Overvoltages and power oscillations in hydro generators

The paper describes two specific transient phenomena of different characteristic frequencies. First, a short overview of a calculation of overvoltages in the generator main electrical circuit of a hydro power station is presented. A case of a generator connected to the step-up transformer through encapsulated lines has been studied. The most critical cases have been considered: overvoltages at a single phase earth fault in the generator circuit and temporary overvoltages due to the single phase earth fault followed by the load rejection. The calculations have been carried out by EMTP-ATP and MicroTran program. Second, electric power oscillations in hydro power plants are not rare. The paper shows two cases in two different power plants. Each power plant has different generator positions (one vertical and one horizontal bulb type) and therefore different reasons for power oscillations. An overview of those cases is presented supported by measurements and calculated by Matlab.