# Verification Methodology for Simulation Models of the Synchronous Generator on Transients Analysis
## 1 Introduction
Ongoing research confirms that it is important to analyze generator parameters in the event of a sudden short-circuit. In [9], subtransient reactances and time constants are calculated by both analytical and finite-element methods, and applied to the classical circuit-theory simulation of a short-circuit fault. The terminal reactance parameters during the transient process were obtained using a 2D finite element analysis and validated by experimental results in [10]. Transient torques that appeared during faulty synchronization were observed in [11], and the physical quantities existing during faulty synchronization were compared with a three-phase sudden short-circuit state. From this comparison, the values of physical quantities that should be taken into account during the design of new hydro generators were selected. There are other interesting studies regarding transient modeling, such as [12], which deals with the transient modeling of thermoelectric modules as power generators and [13], which deals with the transient simulation of a combined system consisting of internal combustion engines and the organic Rankine cycle (ICE-ORC) designed in MATLAB/Simulink. Many studies are engaged in the development of models that allow monitoring of generator behavior, especially during transients. In [14], the authors present the transverse magnetomotive force (m.m.f.) distribution model, and the calculated results are validated by the FEM and measurements. The multi-loop model of fractional pole-path ratio synchronous generators is proposed in [15], and comparisons of simulation results are again made by the FEM. The linear saturated lumped magnetic parametric model is developed to exhibit magnetic characteristics of a line-start permanent magnet synchronous motor, as proposed in [16]. The evaluation of analytical model validity is verified using a 2D FEM. In [17], the field-circuit coupled finite-element method is applied to predict the performance of an induction motor by solving the nonlinear time-stepping finite-element equations, coupled with circuit equations and mechanical motion equations. The research described in [18] is focused on the transient analysis of the electromagnetic and temperature fields on tubular hydro-generators during short-circuit faults. Testing and fine-tuning of the developed dynamic mathematical model of the hydropower plant, for research into the dynamic conditions of a transmission power system, are described in [19]. In the models presented here, the researchers successfully solved the problem of transients, but mostly in isolated cases of electrical machines on a network. However, if the impact on the wider parts of a power system, with all installed elements, is to be considered, then each element of the system must be presented with equivalent parameters. Then, the transients are solved by applying a system of differential equations, for which special software packages have been developed. Such a methodology is very practical and fast, but the accuracy of the obtained results depends on the accuracy of the equivalent parameters. The FEM is the most suitable method for calculating equivalent parameters, because testing procedures for extracting equivalent parameters often cannot be performed in real conditions. The research presented here refers to the methodology for verifying the accuracy of a fast simulation method by comparison with a more accurate method. In this paper, results are presented for the simulation of a sudden three-phase short-circuit of a hydro generator, using the FEM for the calculation of the model's magnetic field, which corresponds to an actual state. By using the FEM to calculate the magnetic field in electrical machines, it is possible to determine the actual values of electrical parameters, as this research indicates. The electromagnetic transients are also analyzed by simulating a three-phase short-circuit at the generator terminals on a simulation model that uses dynamic models of elements, such as actual hydropower plants connected to the distribution network.