## 4 Analysis of Transmission Path of Hydropower House
### Transmission Path Identification
#### 4.2.2 Operating Characteristic Information Extraction
From Figure 14a and Table 4, it can be observed that the transfer entropy from the top cover to the stator foundation is larger than that from the stator foundation to the top cover and the information-transmission rate is 91.54%, which means that a large amount of information flows from the top cover to the stator foundation, thus judging that the vibration-transmission direction is top cover\(\rightarrow\)stator foundation; Similarly, from Figure 14b,c,e,f, it can be judged that the transfer directions of information are: top cover\(\rightarrow\)stator foundation, top cover\(\rightarrow\)lower frame foundation, stator foundation\(\rightarrow\)generator layer floor, lower frame foundation\(\rightarrow\)generator floor. The transfer entropy between the stator foundation and lower frame foundation measurement points in Figure 14d are close, the two transfer-entropy curves are staggered and the information-transmission rate is 9.35%, which means that there is no obvious one-way information effect between the two measurement points, so the information-transmission direction between the stator foundation and the lower frame foundation can be disregarded. 2.4 Analysis of Vibration-Transmission Path under Stable Operation Condition of Hydropower Station Units  
The transfer-entropy curve of the water fluctuation signal at each measurement point under the stable operation condition of the hydropower station unit are shown in Figure 12.0 The information-transmission rate between different measurement points are shown in Figure 12.1  
Comparing Figure 14 with Figure 15, it can be found that although the transfer-entropy curve under the start-up operation condition shows an obvious rising trend and the transfer-entropy curve under the stable operation condition shows a fluctuating trend, the vibration-transmission direction between the measurement points of the two conditions is identical, indicating that the vibration form of the hydropower house has not changed, and the vibration transfer directions are top cover\(\rightarrow\)stator foundation, top cover\(\rightarrow\)lower frame foundation, stator foundation\(\rightarrow\)generator layer floor, lower frame foundation\(\rightarrow\)generator floor. Comparing Tables 4 and 5, it can be found that the information-transmission rate of stator foundation\(\rightarrow\)generator floor and lower frame foundation\(\rightarrow\)generator floor under the stable operation condition is greater than the start-up condition, which indicates that the vibration caused by the fluctuation of the tail water during the stable operation of hydropower station units has a greater impact on the upper structure of the hydropower house. Figure 12.2 Transfer-entropy curve between measurement points of condition 2. (**a**) Transfer-entropy curve of top cover and stator foundation; (**b**) Transfer-entropy curve of top cover and lower frame foundation; (**c**) Transfer-entropy curve of top cover and generator floor; (**d**) Transfer-entropy curve of stator foundation and lower frame foundation; (**e**) Transfer-entropy curve of lower frame foundation and generator floor; (**f**) Transfer-entropy curve of lower frame foundation and generator floor. As shown in Figure 16, under the shut-down condition, the transfer entropy between the measurement points decreases continuously, indicating that the information-transfer effect between the measurement points is weakening, but the transmission direction of vibration remains unchanged, and the transmission paths of the vibration are still top cover\(\rightarrow\)stator foundation, top cover\(\rightarrow\)lower frame foundation, stator foundation\(\rightarrow\)generator layer floor, lower frame foundation\(\rightarrow\)generator floor. From Table 6, we can find that the information-transmission rate of top cover\(\rightarrow\)stator foundation is 71.67%, and the information-transmission rate of top cover\(\rightarrow\)lower frame foundation is 72.99%, which means that a large amount of vibration energy is transferred from the top cover.