# Electrophysical Method for Identifying the Causes of Excessive Hydro Generator Vibration
## 2 A Brief Review of the Existing Investigations of the Causes of Hydro Generator Vibration  
A large number of studies related to the urgent problem of hydro generator excessive vibration have been analyzed. Highlighted among the literature considered can be [23; 24; 25; 26; 27; 28; 29; 30].  
In [23], the effect of load current harmonics on vibration of three-phase generator is investigated. The results of laboratory experiments conducted show that the load nature strongly determines generator vibration. Higher load is revealed to result in higher generator vibration. Meanwhile, the higher the harmonic content of the load, the higher the vibration of a generator.  
[PERSON] et al. [24] analyzed torsional vibration parameters of a hydro generator set considering the coupling action of hydraulic and electromagnetic excitations. Electromagnetic vibration was investigated in terms of effects of excitation current and internal power angle on the amplitude of hydro generator torsional vibration. A finite element model of shaft system and method of vibration analysis to be applied to design and stable operation of hydro generator sets are proposed.  
In [25], a 3D finite element model of the hydro generator shaft system established using ANSYS software is presented. The model proposed calculates the natural frequency of vibration and the critical speed of rotation. These parameters can be used to determine the dangerous resonance zone. The results obtained could provide a foundation for dynamic analysis and design or improvement of hydro generator set construction.  
The study presented in [26] provides a foundation for guiding the structural design solutions and improvement of the hydro generator shaft system to avoid the resonance caused by external excitation sources, thereby ensuring the safety and stability of the hydro generator set operation. Consideration was given to the internal mechanism of shaft vibrations. Using a finite element model, the natural vibration characteristics and critical rotational speed of the shaft system were calculated. The results obtained formed the basis for the analysis and prediction of the possibility of resonance in hydro generators.  
[PERSON] et al. [27] studied the influence of the imbalanced magnetic pull (UMP) in a three-phase generator under a no-load condition caused by dynamic and static eccentricity of rotor on the rotor vibration.  
[PERSON] et al. [28] studied the correlation between vibration of generator guide bearings and magnetic imbalance of hydro generators. A method of magnetic monitoring that involves measuring the magnetic flux in the air gap in hydro generators was applied.  
The research described in [29] consists in vibration analysis of a hydro generator that equips a Kaplan hydraulic turbine installed at a hydroelectric power plant in Romania. The results of vibration measurement for a no-load condition (without excitation and with excitation) and under-load condition are presented, with the measurement being conducted both before and after the hydro generator repair. An analysis of the influence of rotor magnetization state and hydraulic factors on the hydro generator vibration based on the experimental data obtained was performed.  
In [30], the effect of hydraulic vibration on the stability of operation and service life of hydro generator sets was examined. To investigate nonlinear dynamic characteristics of the hydro generator resulting from hydraulic vibration, a nonlinear mathematical model of the hydro generator set was established using Lagrange equations.  
These studies [23; 24; 25; 26; 27; 28; 29; 30] described hydraulic, dynamic and magnetic effects on hydro generators. Our research was performed on an operating network on identification of the root causes of electrophysical effect on hydro generators, which defines its originality.