Natural gas supply planning has become significantly more complicated For the local distribution comapany company in recent years due to changing governmental regulations, competing energy sources and increased regulatory pressure. Illinois Power Company, a gas and electriculity serving a wide area of Illinois, uses Energy Management Associates, Inc. 's SENDOUT" gas planning software for best-cost analysis of supply and demand alternatives. This paper reports on the planning problems facing Illnois Power and the methods used to analyze these problems.


Local distribution companies (LDC) such as Illinois Power have fa ed significant changes in their business environment during the past several years. These changes include uncertainty regarding price and availability of supply, increased conservation, potential loss of larye industrial customers to other fuels and, perhaps most significantly, a substantial increase in the focus of state regulators on least cost gas planning, The need to demonstrate prudent planning practices and operating policies under changing conditions has made resource planning much more difficult and much more important for LDCs. Faced with the requirement for a tool to analyze alternatives in this changing environment, Illinois Power turned to Energy Management Associates' SENDOUT software system. SENDOUT gives Illinois Power the ability to describe its distribution system in detail and assess the impacts of various scenarios on system operations, reliability and cost. This paper di scusses Illinois Power Is gas planning process, the SENDOUT system usea at Illinois Power to analyze gas supply planning issues, and examples of gas supply studies performed by Illinois Power's Planning Department. Illinois Power Company, an investor owned gas and electric utility, serves natural gas to approximately 382,000 customers in northern, central and southern Illinois. Illinois Power Company's natural gas system consists of approximately 7,200 miles of transmission ana distribution system, eight company-owned storage fields and two active propane plants. The company currently purchases gas under six pipe1 ine contracts from five different suppliers at approximately 70 delivery stations. A map of the company's service territory is shown in Figure 1. For a more detailed description of Illinois Power's gas system, see Appendix A, The LDC Planning Problem LDCs today face the problem of obtaining a portfolio of supply contracts and operating policies that minimize costs while ensuring adequate reliability to firm customers. To meet this objective, we must consider the following:

  • The fixed costs of building/reserving sufficient flowing gas capacity and storage for customers' needs.

  • The variable costs associated with buying gas, including commodity, transportation and storage costs.

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