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The equivalent resistivity calculator is designed to determine the thermal resistivity of cable insulation or jacket materials composed of multiple layers with varying thermal resistivities.
Posted 2025-01-21
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New feature
, Tools
When modelling high-voltage electrical power cables, it is essential to define the physical and thermal properties of the insulating layers. This calculator simplifies the process by combining the thermal resistivities of adjacent layers made from different materials into a single equivalent value.
For instance, if a high-voltage cable has a semi-conducting coating or a termite-protective sheath layered over its outer jacket, this tool can calculate the overall thermal resistivity of the two layers combined. This can be useful for more accurate thermal modelling and determining the cable's current-carrying capacity.
The following shows the input parameters and the preview. Note that thickness of layers 3 and 4 are optional.
| preview | input data |
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This example would result in:
The equation to calculate the equivalent resistance of all layers combined - each with its own thickness and distinct thermal resistivity - is given as
\[ T_{eq} = \frac{1}{2 \pi} \cdot \left[ \rho_1 \cdot \ln\left(\frac{D_1}{D_0}\right) + \rho_2 \cdot \ln\left(\frac{D_2}{D_1}\right) + ... + \rho_n \cdot \ln\left(\frac{D_n}{D_{n-1}}\right) \right] \]From this equivalent resistance we can now calculate the equivalent resistivity of a fictive layer with the same thickness and a homogenous material.
\[ \rho_{eq} = 2 \pi \cdot T_{eq} \Big/ \ln\left(\frac{D_n}{D_0}\right) \]