March 10, 2003
WinMon® Interface and Automatic Capacitor Controls Help Midwestern Utility Stabilize System.
Background
The value of capacitor automation has been clearly demonstrated at a midwestern utility. S&C’s WinMon® Graphical User Interface and automatic capacitor controls are key components in the midwestern utility’s progressive capacitor automation program, which they started in 1994 to support VAR and voltage regulation.
The midwestern utility’s system is dependent on metropolitan-area generation for system voltage control. During outages involving this generation, and during summer peak-loading periods, the midwestern utility’s Transmission System Operators use the WinMon interface to issue requests to turn on all available distribution capacitors, to support system VAR and voltage needs.
In August 2000, the midwestern utility set the highest system electrical peak for that year. Transmission System Operators were concerned about projected low-transmission-voltage levels under peak conditions, as temperatures were expected to reach the mid to upper nineties, with a heat index well over one hundred degrees. Consequently, they requested that all distribution capacitors be switched on.
What did they do?
Using the query tool of the WinMon interface, shown below, the midwestern utility readily identified over 160 capacitor banks that were open. The query tool wizard leads users through the process. Users choose the type of control and conditions in which they are interested (for example, VAR with neutral Current Controls with “CapBankState = OUT”). They can also choose to include other information in the query. The query tool automatically generates a list of controls meeting the criteria.
The global command feature of the WinMon interface let the midwestern utility quickly switch capacitors from their normal VAR/voltage strategy to a strategy that forced capacitors on, while providing automatic voltage protection. Users can make a global change to any device of the same type. They select a new set point value as usual, as well as “Global” in the Change Value dialog box. Using the query results, they can then execute the global change in the Global Change window. If any problems occur due to failed communication, wrong device type, etc., the results are shown and logged as shown below.
Results
Although many of the midwestern utility’s off-line capacitors would have turned on later in the day as the load increased, capacitor automation allowed the midwestern utility to switch them on proactively and supply needed VAR support before the peak-loading period. As a result, the immediate system operating requirements were addressed and the service quality needs for the midwestern utility’s customers were maintained.
The CEO and President of the midwestern utility stated, “The automatic capacitors gave us the needed advantage to better manage our system. There are many benefits as a result of our capacitor automation system, but perhaps the most important is the fact that our customers continue to receive superior service quality for their homes and businesses.”