AMI in the city of Gí¶teborg


By Tomas Arnewid

A new law will come into effect on 1 July 2009 in Sweden. The law, the first of its kind in the world, states that all electricity customers in Sweden must be billed for actual usage and that the usage is presented per calendar month. This will in effect render manual reading obsolete and makes it necessary to install a system that can read the electricity meters remotely once a month. In Göteborg there are 275,000 meters for customers below 63 A, which must be replaced.

In 2004, when the new law was drafted, Göteborg Energi started looking at different alternative solutions for remote reading. At that time, the only solutions developed were based on either PLC (power line communications) or, to a smaller extent, radio on proprietary or restricted frequencies.

The investment cost for an undertaking such as this is quite substantial. Even though it is possible to drastically reduce the number of staff involved in manual reading, the return on investment is poor to say the least. Even if the simplest and cheapest solution were to be implemented, the return would be negative (Figure 1).


Figure 1 – Projected return on investment for AMR.
When investment cost, operational cost and possible
savings are all taken into account over a period of 18
years, the project return is negative

So it came down to a strategic choice: Either get the cheapest possible system in order to adhere to the new law, or find more savings and/or extra revenue to warrant a more advanced system. It is the view of the top management at Göteborg Energi that in order to reap the real benefits of remote reading one must in the future go from monthly readings to hourly readings. The shorter the time cycle between readings, the more useful is the information for the end user. Hourly readings give a very different understanding of usage pattern than monthly or yearly readings.

The more advanced metering systems of today have a much broader spectrum of possible services than those from only a few years ago. Hourly readings, on demand readings in real time, remote connect/disconnect, power failure alarm in real time, monitoring of power usage and voltage levels and other advanced functionalities are all now available. With these added functionalities in mind, Göteborg Energi decided to make the most of its investment and look for the most advanced system available at a reasonable cost.

In the spring of 2006 the Metering Project at Göteborg Energi was given the task of not only finding the best system available at a reasonable cost, but a supplier that was willing to take on the responsibility of installing 275,000 meters prior to July 2009 and also manage and operate the system for a minimum of four years after completed installation. During the summer of 2006 a tendering process was initiated.


Figure 2 – Göteborg Energi’s proposed AMI

Göteborg Energi must conform to the Law of Public Tendering, which dictates how a large tender process like this must be conducted. After an initial pre-qualification phase, nine out of 17 applicant suppliers were invited to submit a tender. During the fall of 2006 eight tenders were received. The solutions covered all available means of communication available on the market, as well as one new solution. Four suppliers supported PLC as the main form of communication, two had selected GPRS, one suggested radio on a restricted frequency, and one, the new entrant on the European market, had ZigBee as the main form of communication.

Internally in the project the focus prior to this had been very much on which form of communication was the best – the cheaper PLC or the more advanced GPRS. In the evaluation of the tenders, and in light of some of the problems the other utility companies had had with their chosen solutions, it became more and more clear that the key was really the central metering system at the heart of the different solutions.


Figure 3 – Example of functions of Aimir:
Active/reactive energy hourly profile

Some of the systems that were offered were very basic and some were not even developed and still only in the planning stage. One supplier offered Göteborg Energi the opportunity to become the first customer in their new system under development, but it was not the wish of the project to become a guinea pig in developing something from scratch.

A lot of time was spent in different groups evaluating the large amount of information contained in the tenders. Several of the tenders were delivered in large boxes due to their extent. Meetings were held with all the suppliers who presented their solutions in detail.

In the end it became very clear that one of the suppliers had a system that was beyond the others in functionality, user friendliness and advanced thinking. And the fact that the metering infrastructure was based on ZigBee as the main form of communication did not reduce the allure of the solution. In addition, implementing an infrastructure using ZigBee for electricity metering could be extended to gas, water, home security services, etc., sharing it with other utilities and service companies and thereby increasing revenue and compensating the negative ROI.

The system that was chosen was Aimir by Nuri Telecom of Korea. Their partner, High Tech Security of Norway, is the contractual partner and the company responsible for installing the meters and the infrastructure as well as operating the system for at least four, and possibly eight, years.

The infrastructure consists of 275,000 meters, which will communicate through ZigBee with approximately 11,000 concentrators. An additional 7,000 repeaters will enhance the reach of the concentrators where necessary. From the concentrators GPRS or optical fibre will be used to connect the concentrators to Aimir, the metering system. The single phase meters will be supplied by General Electric and the polyphase meters by Aidon, Kamstrup and Landis+Gyr (Figure 2).


Figure 4 – Aimir monthly chart of
daily profiles

Aimir is extremely powerful, with a large range of functions which will make it possible to get a very detailed view of the customer’s power usage and behaviour (Figure 3 – 5). Among other things it will be possible to see the quality of supply on several phases, detect theft, compare different customer or customer segments, get an overview of the topology of the net and a hundred other functions. In the upcoming system acceptance test more than 190 functions will be tested.

ZigBee communicates as an open standard in the USA on the 2,400-2,483.5 MHz and 902-928 MHz frequency band. For the globally open standard ZigBee uses the 2,400-2,483.5 MHz frequency band. The higher frequency of 2.4 GHz enables a data rate of up to 250 kbps instead of 40 kbps in the 902-928 MHz frequency band. The ZigBee network is built up as a self configuring mesh network. This means that if the signal can’t find its usual route, it will “jump” on other ZigBee modules to find another route to communicate. Thus the network becomes stronger the more ZigBee modules are installed and high reliability is coupled with flexible routing.

The reach of the ZigBee signal is often quoted as below 250 metres line of sight and applications discussed for ZigBee have up to now been focused on home automation. With the Aimir solution a reach of more than 2,000 metres line of sight has been attained, opening up ZigBee’s suitability for a totally different set of services and applications. The rather low bandwidth of course means that ZigBee is no substitute for WiFi and other broadband services (Figures 6). One of the main advantages of ZigBee is the low power consumption. The concentrators have a usage of only 3-4 W, not much more than that of an electrical meter. A battery operated ZigBee module, for example for water metering, will have a battery life exceeding five years.


Figure 5 – Aimir multi-site comparison

To date 200 meters and 4 concentrators have been installed as an on-site test installation. At the time of writing system acceptance testing (SAT) is under way. When the SAT has been approved, the next big milestone in the project is a “mini-rollout” planned for the winter of 2007/08.

Once the full rollout begins in the spring of 2008, 275,000 meters will be installed over a 15 month period. This means that approximately 90 electricians will install 1,000 meters per day, or 2 meters per minute. This will involve contacting 42,000 customers in order to book appointments to access their meters. Some areas, including a few islands, contain primarily summer homes and must be visited during the summer. A number of installations have restricted access for various reasons, such as military installations.

The logistic chain stretches from Korea to Sweden through China and Denmark. Concentrators and communication modules are manufactured in Korea by Nuri Telecom. The meters are manufactured in China, Greece and Denmark. Some installation and testing must be performed in Göteborg. And all must be in place in order that the installation teams always have the right equipment for the installation at hand.

An estimated 5 percent of the meters will not be possible to replace on the first visit. In some cases the surrounding electrical wiring is in such poor state that it has to be replaced before the meter replacement, while in other cases there are trees, bushes, wood piles or other obstacles in the way of installation.

Within Göteborg Energi the project organisation comprises approximately 15 full time people, coordinating all the tasks and acting as the recipient of the installation. On the supplier side, High Tech Security has a project organisation of approximately 20 to control the installation and all that has to be delivered in the form of radio planning, integrations, hardware, software, plans, documentation and supplier coordination – the main one being the company responsible for the physical installations, with roughly 100 persons involved full time.


Figure 6 – Comparison of technologies

Nuri Telecom is supplying experts on the system and ZigBee flown in from Korea. General Electric has staff involved in Germany as well as in the US. Kamstrup has involvement from both Sweden and Denmark. High Tech Security is based in Norway. So it is a truly international project taking place. The goal of the project is to finish installing the electrical meters and have all meters in operation by the .

The Nuri system was chosen based on the advanced functionality of Aimir, but what really makes the project and the future extra exciting is the ZigBee infrastructure that will be built. Aimir will make it possible to have a much more detailed view of the pattern of energy consumption of all the customers. It will be possible to obtain a very good overview of the low voltage network for planning and management, with real time alarms when power failure occurs. The quality of the electricity can be monitored, theft in the network can more easily be detected and when power peaks occur it will be possible to manage the demand. All power failures will be recorded, making it possible to reimburse customers.

All of this was behind the selection of the choice of supplier. But the part that really got Göteborg Energi buzzing is the new infrastructure that will make Göteborg the world’s first ZigBee City. There are mainly four areas where the infrastructure can be used:

  • Metering: Once the ZigBee infrastructure is in place, it becomes stronger the more meters are added due to the mesh structure. It is therefore only positive to add water, gas and/or district heating meters, as well as meters for everything else that might be interesting to meter
  • Monitoring: This can be water levels in the canals, temperatures on road surfaces, cars passing a certain point, or water quality in the ocean or lakes, to give a few examples
  • Alarms: This is potentially a big area including fire alarms, burglar alarms, personal alarms, alarm for leaks of various kinds to mention a few
  • Management and control: Street lights, control units in the district heating network, locks for homes and offices as well as customer applications in homes are all suitable for the ZigBee infrastructure.

The potential of the infrastructure is deemed so large that a new business unit is currently being formed in order to manage and market the potential services in the new infrastructure.

The various external services that are currently being looked at more closely are divided into three groups – energy-related services, communication-related opportunities and positioning services. Potential customers are the different business units within Göteborg Energi, private home owners, businesses, other municipalities and communal services and hospitals, as well as content providers who can use the infrastructure for their services.

It is of course essential that the infrastructure is largely installed before additional services can be offered on the market, and given the rollout plan, this is estimated to take place during the second half of 2009.