The 1000 kW Cummings diesel generator offers seven stages of functionality, from off at Stage 0 to maximum generation at Stage 6.
Click here to enlarge imageOne meter monitors the incoming utility service at the main SCE&G substation where the utility load for the town is monitored. The meter monitors utility power levels for demand control, and provides data that can be used for bill verification to ensure accurate billing on the part of the utility.
The other meter monitors and controls the generator at the treatment plant. A workstation running Enterprise is located at the treatment facility as well. The substation meter is connected to this workstation through a continuous modem link; the generator meter is connected through RS-485 serial connection.
The generator switches on when the utility reading reaches a set-point value defined within Enterprise. The generator output makes up the difference between the current load (power consumed) and the defined peak shaving setpoint. As demand grows above the setpoint, the generator is stepped up to increasingly high output levels. When demand levels drop, the generator switches down to lower stages until it switches completely off. The stepped approach allows the generator to tailor its output to best meet the demand, minimizing wasted capacity and less money wasted on fuel and generator maintenance.
Relevant Information Only
A number of customized specific screens and functions (frameworks) were created to maximize the hardware and software elements of the system. These included processes to verify the accuracy of the substation meter and to calculate continuous demand levels for each 30-second period, as well as frameworks to enable communications and control functions for the generator. Because the frameworks are specially designed for McCormick's application, the screens provide only the information needed without confusing users with irrelevant information or unnecessary data.
The software system features graphical screens that provide a simple interface to a wide variety of information, including a main screen that shows the current reading from the substation meter, the current reading from the generator meter, and the current status of the generator itself, including its operational stage. From this screen, users can access alarm information, reports and master controls, as well as connect or disconnect the modem link to the substation meter.
Subsequent pages offer more detailed information and control, including a manual generator on/off switch, generator run-time controls to limit how long the generator can run without interruption, information on the maximum demand levels pre-set for each month, and the current peak demand level. Users can easily check or modify any setting, no matter how detailed, through the logical and intuitive system structure.
The Ion system is also intelligent, automatically making adjustments to optimize demand charges. If the peak demand level for the month is exceeded, peak setpoint is re-set at the new higher level, so that the facility doesn't run the generator when it is already paying the demand charges for that level of power from the utility. This saves the town money by reducing fuel usage, and saves time and effort because the automated function means that no person is required to constantly monitor the settings, checking for potential inconsistencies.
Remote Access
The system's web-enabled communications allow Bernard Welborn, the administrator for the McCormick Commission of Public Works, to oversee the system remotely, dialing in daily through his laptop from his home or office. He can monitor conditions, adjust setpoints, and check on fuel levels without having to drive out to the wastewater facility site, ensuring fast, effective response to changing conditions without unnecessary and wasteful travel time.