Temperature Dependency of Transient Signal Propagation in Underground Power Cables

The temperature dependency of transient signal propagation in multi-conductor power cables is investigated. The sensitivity of the propagation velocity variation upon temperature is studied for a mass-impregnated medium-voltage cable in service. Data on almost one year monitoring of a medium-voltage cable with dynamic loading indicate that temperature differences down to 1 °C can be detected from the signal propagation time. This sensitivity opens the possibility to make use of signal propagation information for dynamic rating of power cables. To this end, the signal propagation modes are investigated for a three-phase medium-voltage cable based on a simulated temperature distribution for a loaded cable and the measured temperature dependency of the permittivity.