Relay Protection Setting Calculation And Analysis Of Large Hydropower Station And High Voltage Power Network

With the power system's development, there are several construction projects of large and even oversize hydropower stations, and the safe operation issue in such stations catches more and more attention. In order to ensure the stable operation of the stations and the power system, the service power systems become more and more complicated, which sets new problems for the relative relay protections and their setting calculation. On the other side, the widely application of double-circuit line brings higher requirements about the setting calculation work. Taking service power system of large hydropower station and high voltage power network as research objects and integrating two practice projects, this paper has finished the setting calculation work and analyzed the particular problems, meanwhile has put up some methods useful in practical operation.At first, analyze the characteristics of service power system of large hydropower station and its relay protections. To ensure the power supply reliability of the large hydropower station, its service power system takes several power sources for mutual backup and complex network, for example there are generator, source out of the station and appropriative source station in the Three George Right Bank Power Station, which forms a small supply network comprising several supply voltage levels and crossed loop networks. Complicated network structure requires more kinds of protections to guarantee the operation safety of the power station, which makes the protections and their coordination complex, and meanwhile brings much more problems for the setting calculation work.On the basis of analyzing and summarizing the characteristics of the Three George Right Bank Hydropower Station, this paper built up a simulation-model, according to the practice conditions of the power station, to calculate kinds of fault current and finished the setting work for protection devices of the middle and high voltage levels in the service power system. All of these works follow operation requirements of the power station. This paper analyzed the specific problems of setting works, and at last put up with some useful solutions. Now, the settings have been applied into the real operation and make sure the first generator's successful running.Double-circuit line has widely applied in the high voltage power network to satisfy the demands of long-distance and high capacity power transmission and large power grid development. But the zero sequence mutual impedance between circuit lines make the protection equipments take malfunction or reject to act when they should. Starting with the characteristics of double-circuit line when faults happen, integrating with zero sequence network, the paper analyzed the influences to zero sequence component, pilot protection and ground distance protection, especially the influence to measuring impedance of ground distance protection. And then compared and analyzed three popular setting calculation methods for ground distance protection, and discussed their advantages, disadvantages and applicability. In the base of analysis, proposed a feasible setting calculation scheme for a high voltage power network of a foreign country, the settings have been applied in the practical running and can satisfy the operation demands.