The 59 meter dash – automatic rapid meter reading in Ronneby21 February 1999
The deregulation of both telecommunications and energy markets has opened a number of opportunities for utilities. A project at Ronneby in Sweden is being used as a test bed for a number of technologies.
There have been numerous recent technological developments that enable the power lines to be used to transmit data and information. These technical advances are summarised under the name Power Line Telecommunications (PLT). Although PLT is new and requires further advances, both in terms of technical capability and commercial equipment cost reductions, it has already demonstrated that the present, relatively limited data-transfer speeds are already sufficient for many useful innovative applications. A number of useful services are already feasible with data transmission in the kbps range, while current PLT speeds are about 1 Mbps. Speeds of up to 100 Mbps are predicted within a few years.
The potential advantages that are offered by integration of PLT and other information and communication technologies is massive. Examples include security from a distance, agent-enabled personal comfort services, intelligent energy and equipment cost-saving services, other forms of 'smart' home automation, and many others. All of these may easily be bundled through PLT with more conventional telecom and energy offerings.
Since the deregulation of the Swedish electricity market, many companies have attempted to bring 'added value' to their product. One of these could be various IT services, such as smart houses and load management, enabling utilities to both reduce customers' energy costs, and increase their comfort. The communication necessary for this would take place mainly on the electricity grid. This has already been tested out on a small scale. One such test has taken place in Ronneby, in southern Sweden.
It is expected that future electricity markets will probably focus on relatively short electricity delivery contracts. This will enable distributors to buy from one or two main suppliers and to purchase on the power exchange market.
With the dependence of Norway on hydropower, and the Swedish decision to phase out nuclear power, the Nordic electricity market is likely to be very strongly influenced by the weather. As a result, studies have shown that most distributors believe it will be imperative that tight control is maintained over load management.
Enersearch, a joint venture between Sydkraft and IBM Utility, is directing a large R&D programme called ISES (Information Society Energy Systems). Other sponsors of ISES include ABB Network Partner, EDF, PreussenElektra, IT Blekinge and Ronneby Municipality. As part of the project, Sydkraft and the University of Linköping are carrying out a number of different trials on the Ronneby energy system, including DSM, the use of the power line for remote meter reading, the use of intelligent agents and an evaluation of the economics of various investments.
The Ronneby project
Ronneby is 550 km south of Stockholm. The utility supplies 250 GWh of electricity, and 33 GWh of district heating a year. The expected maximum demand is 54 MWe and 10 MWt.
The Ronneby energy system was analysed in some detail, to see what effect the different tests had both individually and in combination. Initial estimates are that it is possible, through load management and efficiency improvements, to reduce the costs of supplying the town with electricity and heat by approximately 2.9 per cent.
The Ronneby trials use a PLT system called Integrated Distribution Automation and Management (IDAM), developed by Sydkraft and IBM. This was installed in the Påtrop region of the town of Ronneby. IDAM was used to read power meters in the region. The area consists of 59 households, ie, 59 different communication channels.
Loads connected to the LV grid interfere with the communication in several ways. As a result, the first element of the test was to find out how this interference affected the grid.
The LV grid in Påtorp has the following data:10/0.4 kV oil transformer, nominal 376 kVA, short circuit power 500 kVA; 6 LV cables secured with 225A fuses; One 10 kV cable; 21 cable boxes are distributed on the LV cables. The customers are connected to 18 of these cable boxes; Each customer connection is secured with 63A fuse.
IDAM was developed to provide a communication system for remote meter reading, and consists of three parts: the Multi Function Node (MFN), the Concentrator and Communication Node (CCN), and the Operation and Management System (OMS).
A MFN was installed at every household to collect data from the meter, as a separate or integrated part of the meter. It handles collection of meter values, and transmits these to the CCN. This transfer is initiated by the CCN. It is also possible for the MFN to spontaneously send messages to initiate specific actions, such as alarms. In both cases, the communication is only between the CCN and the MFN.
To prevent loss of data when the communication is not working, each MFN has a 40 day memory.
A CCN is used to collect data from and manage the MFNs. The CCN is installed in a transformer station, and in addition to communicating with its MFNs, it can control sensors and monitor the transformer station in which it is located.
Polling is the technique that is used to collect meter data from the MFNs. The CCN initiates a data transfer with each MFN every hour, asking for the current meter reading. The CCN notices if the communication fails, and, if it does so, it tries again later. The low voltage cables between the 59 MFNs and the CCN are used as transmission lines.
The CCN interfaces with the OMS server.
The OMS server manages the network of CCNs, and in addition to this, it also indirectly manages the MFN network. It collects the measured values and stores them for later retrieval.
The CCN is located in the transformer station T159. T159 is linked with an OMS server by means of an optic fibre. The OMS server and control room is located 1 km away, in a house called Villa Wega, which is also being used as a test site for home automation. The house uses an IDAM system for load control of some of its power consuming systems.
Normal IDAM operation
Analysis of the data indicated that on average, one in six readings had to be retransmitted. This requires a large level of retransmission in order to ensure collection of all meter readings, which in turn, requires the system to retain spare transmission capacity. In the test in question, there was plenty of available reserve transmission capacity.
Operation with harmonic injection
It is well known that the injection of harmonic current into the utility grid can cause problems. These problems could include additional heating and possible overvoltages in the distribution and transmission equipment, errors in metering and malfunction of utility relays, interference and interruption of communications signals.
A harmonic voltage disturbance was injected into the line in order to enable the response of the line to such interference to be determined. When this was done, the error rate rose to 40 per cent. This was an unacceptably high level, and work is still needed to resolve this issue.
Because of the unpredictable behaviour of the power line due to the hostile communication environment it presents, it will be hard to implement a system with a low error probability. A high error probability has to be anticipated.
Benefits of PLT
The tests in Ronneby indicated that there are a number of benefits to be derived from distribution automation. The conclusions were based on the following assumptions:That the average duration of power line interruptions could be reduced to 1-2 minutes per year per customer with the power grid fully automated. A complete district automation system would require automatic switchgear in every transformer station. Expenses for communication equipment are negligible in comparison with the expenses for switchgear. A complete district automation system would result in a substantial reduction in the service expenses used on the power grid.
The first implication of these assumptions is that district automation would be expensive to implement, but provides a more reliable service. Therefore, it is necessary to develop new businesses to cover some of the expenses of installing the automatic switchgear.
Around the world, remote metering has become the first main application for PLT. Deregulation of the energy market has created a need for remote metering of a large number of meters. Short intervals (up to one hour) between reading the meters was a driving factor for developing an automated system.
There are several questions affecting the implementation of remote metering, for example:What impact does deregulation have on the metering market? Will demand profiles be required for the large domestic market? Is such information protected and limited to the distributor? What is the return on the investment?
The results of the tests at Ronneby indicate that remote meter reading will result in expenses related to billing being reduced. This saving has been estimated to be of the order of 30 ecu per customer per year.
Another income source is rents from other utility companies, renting data transmission capacities for remote meter reading of other types of meters, such as gas or water.
There is also the potential for using remote meter reading to increase the profit through liberal power trade. In a deregulated market, each customer has a certain value to the utility. Regular analysis of the use of power by the various customers enables the utility to accurately evaluate the value of each customer.
The DSM part of the Ronneby project used the linear computer programming model MODEST (Model for the Optimisation of Dynamic Energy Systems with Time dependent components and boundary conditions). MODEST is a PDC model (Production, Distribution, Customers), which means that it covers most activities in the energy system. The model analyses the energy system as a collection of nodes and branches, with the nodes representing various different items of equipment (such as a boiler), and the branches representing energy flow. This enables the programme to evaluate the effectiveness of changes to the system (such as repairing or replacing specific items), and balance these against the cost of implementing the change in question. As a result, the cost-effectiveness of the changes, especially when related to greater speed of information flow between customer and utility, can be determined.
Input data for the model includes fuel prices, plant capacities and efficiencies, running and maintenance costs, demand profiles for electricity and heat, and investment costs. This enables the system to be optimised.
The DSM measures that were applied in Ronneby were load management and efficiency improvements.
The potential investments considered were:7 per cent efficiency improvement in industrial sector; 10 per cent efficiency improvement in residential sector; 5 per cent efficiency improvement in service sector; Maximum load management 4 MWe in industrial sector; Maximum load management 5.6 MWe in residential sector; Maximum load management 1.5 MWe in service sector.
At the current price levels for electricity, load management can reduce the system costs by roughly 3 per cent of the total system costs.
Because IDAM has been installed in Ronneby, the project had the opportunity to test how the introduction of intelligent buildings will affect operations. Sydkraft developed the 'Homebots' technology to do this, with the specific intention of examining the effect on load management.
The Homebots technology is said to be the first application in the world based on intelligent software agents. These agents represent electrical appliances that can communicate over the low voltage power grid, enabling decentralised optimisation of energy-use efficiency and cost.
An early version of the Homebots technology was installed in Villa Wega for preliminary testing. The results demonstrated that this can deliver these services over the power grid within the real-time constraints with low data transfer speeds.
The final Homebots system is expected to consist of a large number of interacting agents. The project investigated how these agents interacted, and what the global results of such a system would be. Examples of the research issues are:How and what would utilities and customers want to communicate? How are utility and customer preferences specified in ISES? What are the economic and environmental implications of applying advanced IT to energy systems? How are efficient, robust and secure coordination and negotiation mechanisms constructed? How are energy related services integrated with other IT services? What are the properties of different communication methods?
It was found that, if real time pricing was introduced to customers with controllable equipment, these customers used their load priority system the whole year, and not simply during the cold season. The benefits of real time pricing corresponding to real time load management is totally dependent on the variation of price, and was not affected by seasonal movements or by the absolute price level.
The instant gain for a distributor from active load management arises from reduction to their own power-related charges to the grid owner. Another main reason to perform load control is to avoid or postpone heavy investment in extended distribution capacity.
The implications of the tests
It was found that, when customers could control their load management, there was a trend towards evening up their power costs.
Furthermore, the use of intelligent, automatic appliances as used in the Homebots technology gives the utility the ability to exert greater control of sags and surges in power demand. Being able to turn off, freezers, for example, a a brief period during a surge, the utility can even out demand levels. Customers can be offered contracts that allows the utility to do this for specific appliances. It becomes possible for utilities to offer separate tariffs for different appliances. Thus customers can specify high priority appliances (at a premium) that the utility guarantees to keep running, and low priority appliances that can be turned off without harm.
To develop this possibility to its full potential requires good PLT technology, with information from each appliance passing reliably to a sophisticated database manager. The IT capability is unquestionably possible; the PLT technology is not quite ready. Nonetheless, the initial indicators are very promising.
The PLT technology that is closest to becoming commercially viable is automatic meter reading. This application does not require high bit-rate data transfer. Other possible services that are on the verge of viability include:Monitoring systems; Tariff reading; Load distribution; Security systems; Alarm systems; Network communication.
The future prospects
Looking to wider issues, Enersearch carried out a general survey of what utilities' expectations for the future were, with specific reference to the applications and usefulness of PLT. Most of those surveyed believe that there will be a host of new services to which PLT could be applied. These include:Vending machines; Security systems; Home shopping and home banking; Internet and e-mail; Building monitoring systems; Street and traffic light control; Monitoring systems; Inner city and motorway/freeway tolls.
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