Exercise EE1-04.R1

Prof. Dr. Thorsten Jungmann (last updated 2025-12-09)

Relates to EE1-04 Resistance

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Task

During the installation of a photovoltaic system, an earthing cable made of copper is laid (${\rho }_{Cu}=1.78\cdot 10^{-8}\mathrm{\Omega }\cdot \mathrm{m}$). The electric line has a length of $l=25\mathrm{m}$ and a cross-section of $A=16\mathrm{m}{\mathrm{m}}^2$.

a) Calculate the conductor resistance of the earthing cable at $20°\mathrm{C}$.

b) What is the conductance of the earthing cable?

c) In the event of an earth fault, a current of $I=100\mathrm{A}$ flows briefly. What voltage drop occurs across the earthing cable?

Solution

a) $R=27.8\mathrm{m\Omega }$
b) $G=36.0\mathrm{S}$
c) $\Delta U=2.78\mathrm{V}$

Full solution