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How to Use Thermal Resistivity Testing Before You Sink Your Cables

If you want to develop an area for a new residential or commercial project, you need to investigate the suitability of the terrain and, specifically, the soil. This will help you determine whether you can install underground transmission cables or pipelines to help service your development within the existing soil or if you may have to modify the material for the purpose. To help you answer these questions, you should commission soil thermal resistivity testing. What does this involve?

Understanding the Process

Thermal resistivity testing helps you learn whether the soil is able to conduct or dissipate heat effectively, given your intended project. If you were to sink your cables into the wrong type of soil or use the wrong specification, it could lead to premature failure, downtime and unwanted cost.

In short, thermal resistivity tells you whether the heat generated by these cables or pipelines will be dissipated effectively when they are activated. A major underground power cable will generate a lot of heat when current is switched on, and in the worst-case this could cause the cable to melt. Once you know the resistivity of the soil, you can either change the insulation or capacity of the cables or add backfill in the area around the trench to correct matters.

How to Test

To get your answer, you will need to use specific equipment that can be introduced to the proposed depth of the installation. This will usually be a handheld device connected to a cable, which includes a heat and temperature sensor within a needle. This probe is inserted to the required depth before the current is activated through the heater. Readings are then taken over a specific period of time through the sensor, and this can then be analysed to determine the thermal resistivity of the soil in question.

Using the Data

Using this information, you'll be able to order the right specification of cable for your electrical connection and/or introduce thermal backfill that is more appropriate. In the future, you will be able to conduct spot checks using the same equipment to make sure that heat is being properly dissipated from your existing installation.

The Importance of Testing

This is just one of many different tests available to help you make the most of your underground installations. It's best if you bring in an experienced technician to help gather this information though, as there is a lot riding on its accuracy.