Analysis of impact of distributed capacitance in stator windings of large hydroelectric generators on displacement voltage

The centralized parameter circuit model cannot address the issue of excessive neutral point dis‑ placement voltage in Jinghong generators when the three-phase potentials are symmetrical and the static measured three-phase-to-ground capacitances are approximately equal. Therefore，a neutral point displace‑ ment voltage analysis method based on the quasi-distributed capacitance parameter model is proposed. By circuit analysis，the relationship formula between the stator winding quasi-distributed capacitance to ground and the neutral point displacement voltage is obtained. Through theoretical analysis，it is verified that nonuniform distributed capacitance leads to the appearance of displacement voltage. Experimental validation is conducted by using a 12 kW dynamic simulation generator manufactured by Lanzhou Electric Machinery Factory. Quantitative analysis is then carried out on the experimental results regarding the impact of the positions of larger or smaller quasi-distributed capacitance and quasi-distributed capacitance unevenness on displacement voltage. In response to the issue of excessive displacement voltage caused by non-uniform dis‑ tributed capacitance，a solution involving the addition of external capacitance at the machine end is proposed and the external capacitance value is theoretically calculated. The effectiveness of the retrofit solution is verified through simulation experiments. © 2024 Electric Power Automation Equipment Press. All rights reserved.