The effect of generator loss
First, the power transformer on the impact of the system are:
1, low excitation and loss of the generator, from the system to absorb reactive power, causing the power system voltage drop, if the power system reactive power reserve is insufficient, will make the power system adjacent to some of the voltage below Allow the value, damage the load and the stable operation between the power supply, and even collapse of the power system voltage and collapse.
2, when a generator loss of magnetism, due to voltage drop, the power system of other generators, in the automatic adjustment of the role of excitation device will increase its reactive power output, so that some generators, transformers or lines Over-current, the backup protection may be due to over-flow and malfunction, so that the scope of the spread of the accident.
3, a generator loss of power, due to the generator active power swing, and the system voltage drop, will likely lead to the normal operation between the generator and the system, or between the various parts of the power system out of step, Cause the system to oscillate.
4, the greater the rated capacity of the generator, in the low excitation and loss of magnetic, resulting in the greater the reactive power shortage, the smaller the capacity of the power system, the ability to compensate for this reactive power shortage smaller. Therefore, the greater the ratio of the stand-alone capacity of the generator to the total capacity of the power system, the more serious the adverse effects on the power system.
Second, the generator loss of power on the main impact of the generator itself are:
1, due to the engine after the devastation occurs in the rotor rotor circuit in the differential frequency current, differential frequency current in the rotor circuit in the loss, if beyond the allowable value, will make the rotor overheating. In particular, the direct cooling of the high strength of large units, the heat capacity margin is relatively reduced, the rotor is more likely to overheat. The rotor surface of the differential frequency current, but also may make the rotor body wedge, the ring surface of the contact surface serious serious overheating or even burns.
2, the loss of the generator into the asynchronous operation, the generator of the equivalent reactance reduced from the power system to absorb reactive power, loss of power before the active power, the greater the difference, the smaller the equivalent reactance , The greater the reactive power absorbed. In the heavy load after the loss of magnetic, due to over-current, will make the generator stator overheating.
For the large-scale turbo-generator with direct cooling rate, the maximum value of the average asynchronous torque is small and the inertia constant is relatively reduced. The rotor is also asymmetrical in the vertical and horizontal axes. For these reasons, after heavy load loss of magnetism, this generator torque, active power to the occurrence of severe cyclical swing.
For hydro-generators, a similar situation occurs when the average value of the average asynchronous torque is small and the rotor is asymmetrical with respect to the vertical and horizontal axes and under heavy load.
In this case, the motor torque with a large or even exceeding rated value is periodically applied to the shaft of the generator and transmitted through the stator to the stand. At this point, the slip is also cyclical changes, the maximum value may reach 4% to 5%, the generator periodically severe overspeed. These circumstances, are a direct threat to the safety of the unit.
4, loss of magnetic operation, the end of the stator magnetic flux enhancement, will make the end of the components and the edge of the core overheating.