# Multi-Domain Modeling and Analysis of Marine Steam Power System Based on Digital Twin
## 5 Fault Simulation Analysis of Marine Steam Power System Based on Digital Model
(1) Failure of water level regulation  
The regulation of the water levels in the condenser and deaerator, which plays an important role in the safe and stable operation of the condensate feed water system, mainly involves the marine condensate feed water system. If the water level in the condenser is too high, the cooling effect will be weakened and the vacuum degree of the unit will drop, and, if the water level is too low, cavitation of the condensate pump will occur, affecting the safety of the unit. Too high a water level in the deaerator will cause unstable pressure in the deaerator and affect the deaerating effect. Too low a water level will reduce the inlet pressure of the feed pump and cause cavitation of the pump, which will damage the feed pump in serious cases. Figure 24: Fault diagnosis process of marine power system based on digital model. Therefore, based on the digital model, a fault simulation study is carried out on the water level regulation failure of the condensate feed water system, and a quantitative analysis is made on the change rule of the main parameters of the system caused by the water level regulation failure. The influence of water level regulation failure on the main state parameters of the condensate feed water system is shown in Figures 25-28. Figure 27: The water level of condenser under normal and failure of water level regulation. Figure 26: The condenser pressure under normal and failure of water level regulation. Figure 25: The steam turbine output power under normal and failure of water level regulation. Through a quantitative simulation study of the failure of water level regulation in the condensate feed water system, it can be seen that, when the water level regulation is sluggish, the water level in the condenser and deaerator fluctuates continuously, thus causing the fluctuation of the condenser pressure and the turbine output power. If the water level regulation is sluggish for a longer time, or even fails, the safety and stability of the condensate feed water system will be greatly affected. Therefore, attention must be paid to water level regulation during steam turbine operation to avoid failure. (2) Air leakage of the condenser vacuum system  
During the operation of the condenser, air will inevitably leak in. It is precisely because the air extractor can draw out non-condensable gas from the condenser that the condenser can maintain a good vacuum. When the working state of the air extractor remains unchanged and the amount of air leaking in increases, the proportion of air in the condenser will increase. In order to analyze the influence of different amounts of air leakage into the condenser on the condenser, take a 70% working condition as an example, assume that other input and output variables of the system remain unchanged, and simulate and analyze the changes of the main operating state parameters of the condenser when the air leakage increases from 10% to 60%. The influence of the increased air leakage on the main state parameters of the condenser is shown in Table 6.  
According to the state parameters of the condenser, the relationship curves between the pressure increment of the condenser, the temperature increment of the circulating cooling water and the increase proportion of the air leakage are drawn as shown in Figures 29 and 30. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Increase Proportion of Air** & **Condenser Pressure** & **Temperature Rise Increment** \\
**Leakage (\%)** & **Increment (Bar)** & **of Cooling Water (\({}^{\circ}\)C)** \\ \hline
10 & 0.011 & \(-0.11\) \\
20 & 0.023 & \(-0.23\) \\
30 & 0.035 & \(-0.42\) \\
40 & 0.052 & \(-0.71\) \\
50 & 0.076 & \(-1.05\) \\
60 & 0.113 & \(-1.38\) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Influence of increased air leakage on main state parameters of condenser. Figure 28: The water level of deaerator under normal and failure of water level regulation.