外文翻译--大型发电机干扰下发电机保护的性能
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1、English Material: Performance of Generator Protection During Major System Disturbance Abstract: Disturbance is an inherent part of easy power system during the transition from one steady-state operating condition to the next. Protective relays may experience abnormal operating conditions during this
2、 transient period. This paper reviews control actions drat play a part during the transition and provides technical guidance to the industry on the application and setting of generator protective relays that can operate during major system disturbances. Index Terms: AC generator excitation、 ac gener
3、ator protection、 governors、 power system control turbines. .INTRODUCTION: Every power system is subject from time to time to transient disturbances primarily due to faults and/or switching of major load. Normally, the system adapts to a new steady-state condition with the help of generator excitatio
4、n and turbine governor control systems. A variety of additional power system control schemes may also be used to help restore an acceptable new steady-state condition. One of the lessons learned from the past major disturbances is that some of the functions associated with generator protection may o
5、perate during these transient conditions. It is important for the relays to provide protection while optimizing their coordination to avoid undesirable operation during the system disturbances and thereby help preserve the integrity of the power grid. Brief descriptions of past power system disturba
6、nces as well as generator excitation, turbine governor, and power system controls are included in this paper. The balance of the paper discusses the generator protection functions that may operate during system disturbances. . POWER SYSTEM DISTURBANCES: Power system disturbances are events that prod
7、uce abnormal system conditions and the state of the system may change from normal to emergency. These disturbances can be classified into two groups-small and large. Large disturbances are a challenging problem for the utilities because of the size and complexity of the power system. Adequate protec
8、tion and control actions are required after a system disturbance to prevent further degradation of the system and restoration to the normal state. Many system disturbances can be attributed to tight operating margins and less redundancy in generation, transmission, and distribution capability. These
9、 are best addressed at the planning stage. A properly designed system is less vulnerable to large-scale disturbances. However, small disturbances cannot be eliminated due to the physical nature of the system. Overhead lines constitute a significant component of any power system and experience freque
10、nt faults that are caused by variety of reasons. Stable operation of a power system requires a continuous matching between energy supply to the prime movers and the electrical load on the system and an adequate reactive power support mechanism to maintain voltage within limits at different buses. Th
11、ese conditions are not satisfied during faults and other disturbances. During a fault, the terminal voltage dips and power transfer through the faulted system are altered depending on, the type of fault. After successful clearing of the fault, the system adapts to a new steady-state condition. If th
12、e fault is not cleared before the critical fault clearing time, system instability will occur. Even the successful clearing of faults may sometimes lead to undesired relay operations because of line overloads, inadequate reactive power support, and an improper relay setting. These may, in turn, deve
13、lop into large system disturbances due to cascading. Disoperation of relays may result in undesired and/or sympathy tripping leading to large system disturbances. Inadequate protection arrangements, such as the absence of bus-bar protection for critical system buses, may also result in system distur
14、bances due to song fault clearing time by remote back-up protection. Loss of a large generator or a large block of load changes the system frequency and may alter the reactive power flow in the network. This requires control action, like under frequency load shedding, to restore the system frequency
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