励磁控制对输电保护载荷能力的影响

Effect of Field Control on Transmission Relay Loadability

输电载荷能力包括热载荷和保护载荷约束。低压重载系统中,保护载荷度可能取代热载荷度,导致保护不合理动作以及后续连锁过程。提出输电保护载荷能力和机组励磁电流的灵敏度模型,量化电压下降过程中励磁控制对输电安全约束的影响。研究结果表明:发电机过励控制与其电压定值有关;过励和强励控制下,过负荷和低阻抗保护可能过高或过低估计热载荷能力;事故过程中,保护载荷度可能与后备保护方案和保护定值有关。

Transmission loadability includes the thermal and the protective constraints. In case of low voltage and heavy load, the relay loadability may replace the thermal loadability, leading to undesirable relay operation and cascading events. A sensitivity model between the transmission loadability and the field control of generators is newly proposed, thus to quantify the security margins under field control during voltage depression. The numerical results show that the generator overexcitation control depends on its voltage setting; the overload and the underimpedance constraints may underestimate or overestimate the thermal loadability under voltage depression; the relay loadability depends on not only the protection schemes, but also the relay settings.