Abstract: The power plant generator serves as the emergency power supply to deal with frequently and to the electrical network unit, the generating plant breakdown, the equipment overhaul.When the electrical network breaks down unit, the emergency generator should start in the shortest time, transports the qualified electrical energy to the electrical network, provides the power source for the current collector, simultaneously separates the main switch which the breakdown unit and the electrical network connect.Compound is the extremely important operation, the generator non-same time compound, can produce the very big surge current, not only can endanger unit own security, but also can cause the electrical network to have the undulation, the destruction stability.Therefore request same time equipment and control, protective device complete reliable