The cost of electricity for pipeline pumping stations is a considerable expense. Monitoring the power in use and calculating its expense are necessary for cost-effective operation of a pipeline. The contracts for the cost of electricity are frequently dependent on time of day and/or coincident grid load. A real-time system adjusts cost calculations according to these real-time conditions. Accurately modeling each utility contract is an important part of a real-time cost analysis system. A graphical overview of the power information and summary tables of past and present costs provides a powerful tool for managers seeking to control electricity expenses. Background Cochin Pipe Lines transport propane, ethane, and ethylene. It is 1900 miles in length with 23 variable frequency drives and 10 variable speed drives. All drives are electric and there is one per station. Each drive is rated at approximately 3 to 5 megawatts. A typical electrical bill for the pipeline is approximately a million dollars.
If you need to manage something, you need to measure it first. The pitfall of many attempts at management and, in particular, computer-based optimization, is the failure to have good data. In this case the goal is to achieve a high quality of measured data for electrical power and cost in order to properly manage and optimize the cost of electricity. Measurement of electrical costs is extremely complicated. Even though contract terms are designed to influence when and how much electricity is used, the details of these terms are so involved that they are frequently lost in real-time operations. Electric utility contracts are complicated. Most pipeline controllers don't have access to the detailed information, which is secondary to their job of meeting deliveries. In fact, the control of power costs can put a constraint on the controller's ability to make deliveries unless there is enough flexibility in the pipeline's capacity to make changes to reduce costs. For a pipeline to be a candidate for power cost reductions means that the pipeline schedule must be flexible. The complexity of the contracts means that a software tool is needed to assist the pipeline controller and the power manager. The complexity also means that the contracts are not something that can be implemented in the SCADA system. After working with electricity contracts for some time, I concluded the only common element among them was that they billed monthly. In fact, the monthly meter-reading date is critical in the management of costs. If all utilities read the meters on the same date, there isn't a problem. Some utilities like to have meter-reading dates of the 10th, 15th, or 20th of the month. Experience has shown that different meter-reading dates cause a problem. Stations with different meter-reading dates are difficult to compare. While prorating and averaging can be used to extrapolate to the first of the month, these techniques are not accurate enough because the maximum demand may occur during the period of extrapolation.