作业七:将下列段落翻译成中文 Frequency Stability

Frequency stability refers to the ability of a power system to maintain steady frequency following a severe system upset resulting in a significant imbalance between generation and load. It depends on the ability to maintain/restore equilibrium between system generation and load, with minimum unintentional loss of load. Instability that may result occurs in the form of sustained frequency swings leading to tripping of generating units and/or loads. Severe system upsets generally result in large excursions of frequency, power flows, voltage, and other system variables, thereby invoking the actions of processes, controls, and protections that are not modeled in conventional transient stability or voltage stability studies. These processes may be very slow, such as boiler dynamics, or only triggered for extreme system conditions, such as volts/Hertz protection tripping generators. In large interconnected power systems, this type of situation is most commonly associated with conditions following splitting of systems into islands. Stability in this case is a question of whether or not each island will reach a state of operating equilibrium with minimal unintentional loss of load. It is determined by the overall response of the island as evidenced by its mean frequency, rather than relative motion of machines. Generally, frequency stability problems are associated with inadequacies in equipment responses, poor coordination of control and protection equipment, or insufficient generation reserve.

In isolated island systems, frequency stability could be of concern for any disturbance causing a relatively significant loss of load or generation. During frequency excursions, the characteristic times of the processes and devices that are activated will range from fraction of seconds, corresponding to the response of devices such as underfrequency load shedding and generator controls and protections, to several minutes, corresponding to the response of devices such as prime mover energy supply systems and load voltage regulators. Therefore, frequency stability may be a short-term phenomenon

or a long-term phenomenon. During frequency excursions, voltage magnitudes may change significantly, especially for islanding conditions with underfrequency load shedding that unloads the system. Voltage magnitude changes, which may be higher in percentage than frequency changes, affect the load-generation imbalance. High voltage may cause undesirable generator tripping by poorly designed or coordinated loss of excitation relays or volts/Hertz relays. In an overloaded system, low voltage may cause undesirable operation of impedance relays.

频率稳定度

频率稳定度是指一种电力系统,以保持稳定的频率下产生的生成和负载之间的显著不平衡严重系统心烦的能力。这取决于维持/恢复系统生成和负载之间的平衡,带负载最小意外损失的能力。不稳定,可能会导致发生在持续的频率波动导致跳闸生成单元和/或负载的形式。严重系统混乱通常导致频率,功率流,电压,和其他系统变量的大偏移,由此调用的过程,控制和保护未在常规过渡稳定性或电压稳定性研究建模的操作。这些过程可能很慢,如锅炉动力学,或只触发极端系统条件,如伏特/赫兹保护跳闸发电机。在大型互连的电力系统中,这种情况是最常见的以下条件的系

统分裂成岛屿相关联。在这种情况下,稳定是每个岛是否会达到操作平衡状态与负载的最小意外丢失的问题。它是由岛的总响应就证明了它的平均频率,而不是机械的相对运动确定的。一般来说,频率稳定度问题,在设备的反应,控制和保护设备,或不足一代,储备的协调性差的不足有关。

在孤岛系统,频率稳定度可能会关注任何干扰造成一个相对显著损失负荷或产生的。期间的频率偏移,这被激活将范围从几秒钟分数,对应于诸如低频减载和发电机的控制和保护设备的响应,到几分钟的过程和设备的特征时间,对应于装置,例如响应作为原动机的能源供应系统和负载电压调节器。因此,频率稳定性可以是短期的现象,或长期的现象。期间的频率偏移,电压幅值可显著的变化,特别是对孤岛与低频减载的卸载系统的条件。电压大小的变化,这可能会在比例比频率的变化是更高的,影响负载代不平衡。高电压可能会导致不良的发电机励磁通过继电器或伏/赫兹继

电器的设计或缺乏协调的损失跳闸。在一个系统过载,低电压可能导致阻抗继电器的不良操作。