Thermal resistivity: Real RHO values for the professional power engineer
Understanding a soil’s thermal stability can help power engineers more accurately design power distribution systems to prevent thermal runaway.
Soil thermal resistivity
Measure, don’t guess. Even in a well-designed underground cable system, the soil may account for half or more of the total thermal resistance. Soil and backfill thermal properties should not be assumed. These properties are easy to measure in the field and in the lab. A safe, professional installation requires actual measurement and evaluation of thermal rho.
Education guides
Do bad rho values lead to power failures?
Even in a well-designed underground cable system, the soil may account for half or more of the total thermal resistance. A safe, professional installation requires actual measurement and evaluation of thermal rho.
Accurate ampacity calculations depend on measured rho values. That’s why you need an accurate—and compliant—thermal properties analyzer. The TEMPOS is a fully-portable field instrument that can make measurements in as little as one minute. VARIOS is a precision lab instrument that automates thermal dryout curves, eliminating human error and wasted time. Both are backed by 40+ years of research experience on heat and mass transfer in soils.
Measurements made easy. Unlike competitor instruments, which use a one-sensor-fits-all type system, the TEMPOS field instrument automatically optimizes the reading for your material at the push of a button. In the lab, VARIOS makes it easy to measure thermal conductivity as a function of water content. Just insert the needle and start measuring. It’s that simple.
“For a soil instrument, it makes a lot more sense to go to people that have more expertise about soil science and soil measurements than we ever would at JPL. The thermal and electrical conductivity probe (made by METER) was probably the only instrument on the Phoenix Lander that worked perfectly from beginning to end.”
– Dr. Michael Hecht, NASA JPL
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measurement insights
Thermal properties of stony soils: How to get the right answer in a soil/rock mix
Get the right thermal conductivity or thermal resistivity value for your soil profile. Find out how to combine rock and soil measurements.
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There’s no way to measure the properties of moist, porous materials with the steady state method (guarded hot plate). The transient line heat source method, however, is able to measure the thermal properties of moist, porous materials, and it can even measure thermal conductivity and thermal resistivity in fluids.
Why underground power cable installations need soil thermal resistivity measurements
Soil physics is increasingly critical in the design and implementation of underground power transmission and distribution systems.
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