ABSTRACT

The Australian Gas Light Company is supplied with natural gas from a single source of supply through a 1300 km (830 mile) long, 860 m (34 inch) diameter pipeline. Due to the nature of the market, and the dynamics of the pipeline, flows and pressures follow both a daily and weekly pattern. Transient analysis is used extensively, not only for design purposes, but as an operating aid to assist gas dispatchers in control of the system. An existing transient analysis program has been modified so that it can be easily operated by the gas dispatchers. Standard flow profiles have been developed to simplify data input and this minimises the time required to set up each run of the program.

INTRODUCTION

The Australian Natural Gas Industry is characterised by scattered markets supplied through single pipelines from relatively remote sources of gas, as illustrated in Figure 1. At first inspection this is a very simple network - although "network" is hardly the correct word - but this simplicity brings its own set of problems. Problems such as: single sources of supply; long pipelines through inhospitable regions; and the lack of suitable gas storage close to markets. The market is therefore very exposed to disruptions as a result of pipeline failures or supply difficulties at the gas fields. It is in this context that transient analysis can, and does, make a significant contribution to the management and operation of these pipelines, and is thus a valuable aid to ensuring continuity of supply to the consumers. In this paper attention is given to the Moomba - Sydney pipeline system, (which includes extensions to the industrial cities of Newcastle and Wollongong, as well as branches supplying major regional centres (Figure 2). The practical application of transient analysis for pipeline planning, operation, emergency simulation, and training will be discussed.

THE AUSTRALIAN GAS LIGHT COMPANY

The advent of natural gas in Australia is quite recent, dating from the latter 1960s, and summarised in Table 1. However, the gas supply industry itself is well established, with the first gas company, The Australian Gas Light Company (AGL), being founded in 1837 by a group of public spirited citizens, and first supplying gas in 1841. Table 2 contains a brief summary of the Company's development since that time. Today, AGL supplies natural gas to about 450,000 consumers in Sydney, Canberra, Newcastle, Wollongong, and several other major regional centres. When significant quantities of natural gas were discovered in Australia during the 1960s, the Company decided that supplies of this fuel should be brought to New South Wales. Natural gas arrived in Sydney at the end of 1976, and since then the gas load has increased by a factor of ten, mainly through penetration of the industrial market, At present, about 80 percent of gas is sold to industrial consumers (Figure 3). This large industrial component has major implications as far as system control is concerned, and this point will be discussed later in more depth.

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