# Electrophysical Method for Identifying the Causes of Excessive Hydro Generator Vibration
## 5 Conclusions  
In this research, the recording of electrical energy parameters, power quality indices and the calculation of vibration forces were carried out to investigate electrophysical effects on hydro generators. The following conclusions can be deduced from the results obtained.  
1. In the power supply scheme of the aluminum smelter, the powerful nonlinear load of the enterprise impacts negatively on the operation modes of the HPP-I power equipment in consequence of the distortion of currents and voltages in the 10 kV  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Parameters** & **Symbol** & **Value, \(\upmu\)m** \\ \hline \multirow{3}{*}{Torsional vibration} & Amplitude of the tangential core displacement caused by the ULF current component & \(2W_{1}\) & 4.8–8.3 \\  & Tangential core displacement amplitude at surge currents & \(2W_{1}\) & 95.2–117.0 \\ \hline \multirow{3}{*}{Radial vibration} & Core vibration caused by the ULF current components & \(2U_{1}\) & 2.8–3.2 \\  & Core shock vibration & \(2U_{1}\) & 28.8–35.0 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Vibration parameters of the elements of the 38.5 MW SV-655/110-32 hydro generator when the ULF current component and surge currents are superimposed.  
busbars of the hydropower plant. Periodic routine testing of the HPP-I generators detected an increased level of stator core and upper-bracket vibration and increased level of shaft runout. This study has proved that this occurs when emerged in the generators are significant torsional and radial forces caused by the nonlinear load of the AS. The G-3 and G-4 generators operating through the F-6 busbar have the highest values of oscillation and vibration.
2. The effect of current impacts of the load of the smelter on the HPP-I hydro generators was analyzed by torsional forces, and tangential vibration emerged in the hydro generators' evaluation. The superimposition of negative sequence currents is shown to be a consequence of the load imbalance.
3. The tangential forces of double frequency (100 Hz) do not produce significant vibration displacement when the imbalance factor is less than 2%. The increase in the amplitude of the natural vibration of the basket-type end-winding parts occurs at natural frequency below 100 Hz. For instance, at a natural frequency of 86 Hz, the maximum oscillation reaches 80 \(\upmu\)m. When the tangential torsional vibration of the core is excited beyond the resonance frequency range, the vibration values are low, within 2 \(\upmu\)m.
4. The superimposition of the ultralow-frequency current component results in a slight increase in vibration up to 3 \(\upmu\)m in the radial direction and up to 8 \(\upmu\)m in the tangential one. In this case, a shift in the mechanical impact frequency, appearance of side frequencies, and increased danger of their falling into the near-resonance zone are observed. The values of vibration and surge displacement increase significantly under near-resonance conditions.
5. The cause of increased vibration noted during inspection and repair tests was identified. The study has shown that the surge current superimposition has a short-term nature, with the value of the vibration displacement exceeding the acceptable level. Such impacts have an intense nature, causing reduction in the hydraulic turbine service life and the need for more frequent repairs.  
Conceptualization, A.S.K., V.V.Y., G.P.F. and E.I.G.; Formal analysis, A.S.K., V.V.Y., G.P.F. and E.I.G.; Investigation, A.S.K., V.V.Y., G.P.F. and E.I.G.; Writing--original draft, A.S.K., V.V.Y., G.P.F. and E.I.G.; Writing--review & editing, A.S.K., V.V.Y., G.P.F. and E.I.G. All authors contributed equally to the study conception and design. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data are not publicly available due to trade-secret protection.  
The authors declare no conflict of interest.