ABSTRACT

Fluctuating flow demands and increasing fuel costs for the Pacific Gas Transmission Company (PGT) pipeline has emphasized the need for a tool which could aid in making prudent decisions concerning efficient pipeline operation. A computer assisted fuel optimization program utilizing a dynamic programming technique has been implemented by PGT to help in operating its interstate gas transmission pipeline. This paper describes PGT's approach to obtaining an optimizing program, our applications of the program and our experience with the program. The program has proven to produce simulation results within 3% and demonstates the potential for considerable fuel savings. A companion paper by Ms. Jill Gilmour describes the development of the program.

Introduction

Pacific Gas Transmission Company (PGT) and its Canadian subsidiary, Alberta Natural Gas Company Ltd. (ANG), own and operate segments of a natural gas pipeline which transports gas from the ultimate distribution to Pacific Gas and Electric Company (PGandE) customers in Northern California. Gas is also transported for other pipeline customers and delivered at various points along the pipeline. The ANG and PGT portion of the Alberta-California pipeline extends 718.6 miles traversing British Columbia, northern Idaho, Washington and Oregon. It consists of 36-inch pipe with 36-inch looping segments in ANG and 36 and 42-inch looping segments in the northern section of PGT. With its 15 compressor stations, which utilize gas turbine engines to drive centrifugal compressors, the pipeline is capable of delivering up to 1100 MMCFD of gas to California (Figure 1, Overview of PGT Pipeline). The typical station contains two gas turbine driven compressor units in series.The exceptions are Station 1 in the ANG section which contains three units in parallel, and Station 3 in the PGT section, with only one turbine/compressor unit. The recent changing flow and design conditions have allowed the PGT system to operate, at times, with substantially less horsepower than is installed, thus allowing a flexibility in the operation of the pipeline never before experienced. Alberta/British Columbia boundary to California for Gas is also transported for The ANG and PGT portion of the Alberta-California The exceptions are Station 1 in the ANG section, which contains three units in parallel, and Station 3 in the PGT section, with only one turbine/compressor unit. Given today's high cost of fuel, significant savings can be achieved with the selection of optimum modes of operation. PGT@s gas control operators needed a tool to aid in evaluating and choosing between alternative operating modes which would best achieve balanced pipeline operation with maximum compressor fuel economy or "optimization". Computer optimization models of pipeline operations were determined to be the most effective tool for this purpose. Computer optimization models of Past Operation and Optimization Procedures Gas control operators start, stop and regulate all 15 ANG and They are assisted by a PGT compressor stations and monitor the pipeline from PGT's operating headquarters in Spokane, Washington. supervisory control and data acquisition system (SCADA). The SCADA system scans the line every minute and displays all telemetered data to the control operator.

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