阻尼井+变顶高尾水洞是一种新型的水电站尾水压力管道体型,国内尚无单机容量700 MW巨型机组的运行实践经验。为进一步了解大型机组变顶高尾水系统的水力特性,验证工程设计和水工模型试验成果,确保工程安全稳定运行,结合启动试运行和正常蓄水位机组调试安排,对三峡地下电站进行了2个特征库水位(152.3 m,175.0 m)和4个负荷量级(25%,50%,75%,100%)的机组甩负荷水力过渡过程进行现场监测。重点监测了蜗壳和尾水管进口部位水锤压力、阻尼井涌浪、变顶高尾水洞明满流交替和机组转速升高值等内容。监测成果表明:三峡地下电站变顶高尾水洞各项水力参数指标均满足设计要求,并有一定安全裕度,监测成果可为今后变顶高尾水洞工程设计和运行提供参考。

Damping well combined with tailrace tunnel with sloping ceiling is a new type of hydropower station’s tail pipeline. There is no such operation experience for large generation units with unit capacity of 700MW in China. To learn more about the hydraulic characteristics of tailrace system with sloping ceiling of large unit, and to validate the project design and the hydraulic model test results and to ensure the safe and stable operation of the project, we conducted field monitoring on the hydraulic transition process of load rejection of TGP’s underground power station in conditions of two characteristic reservoir water levels (trial run152.3m, normal storage 175.0m) and four load magnitudes (25%, 50%, 75%, 100%). The monitoring is focused on water hammer pressure of spiral case’s end parts and tail pipe’s inlet parts, damping well surge, unsteady free-surface pressurized flow of the tail pipe, and the increment of unit rotating speed. Analysis on the monitoring results suggests that the hydraulic indicators of the tail pipe meet the design requirement, with a certain safety margin. The monitoring results could be reliable basis for the design and project operation of tail pipe in the future.