Radio Systems for DA/DSM

Radio Systems for DA/DSM

By Trevor A. White, Schlumberger

The availability of accurate and timely information is vital to any business`s survival today. For utilities, this means provision of communication systems that provide metering, monitoring and control capabilities to match the needs of the service provided. These communication systems form the core of the various applications that go under the labels of AMR, DA and DSM.

It is important to know early on what applications are required or expected so that the communications architecture and capacity can be appropriately dimensioned. At one end of the scale, there is a simple radio broadcast DSM scheme where a single territory-wide transmitter sends control signals to all homes within range without any acknowledgment to turn on or off air conditioning units. This is a one-way, low-data content short message that is infrequently sent.

At the other end of the scale, there is a service of real-time pricing to a large industrial customer, where the pricing is determined by the instantaneous power consumption in the overall network. This communications infrastructure is a two-way, high-data content network with a large number of frequently downloaded complex messages.

Key specification issues include response time, capacity, message reliability, protocol, class of service, and conformance to existing communication standards.Just as protocols are now defined in separate layers to simplify ease of interconnection, modern-day communication networks may be divided into the WAN, providing long distance interconnect with appropriate matrix communication, and the LAN providing a geographic or logical grouping of nodes.

The basic concept of a radio LAN is a local data concentrator that covers a certain geographic area, or cell, containing the various nodes to be monitored or controlled. The data concentrator in turn communicates with the WAN to download or upload information as needed. Multiple cells are used to cover the required territory. Of course, full coverage is not essential from day one, allowing the system to grow as the need grows. The design of a radio LAN is basically dependent on parameters such as frequency, power, license type, etc. The choice is regulated by the appropriate authorities and affects communication range, reliability and data throughput.

The WAN provides the communication between the many LANs and the host computer system. This WAN could use a variety of media including telephone, radio, fiber optics and satellite. These media could in turn be dedicated private networks set up by the utility of common carrier networks, such as the public telephone company.

In recent years, there has been a proliferation of radio-based public voice and data networks. Here we meet a plethora of acronyms. Under development or already available are mobile radio telephone systems under the personal communication services umbrella including GSM (Roupe Systàƒ©me Mobile), DECT (Digital European Cordless Telephone), and DCS1800, together with various paging systems such as ERMES. Data over cellular telephone systems is being promoted under the CDPD (Cellular Digital Pocket Data) label.

The key issue is whether the utility should use a public or private radio data network for DA/DSM applications. Public, common carrier, radio networks can provide advantages of economies of scale and wide coverage. However, spectrum is limited and must be shared and so access, and therefore response time, may be unsatisfactory for utility applications such as on-request read or network switching. In times of emergency, such as a storm, the utility needs to be able to continue to monitor and control the service. If a public network is used, this may be already overloaded with public use, blocking utility communication completely.

Most utilities have a land mobile radio system (often termed private mobile radio or PMR) used for voice and data communication to and from mobile field installation and maintenance teams. Usually, this will cover most, if not all, of the utility`s service territory. There are various forms of land mobile radio systems, including analog and digital, conventional and trunked.

The coverage plan of today`s cellular systems is focused on centers of population and may not be sufficient for the utility`s service territory. Also, a cellular telephone system is not designed for the level of reliable communication performance that is needed of a utility system with its fixed-end nodes. Cellular systems rely on the fact that users expect “holes” in communication and will move around to re-establish communication at a later time.

That is not to say that public networks in general should not be used. A local network that is a private system can be complemented by a WAN that is a common carrier such as wire-based telephone which has good access, is battery-backed and well meshed. An even more interesting possibility is synergistic reuse of existing utility telecommunications systems for the WAN. For example, an electricity utility may have optical fiber passing close by that is used for DA.

In general, this radio WAN can be reused as the data highway between the host computer system and the data concentrators. It is a very cost-effective way of providing full AMR coverage of a territory. Most utilities also have SCADA systems for monitoring and control purposes that may be reused as part of the WAN communications infrastructure. Once a suitable communications infrastructure is in place, it is readily possible to extend to other value-added services, such as security and health monitoring.

Author

  • The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at Jennifer.Runyon@ClarionEvents.com.

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at Jennifer.Runyon@ClarionEvents.com.

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