New technologies in the electricity industry – in particular automatic meter reading (AMR)– have revolutionised utilities, which today are able to read the meters of domestic customers remotely and thus get a better idea of customer consumption; prepare statistics regarding both technical and nontechnical losses; and offer new and faster services such as automated electronic bills. These advantages of AMR have been the key point for the start of ‘the new age of metering’.

At present, there are several methods that utilities can use to read their customers’ meters. Some are based on traditional reading methods, and can therefore be optimised using new technologies. For example, the human factor causes errors when readings are done manually, and customers prefer not to have strangers visiting their property. Customers also dislike estimated readings, which are often not accurate and result in a customer paying more than he needs.

The evolution of the metering market from electromechanical to electronic meters has created a new way to read energy consumption. This new way is called AMR, and the most well-known communication technologies are via modem, GSM, radio and PLC (power line carrier).

GSM or modem communications are expensive solutions for collecting the small amount of information contained in the meter. Radio systems are economic enough, but in some cases there are coverage problems. Thus PLC is a very interesting alternative for AMR.

NEW BUSINESS ALTERNATIVES FOR UTILITIES

New benefits have been opened to utilities since they have been able to use PLC as a communication system between the energy metering equipment and the billing system. Some examples are that losses can be studied in more depth, and that tampering can be easily detected (for example, being able to identify zero consumption over a long period).

In addition, a safe prepayment system is available. The energy is purchased in a convenient manner (at supermarkets, by phone, over the Internet and so on) and is loaded to the remote meter using the PLC system. Other applications include remote customer connect/disconnect, getting other data like voltage or power factor, studying the load profile of certain customers, and tariff flexibility.

When we started to talk about AMR some years ago, we began by trying to identify the best way to read the energy registers from the meters. What is the meaning of ‘the best way’? At the time, we thought it was the technology that could give us an economical reason for using the electric network, or the solution that allowed us to reduce the cost of reading. But now the question is, is that enough? Clearly the answer is no. We have new arguments that justify the introduction of AMR.

We know that we compete not only against our competitors but also against the traditional methods of reading, which are normally low cost. This means that the cost of PLC communication should be about the same as the traditional methods – the extra functionalities of an AMR system are enough to justify a slight increase in cost. So our goal is that the cost of the PLC technology has to be similar to other cheap AMR systems, but with more reliability, effectiveness and features.

This new concept for AMR is an alternative to the typical ‘point to point’ concept. The communication routes can be changed at any time, depending on the status of the mains network. In this new model the intelligence will be distributed in the network and not focused on the concentrator. It gives every meter the function of repeater of the frame, allowing the distance between the concentrator and the last meter to be increased. The system itself is able to choose the best way to reach a specific meter, using the information supplied by the other meters.

The communication between a meter and the concentrator can be interrupted in the event of noise or impedances, and this can lead to transmission errors. Distance is not always the greatest problem – in some situations, the greater problem will be variations of the characteristics of the mains.

Network PLC

The system’s repeater functionality can reduce or even avoid these problems, since each meter can determine if the communication signals should be retransmitted, processed or ignored. In this way, communication between the concentrator and a meter located a considerable distance away is possible if there is another meter between them, even if the meters are connected to a network experiencing noise or impedance problems.

Another important requirement is to have an easyto-use plug and play system. Manual installation of an intelligent network can be very complex, and the likelihood of errors can be high. The installation process should ideally be automatic, so that when a meter is installed the concentrator recognises it automatically, without intervention by the installer, and can start the meter reading process.

A high degree of security can be ensured using an encrypt mechanism to guarantee the integrity and the authenticity of all the data and to control access to the network, reducing the risk of manipulation by unauthorised users and external devices.

Once the data from every meter has been sent to the data concentrator, it must be delivered to the utility’s central data collection unit. There are various technologies available – Ethernet, USB and RS-232 are the basic interfaces, and there is also optical fibre, GSM/GPRS, WAN or similar. The decision as to which communication technology to use is one that will be taken together with the utility using the system.