Planning engineers today have numerous pipeline simulation software applications available that can be used to analyze, design and optimize pipeline systems. However, Pacific Gas and Electric Company (PG&E) has found that a significant amount of the process of performing systems engineering for local transmission pipeline systems consists of manually gathering and organizing multiple sources of customer and operating data in order to build the necessary model input files. PG&E engineers decided to invest time looking for ways to simplify and automate many of the tasks involved with building models so they could increase the amount of time spent designing and optimizing local transmission pipeline systems. This paper will:
Provide an overview of how local gas transmission system model building used to be done at PG&E and the issues involved;
Describe the project goals and the solutions that were developed to improve the process;
Provide a description of the software applications developed.
Summarize the results and the benefits obtained; The paper discusses the significant efforts taken by PG&E over the past few years to reduce model update time and improve model accuracy.
Accurate modeling of local transmission pipeline systems is essential to provide reliable simulation results. These results impact the quality of the analyses performed to support operating and capacity investment decisions, and ultimately determine how much money will be spent on pipeline system investments. Any substantial error in modeling accuracy can result in millions of dollars being unnecessarily spent for capacity investments. Although the overall customer load forecasts used in the models conformed to prescribed design criteria, the process of allocating the design loads to specific pipeline models did not. As a result, different loading assumptions, tools and techniques were created and used by the various transmission planners over the years to build the models. Many of the techniques used involved manual data gathering and assigning of loads to the models and were often timeconsuming with a high potential for error. Because the process of building and updating models required so much time to complete, operating and design decisions at times had to be made using older models. When sufficient time and resources were available to build a model, there was often little time left for the planners to analyze, optimize and design the systems being studied. The different loading tools and techniques used also resulted in varying degrees of model accuracy. When the time came to rebuild of some of PG&E's largest gas transmission system models, the task of redesigning the model loading process was initiated with the following objectives:
reduce the loading time; and
improve simulation accuracy.
The PG&E gas system serves over 3.7 million gas customers in northern and central California from the Oregon-California border in the north to Bakersfield in the south, and from the Pacific Ocean in the west to the Sierra Nevada foothills in the east.