researchers at tu darmstadt (germany) are studying the effective thermal conductivity of cable bedding materials used in the underground energy distribution grid to determine the extent of the load that the materials can handle and ensure continued operation and efficient expansion of the grid.
professor ingo sass, christoph drefke (right) and markus schedel (left) in the lab.
(sandra junker/tu darmstadt)
according to a report on the university website, researchers are working at a test site in the german town of griesheim. the site has 90 temperature sensors, 16 water tension sensors, and 20 moisture sensors to measure interactions between the cables and the ground under various loads and environmental conditions.
“if cables dissipate heat in the course of conducting electrical power, the surrounding bedding substance dries and its thermal conductivity is reduced,” the article explained. “these interactions are by no means trivial, for excessive thermal loading lowers the durability of the electrical insulation of the cable material. extreme cases can result in outages and concomitant power supply bottlenecks.”
it continued, “in particular, the scientists also want to know the extent to which short term load spikes, of the kind that result from volatile energy sources such as wind and solar, can adversely affect the cable load capacity. the successful collation of reliable thermal conductivity data and development of corresponding analytical and forecasting processes would enable power grid operators to optimize their use of existing cabling systems and to undertake the expensive expansion of the national grid, which the energy transition has made necessary, in a more cost-effective manner.”
cables used for transmitting medium and low electrical power are typically underground in germany and, despite wide distribution of the cables, there is no diagnostic tools to determine the condition of the systems. the assumption of experts is that the cables are operating well below their thermal load capacity.
studying the existing cable system to incorporate it into an “intelligent operations management system” that would increase load levels by 10-20 percent could be possible based on a better understanding of the cables’ thermal properties.
“to this end, researchers use the dissipated heat from buried cables to desiccate different bedding materials and soils in a targeted manner and under predefined conditions, and precisely measure the development of thermal and hydraulic properties over time,” the article said.
lab and field experimental data was used to create mathematical models that could be used to identify “highly-stressed sections of the cabling systems in advance and either reduce the load temporarily or else install bedding materials in these hot spots for long-term stress relief.”