IEA-DHC-project: Improvement of operational temperature differences

Two methods developed and applied within an IEA-DHC-project for detecting malfunctioning substations based on the evaluation of the excess flow of substations are discussed. The two process include: excess flow method and target temperature method. Excess flow method answers essentially the question of how a substation would perform, if the return temperature is below the actual average value of the return temperature. An ideal return temperature called target return temperature (TRT) can be defined, depending on some operating and climatic conditions. This temperature is neither a given nor a constant temperature. A critical step in the effort of decreasing the return pipe temperature is the diagnostic work and the repair of malfunctions.