Abstract
Temperature variation from dynamic cable loading affects the propagation characteristics of transient signals. The distortion of modal signal components as a function of temperature in a three-phase medium-voltage cable is investigated. The temperature influence arises mainly through the complex insulation permittivity, which has a non-linear relationship with temperature. Near the maximum operating temperature of the cross-linked polyethylene insulation, the propagation velocity increases by 0.56% per degree centigrade but is an order of magnitude less sensitive at ambient temperature. The paper presents modeling results based on cable impedance and admittance matrices obtained from electromagnetic field simulation, taking into account the time-varying temperature distribution in the cable cross-section. The results are verified by applying Rayleigh–Schrödinger perturbation analysis. In the time domain, signal patterns shift when the modal propagation velocities change upon cable loading. Moreover, separation of degenerate modes is observed when the cable phase conductors carry an unbalanced current. The perspectives for exploiting the temperature dependency of signal propagation for pinpointing cable defects and for dynamic rating of underground power cables are discussed.
Highlights
Defects in underground power cables can be a source of partial discharges
These events concern transient short circuits, typically lasting for a fraction of a power cycle, which is too short to directly cause a system outage. These events may act as a precursor for an upcoming failure. In both examples, pinpointing the fault location requires accurate knowledge of the propagation of the transient signals caused by these events
The variation is estimated to be around 0.10%/°C [3]. This sensitivity suggests that signal propagation velocity is a feasible based on averages hour of the measured times
Summary
Defects in underground power cables can be a source of partial discharges. Partial discharge (PD). This recording is obtained from online monitoring of a cable connection on PD activity over almost one year. The variation is estimated to be around 0.10%/°C [3] This sensitivity suggests that signal propagation velocity is a feasible based on averages hour of the measured times. Measured variation signal propagation velocity a 1195 mass-impregnated cable from load cycles during fourfour weeks’.
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