Three-phase and single-phase measurement of overhead power line capacitance evaluation

Accurate electrical parameters of the overhead power lines are essential inputs for industry (protection relays settings, power flow calculations, grid stability estimation) and scientific studies (simulation models in general). While impedance measurements of overhead power lines are common today, capacitance measurements are mostly insufficiently documented and examined. The impedance of the power line was covered by the authors’ collective in their previous work. In contrast, the capacitance of the power line estimated by the standard offline measurement is discussed in detail in this paper. Capacitance measurement on actual extra-high-voltage (EHV) overhead power lines is compared with the simulation of such measurement and the typical capacitance of overhead power lines computations. The shunt capacitance theory is explained in detail, transforming from the phase quantities to the symmetrical components. The measurement apparatus is described, together with the safety precautions essential to assess and maintain. Step-by-step capacitance estimation from the actual measured quantities is introduced in detail. In conclusion, the simulation and the physical measurement results were nearly identical, and the comparison with the calculation showed some minor discrepancies, which are also discussed. This article, therefore, represents a comparison of unique actual measurement data obtained using different methodologies compared to the very detailed simulation model, which is nearly non-existent in the current academic papers. Furthermore, the measurement methods M1 and M2 are the authors’ original addition to existing methodologies.