The need for comprehensive transient analysis of distribution systems

Many surge analysis and design rules have evolved over time to help utilities cope with the complexity of transient phenomena. These rules have been widely applied to simplify analysis by restricting both the number and difficulty of the transient cases that need to be evaluated. On further reflection, however, the implicit assumption that elementary and conservative rules are a valid basis for design has often been shown to be questionable and sometimes dangerous. Indeed, many published guidelines are so misleading and so frequently false that they should only be used with extreme caution, if at all. This article specifically reviews a number of guidelines or suggestions found in various AWWA publications for water hammer analysis and provides a set of warnings about the misunderstandings and dangers that can arise from such simplifications. The authors conclude that only systematic and informed water hammer analysis can be expected to resolve complex transient characterizations and adequately protect distribution systems from the vagaries and challenges of rapid transients.