ABSTRACT
As the residential consumer has higher priority to receive the gas than the thermo plant, the source fluctuations affects the thermo plant supply. Normally the consumers demand is supplied by the source, being eventually disturbed by failures at the compressor station or at the source. All failure rates were considered to be exponentially distributed and the repair durationwere represented by rectangular distributions. The compressor station shutdowns occur in average once in a year with time to repair varying between a minimum of 24 h and a maximum of 48 h. The gas source has two different types of failure: total shutdown and flow reductions. It is being considered that source shutdowns occur on average four times in a year with duration between 48 h and 72 h. The gas flow reduction by half occurs also 4 times in a year with duration between 24 h and 48 h. In case of source failure, the pipeline has normally a volume of gas stored that is enough to supply the consumers around ten hours after the failure (line-pack volume of 500 mscm).
