Hierarchical hybrid neuro-fuzzy framework for predictive thermal behaviour analysis of underground electrical cables under soil moisture and load variability
摘要
An adequate model of predicting the thermal behaviour of underground power cable systems is needed to prevent insulation failure and maximize current-carrying capacity (ampacity). The existing approach is spatial, whether it is through computationally intensive physics-based models that cannot be operated in real time to track data, or data-based surrogates that take the soil to be a stationary medium that neglects the influence of moisture-sensitive conductivity, cyclic thermal charging, and convection processes. A hierarchical hybrid neuro-fuzzy model with three integrated steps, (A) PSO-optimized ANFIS soil thermal-state estimator in the format of predicting effective soil thermal conductivity as a factor of geotechnical properties, is presented in this paper; (B) GA-optimized ANFIS cable transient thermal predictor, which uses the output of Stage A predictors to predict the temperature of the conductor, sheath, and thermal charging rate, and regularized by a physics-informed loss criterion based on the transient heat conduction equation; and three data sets are used: a 257 case database of soil thermal conductivity to be used in the Stage A calibration, 7560 FEM-simulated cable conditions under the dry, moist, and wet soil regime to be used in the Stage B training, and published experimental benchmarks to be used to independently validate those experiments. The mean RMSE of the proposed framework is 0.92 ± 0.04 °C and a mean R2 of 0.983 ± 0.002 on heldout test data which is better than plain ANFIS (RMSE 1.85 ± 0.08 °C), ANN-BP (RMSE 1.45 ± 0.06 °C) and IEC 60287 solutions (RMSE 4.31 °C). Ablation analysis reveals ability to reduce RMSE by 40.0% with optimization by PSO-GA, physics-informed loss by 14.6%, and the hierarchical cable coupling of soils by 5.3%. The inference latency of an average workstation (9.4 ms) means that it can be used with real-time dynamic thermal rating systems. It is, as far as we know, the first hierarchical neuro-fuzzy structure, which jointly develops the estimation of the moisture-sensitive soil thermal state and the transient cable thermal prediction, under variable, cyclic loading, through physics-based regularization and interpretable fuzzy decision support.