Why does it matter what soil surrounds your cables?
If you are laying a network of electrical cables, then you will probably have been thinking about everything involved in the process. You will have been considering the type of cable you need, the route it will follow and how you will connect your cabling to the rest of the network. What you may not have been considering yet is the thermal resistivity of the soil. Thermal resistivity is an area that is often overlooked by designers but which can have a significant impact on the performance of electrical cables that are buried in the soil.
Why thermal resistivity matters
Every electrical cable needs to dissipate heat. If the cable isn't able to dissipate heat properly, the working life of the cable will be shortened, and in some extreme cases it is possible that catastrophic failure could occur. If the cable is in the open air, then the air carries away the heat, but if it is buried in the ground, then it is the soil surrounding the cable that is used to propagate the heat. It is the effectiveness of the soil in propagating the heat that dictates the performance level of the cable. Identifying the thermal resistivity of the soil allows you to select the most appropriate alignment or cable rating for a given project or to improve the resistivity of the soil surrounding the cable by selecting a more conductive backfill material.
Discovering your soil thermal resistivity
The only way to discover how conductive your soil may be is to arrange for a company to carry out soil thermal resistivity testing on the soils you will be using around your cables.
Soil thermal resistivity testing involves taking a collection of representative soil samples from the area in which the cables will be installed. These soil samples will be dried and their thermal resistivity tested with varying amounts of moisture present. Generally it is the case that the more water there is present in the soil, the lower the thermal resistivity will be. If the soil thermal resistivity shows that the heat dissipation of the soil is not suitable for laying cables, the testing company will be able to suggest a more appropriate backfill material for your purposes.
Don't risk your electrical cabling failing because the heat cannot dissipate properly. Make sure you arrange for soil resistivity testing and discover whether you have the right cabling on the right alignment or whether you would be better advised to use an alternative backfill material that will enable your cabling to cool more quickly.