Abstract
One of the serious problems in 6-10 kV cable electrical networks is single-phase ground faults (SGF). SGFs, in turn, can lead to interphase short circuits (SC) and power line shutdowns if they last for a long time. However, until the FGD mode transitions to an interphase SC, the cable will be affected by elevated temperatures due to additional heating of the cable by higher harmonic currents (HHC). Additional heating by higher harmonic currents in a steady-state FGD mode can cause the cable temperature to exceed the standard for different types of insulation. At the same time, the determination and accounting of higher harmonic currents in traditional thermal models is difficult because existing models are either too simple and cannot take into account HC currents or they are complex and require a significant number of initial conditions to be specified (e.g., finite element analysis). The traditional approach, based on the root mean square values of individual harmonic currents, is difficult to apply due to the difficulty of recognizing harmonics in networks with an isolated neutral. In this paper, the authors propose a new approach to accounting for additional heating, where the basis for the mathematical model of additional cable heating by harmonic currents is proposed to be the use of wavelet analysis, namely, high-frequency range wavelet coefficients. The advantage of the proposed approach is a significant reduction in computational resources. This creates a practical opportunity to use SGF diagnostic features not only to locate damage, but also to quickly assess the thermal condition of the line in real time.
Keywords
single-phase ground fault, higher harmonics, cable heating, wavelet analysis, thermal process simulation
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