ABSTRACT:

Several methods are presented for estimating system demand for use with computer modeling of a natural gas distribution system under design and/or peak conditions. In a sense, a "system" model consists of two separate "models" - a configuration model, and a demand/load model. The configuration model consists of data describing the physical system - basically the hardware of the system. The demand model consists of data describing the load and usage information associated with the gas appliances and equipment connected to the system. Demand data includes information about total connected load, load diversity and coincidence, cumulative usage and ideally some knowledge of the demand response to temperature changes. This paper will discuss some of the various methods used to estimate and model the demand portion of the system model.

INTRODUCTION

Modeling of a natural gas distribution system allows conditions and configurations in an actual system to be simulated in a nonoperational environment. For the purposes of this paper, modeling shall refer to computer modeling of a gas distribution system using specialized network modeling software. These software use various mathematical representations of the system components to define the system within the computer environment, simulating the pressure and flows in the system, and the response of the system to changes in demands and configurations. System models are used as both a design and an operational tool, generally to answer what-if questions about the system. For example, what if we add this new subdivision, what if we remove this section of line from service, can we retire this regulator station, what is the best location for a new gate station, what size should be used to replace this leaking main. Often the data used to answer design questions are different than the criteria and data used to answer operational questions.

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