Exciting system of generator-motors of Zagorsk pumped-storage station: Adjustment and operating experience

Abstract

Exciting systems of synchronous hydraulic-turbine generators, unlike the main equipment of hydroelectric stations (generators, turbines), are modified rather quickly, including during operation. This is possible due to the rapid interchangeability of the generations of electrical (electronic) elements composing the systems and also because modernization is possible in stages, without interrupting the operation of the main equipment.Therefore a detailed analysis of the hardware of an exciting system developed more than 15 years ago is hardly relevant. Nevertheless, a number of fundamental principles are of interest even today, since the positive solution of certain problems requires changes in the design and construction of the system, which should be taken into account when planning new stations.At the Zagorsk pumped-storage station (PSS) exciting systems of type STSA-300-2000-2.5 with automatic excitation regulators of type ARV-SDP1-21 are installed on all generator-motors. The development, design, and manufacture of the system were carried out by the All-Russian Electrical Machine Construction Research Institute (VNIIl~lektromash) (St. Petersburg) and research-production association Ural61ektrotyazhmash (Ural Heavy Electrical Machinery Plant).Two variants were compared when developing the system --with natural air and water cooling of the thyristors. Since neither one of the variants had explicit economic and technical advantages, the circumstances that thyristor starters with natural air cooling of the thyristors and, furthermore, distilled water is not used either for cooling the generator-motors, i.e., its sufficiently productive source (generator) is absent at the station, were already provided for at the station were taken into account. Therefore the final decision when selecting the design of the converters was made in behalf of natural air cooling.The exciting system provides a standard set of regimes and exciting parameters of the generator-motor in a generator regime and synchronous capacitor regime, and, furthermore, starting in a pump regime (direct asynchronous from the static frequency converter) and electrodynamic braking during stopping of the unit (Table 1).In the case of failure of two parallel branches in any of the arms of the converter or in the case of failure of one branch in each of like arms of both converters during their joint operation as well as in the case of the operation of only one converter with a full number of rectifiers, an exciting current of not more than t250 A is allowed, which is sufficient for operation of the unit in a generator regime. However, a pump regime of the unit in this situation is impermissible.A basic circuit diagram of the exciting system of the generator-motors of the Zagorsk PSS is shown in Fig. 1. The thyristor converters are connected through a converter (rectifier) transformer (RT) to leads of the lowest voltage of the stepup (block) transformer. Such a connection of the rectifier transformer permits starting the reversible unit without an additional ...