## 4 Analysis of Transmission Path of Hydropower House
### Transmission Path Identification
#### 4.2.6 Results  
The information-transmission rate between the main measurement points under three conditions is summarized in Table 7. Through the comparative analysis of the transfer-entropy curve and the information-transmission rate of the three working conditions in Table 7, the following conclusions can be drawn:  
1. Taking the calculation results of transfer entropy and the information-transmission rate of the start-up operation condition as an example to analyze the vibration form of the hydropower house, under the start-up operation condition, the information-transmission rate between the top cover and the lower frame foundation is 94.86%, and that from the top cover to the stator foundation is 91.54%, indicating that a larger part of the energy of the top cover is transferred to the turbine pier. The information-transmission rate from the stator foundation to the generator floor is 32.85%, and the information-transmission rate from the lower frame foundation to the generator floor is 32.78%, indicating that the vibration-transfer strength of the turbine pier and the generator floor is smaller than that of the top cover and the turbine pier. Considering the internal structure of the hydropower station, it is presumed that the main reason for reducing the vibration transfer effect is the energy dissipation and vibration reduction effect of the concrete structure.
2. The stator foundation measurement point and the lower frame foundation measurement point together characterize the vibration of the turbine pier, and the top cover characterizes the vibration of the tailwater pipe. Under different working conditions, the transmission path of vibration caused by tailwater fluctuation between each measurement point is unchanged, indicating that the change in the operating state of the hydropower station unit does not affect the transmission direction of vibration signal. According to the transfer-entropy curve and information-transmission rate between different measurement points, the transmission law of tailwater fluctuation vibration is judged as follows: tailwater pipe (top cover measurement point)\(\rightarrow\)turbine pier (stator foundation measurement point, lower frame foundation measurement point)\(\rightarrow\)generator floor (generator floor measurement point).
3. The lower frame foundation is an important support structure of the hydropower house, and the maximum information-transmission rate can be obtained between the top cover and the lower frame foundation under different working conditions,  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Transmission** \\ **Direction** \\ \end{tabular} } & top & \begin{tabular}{c} top \\ cover\(\rightarrow\)stator \\ foundation \\ \end{tabular} & \begin{tabular}{c} top cover\(\rightarrow\)lower \\ floor \\ \end{tabular} & \begin{tabular}{c} top \\ cover\(\rightarrow\)generator \\ floor \\ \end{tabular} & \begin{tabular}{c} stator \\ foundation\(\rightarrow\)lower \\ frame foundation \\ \end{tabular} & \
\begin{tabular}{c} stator \\ foundation\(\rightarrow\)generator \\ floor \\ \end{tabular} &
\begin{tabular}{c} lower \\ floor \\ \end{tabular} \\ \hline
**ITR/\%** & 71.67 & 72.99 & 65.23 & 4.04 & 47.62 & 29.97 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Information-transmission rate between measurement points of condition 3.  
indicating that the lower frame foundation is the main node of tailwater-fluctuation transmission in the hydropower house.  
Figure 16: Transfer-entropy curve between measurement points of condition 3. (**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.