
• What kind of security system is necessary to prevent the misuse of disconnecting customers?
• How can the liability of the utility be limited for consequential damages due to disconnection?
• Does the customer accept demand-based contracts which could lead to disconnection?
HOW IS EUROPE ADOPTING AM?
While Italy seems to have decided in favour of PLC, in Scandinavia several communication technologies are competing against each other. An overview of the major communication technologies used in Europe is presented in Figure 1.
PLC systems use carrier frequencies between 9 kHz and 95 KHz in the Cenelec A band1. Typically the frequencies are chosen well above 30 kHz. Due to the high carrier frequencies, communication is restricted to the low voltage (LV) network; i.e. the signals do not cross the MV/LV transformer. These PLC systems typically provide a channel capacity of 1000-3000 bits/sec. Besides many proprietary solutions, standardised PLC systems (IEC 61334-5-1) exist and are offered by several manufacturers.
A concentrator acts as a gateway between the LV-PLC network and the public telecom network (pure gateway solutions are also possible). The concentrator manages the PLC communication, performs scheduled or spontaneous data acquisition tasks and stores the results. Communication in the LV network is free of charge. The PLC communication network is available just for advanced metering applications. Mission critical communication tasks can be dispersed over time in order to achieve maximum reliability.
Engineering and Installation
PLC systems which are designed for plug and play installation (e.g. according to IEC 61334-4-512) do not need any engineering effort. The concentrator and the metering units are installed without any pre-configuration; in particular systems) and with the communication statistics provided by the concentrators, critical points are identified and countermeasures are planned. No pushbuttons must be pressed after installation. The system automatically detects new metering points, configures the network and optimises the message routing paths. Installation is normally performed by just one person.
In the case of modifications in the distribution network topology (e.g. repair work) the metering points are automatically handed over from one concentrator to another (a new transformer feeds the corresponding network part).
All data which is collected at the metering points and stored in the concentrator must be transported to the central data management system. If no wire-based medium is available at the concentrator, GPRS is the most cost-efficient communication channel. The data volume to be transported between the concentrator and the data management centre normally does not exceed the minimal volume included in the lowest priced GPRS contracts.
Radio systems use frequencies in licence-free bands or in bands which are reserved for utility applications. Some systems are hierarchically organised; some use meshed technologies. Radio systems are typically used in rural locations. Concentrators – similar to PLC – serve as gateways to the public telecom network. The radio systems are based on proprietary technologies; there is no IEC standard available.
Engineering and Installation
Prior to installation, radio systems need intensive engineering. Topology maps considering radio coverage must be computed, and locations for the repeaters and concentrators must be identified. The radio devices are typically equipped with external antennas. If the meter is installed in a metallic box, a hole must be drilled and the antenna attached at the outside of the box. The antenna must be directed for optimal transmission and reception. Normally the installation of a radio device needs two persons.
Communication quality in a radio network must be supervised. Topology changes (growing trees, new buildings) can substantially influence the communication performance. With the help of GIS (geographical information systems) and with the communication statistics provided by the concentrators, critical points are identified and countermeasures are planned.
These are similar to the PLC operating costs.
These systems offer direct wireless access to existing telecom networks and to the Internet. There is no need to establish and maintain a new communication infrastructure. The channel capacity required for advanced metering applications is negligible compared to typical business applications. Many GPRS providers assign only temporary Internet addresses to the meters. This could make additional GPRS routing functions necessary in the central data management system. Additional security measures must be considered for communication over the Internet. Finally, the system should not rely on GPRS only – the classical GSM data service should be kept available as a backup medium. Experience in Scandinavia shows that a close co-operation with the network operator is required for large-scale deployment of GPRS/GSM-based systems. Today the cost of a GPRS modem still exceeds the cost of a PLC modem by a factor of two or more.
ENGINEERING AND INSTALLATION
Prior to installation, GPRS systems need some engineering. Radio coverage of the different providers must be considered in the planning process. Contracts with suitable providers must be negotiated, and the SIM cards need to be configured accordingly.
Maintenance of the GPRS/GSM network is done by the network operator. As a consequence, the utility depends on the quality of service provided by the network operaor.
These are substantial for GPRS-based systems. It is the fixed cost per point which makes GPRS economically unsuitable for large-scale metering applications. The cost created by the data volume caused by a residential meter can be ignored. The total operating costs over a period of five years can easily exceed the equipment cost of a PLC communication module.
Table 2 summarises the different communication technologies and evaluates their suitability for major advanced metering applications. Considering the high engineering, installation and maintenance costs of radio systems, PLC systems are increasingly being considered even for rural areas. With the price of GPRS modems, GPRS becomes the alternative in a very rural environment. The economic threshold between PLC and GPRS depends on the operating fees charged by the operator. With today’s standard contracts, the threshold lies between 5 to 10 meters per LV network; in other words, PLC is the choice for LV networks with more than 10 customers, while GPRS is more economical for LV networks with less than 5 customers.
The first generations of AMR systems (radio or PLC) were based on manufacturer-specific solutions. With market globalisation, the utilities can no longer rely on local, proprietary solutions. Only a standardised system which is completely open and where no hidden property rights and licencing issues are involved can guarantee availability into the future. In addition to EdF in France, a major Scandinavian utility has begun the deployment of an AMR system based on international PLC standards (IEC 61334-5-1).
Standardisation began at the communication protocol level, but experience from industrial and commercial metering shows that a standardised protocol does not ensure interoperability on the data management level. Today major IT costs are caused by the incompatibilities of data models between different applications. The IEC 62056-62 standard provides the data models that support advanced metering applications.
In Scandinavia, some of the GPRS/GSM network operators have identified metering as a new business opportunity. They are offering monthly billing data collection, based on GPRS, as a service to utilities. Considering the fact that the current GPRS tariff structure is one of the major road blocks for the mass deployment of GPRS metering, these new service offerings could change the markets completely.
Metering technology normally stays in the field for 15 to 20 years, but communication technology will undergo radical changes during its lifetime. Only a meter able to upgrade to new communication media will be able to handle these changes. A strict modularisation between the metrological and the communication parts will allow the utility to exchange the communication module without re-approving the meter.
Low frequency PLC systems with signals crossing the MV/LV transformers are successfully used in rural areas of Scandinavia, where the installation of a concentrator cannot be economically justified. However, due to limited bandwidths the applications are also limited.