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福建电网水电机组占总装机容量的59%,并且较集中于电网的闽北片,这些机组多数采用自并励方式。当电网发生短路故障且不能快速切除时,使距故障点电气距离小于临界外电抗的机组因励磁电流的衰减而处于低励或部分失磁状态。在电网故障消失后,由于自并励机的电压恢复特性与失磁保护时间的整定配合问题,使失磁保护动作。导致系统在暂态过程失去大量的电源。本文根据自并励机的短路及电压恢复特性和发电机失磁保护原理对系统低电压状态下失磁保护动作行为进行分析,提出防范措施,以提高福建电网在暂态过程的稳定性。
Hydropower units of Fujian Power Grid accounted for 59% of the total installed capacity, and more concentrated in the northern Fujian section of the grid, most of these units using self-shunt method. When the grid short-circuit fault and can not be quickly removed, so that the electrical distance from the fault point is less than the critical external reactance of the excitation current decay and at low excitation or partial loss of state. After the disappearance of the grid fault, the demagnetization protection is activated due to the voltage recovery characteristic of the self-shunting machine and the setting coordination of the demagnetization protection time. Resulting in the system in the transient process of losing a lot of power. In this paper, according to the short circuit and voltage recovery characteristics of self-shunting machine and the principle of generator loss protection, the action of loss-of-field protection under low voltage is analyzed and preventive measures are put forward to improve the stability of Fujian power grid in transient process.