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Reliability in Power Delivery: Where Technology and Politics Meet

Fortnightly Magazine - January 15 1998

up to 40 percent. These controllers also improve overall system reliability by reacting almost instantly to disturbances. Four FACTS controllers are already operating on utility systems, with more to come. American Electric Power Co., for example, is installing at its Inez substation in eastern Kentucky the most advanced FACTS device, known as a "unified power flow controller." To achieve widespread utility use of FACTS, researchers must reduce the cost of individual controllers to get them ready for mass production. This next generation of devices should be inherently more cost-effective and energy-efficient.

A "wide-area measurement system" uses real-time information to monitor conditions throughout a group of neighboring power systems simultaneously, detecting abnormal conditions over the horizon. It allows controllers to correct disturbances before they spread. WAMS works like this:

Step 1: Satellites send signals to sensors that affix a "time-stamp" to data at numerous points throughout multiple power systems.

Step 2: These data are sent to control centers, which analyze the information to check for abnormal conditions.

Step 3: Control centers then share this information, allowing adjacent regions to coordinate their operations.

The first WAMS is being developed for the western transmission network. However, the problem of assimilating and communicating all the data produced by WAMS remains a major gap in technology development.

Of course, operators will need the right tools to interpret the information supplied by WAMS in real time, to send commands to the control devices that maintain stability. Such online analysis allows expert systems to optimize network configuration for maximum power transfer. Such online system analysis is just beginning. The first generation of online software, now available, provides operators with near-real-time information on system conditions - but not the ability to analyze in realtime. Ultimately, this sort of analysis will require the use of parallel processing computers, now in the early stages of development.

Finally, we need to be able to tie together FACTS, WAMS, and online analysis into an overall control scheme. Called hierarchical control, this system will coordinate the intelligent local operation of power flow devices with broader system needs. Local control of transmission devices now exists. In the future, more of the burden of control will need to shift to centralized control centers to make transmission capacity more dispatchable, in much the same way that generation capacity is dispatched today.

Distribution Systems: More Options Needed

Retail deregulation means more choice among a wider range of services. Utilities must customize services in a way that will attract and hold diverse groups of ratepayers. Specifically, technologies are needed that can:

•  Provide perfect power to customers with sensitive

equipment;

•  Offer rate flexibility to customers concerned primarily with cost;

•  Integrate multiple utilities services for customers who want the convenience of one-stop shopping.

Again, several specific technologies are becoming available that can help fulfill these needs. "Custom power," for instance, is a type of power electronic controllers designed for use on distribution systems. Custom-power devices

provide the key to enhanced reliability on distribution

systems. One custom-power device, for example, the "Dynamic Voltage Restorer," or DVR, smooths out power disturbances