Dries Putman

Thermal analysis of the influence of nonlinear, unbalanced and asymmetric loads on current conducting capacity of LV-cables

Asymmetry, unbalance and nonlinearity of loads affect the current distribution in both phase and neutral conductor cores in three phase power supply systems. Consequently, temperature distribution in the cable section which is directly related to the power dissipation is influenced. Applying a maximum insulation temperature as boundary condition, the power conducting capacity of LV-cables will substantially be affected by asymmetry, unbalance and especially nonlinearity of loads. The most relevant combinations of asymmetry, unbalance, and nonlinearity were analyzed. The temperature distribution in the cable section is thermally calculated and is subsequently simulated, using 2D finite element modelling. Finally, measurements of the cable temperature arc performed verifying the simulation results.

Modelling and sensitivity analysis of the thermal behaviour of cables for different current conditions

Asymmetry, unbalance and nonlinearity of loads affect the current distribution in both phase and neutral conductor cores in three phase power supply systems. Especially in cases of nonlinear single phase loads the neutral conductor can be loaded with an excessive current. Consequently, cable temperature, which is directly related to the power dissipation, is highly affected. Applying a maximum insulation temperature as boundary condition, the power conducting capacity of LV-cables will substantially be affected by asymmetry, unbalance and especially nonlinearity of loads. Physical cable parameters with respect to both thermal resistance and cable geometry were analyzed in order to determinate the most relevant influencing parameters. The temperature distribution in the cable section is thermally calculated and is subsequently simulated, using 2D finite element modelling. Finally, measurements of the cable temperature are performed verifying the simulation results.

Analysis on the increased losses in supply systems due to voltage drop and voltage distortion

Non linear load currents generate increased losses in supply system elements, such as transformers, cables, capacitor banks, harmonic filters etc. Due to the interaction between these elements through grid impedance and voltage distortion, it is not sufficient to consider the losses in the separate elements to optimise the energy efficiency of the entire supply system. Only the overall energy loss of the supply system is of interest. A simulation tool is developed and used to compare supply system configurations, with respect to total losses.