Power system consist of elements which operate in the linear range of operation,
even though they are nonlinear. The non-linearity in the system most often represent
transformers due to its own magnetic saturation. The network is due to nonlinearities
occurring harmonics. The network element comes to the flow of magnetization,
which is growing rapidly and contains higher harmonics. Higher harmonics and rapid
flow also mean a higher voltage. A typical example, which is generated due to
saturation of the elements and cause overvoltages is ferroresonance.
Ferroresonance is a complex and complicated phenomenon, but due to its unique
impact on the network, interesting to study and analyze. It occurs in the presence of
non-linear inductance and capacitance, which is absolutely necessary to be in a
certain ratio.
In the first part of the diploma thesis the conditions, which are necessary for the
emergence of the ferroresonance phenomenon and for sharing the phenomenon on
parallel and serial ferroresonance, are described in detail.
The first part of a thesis also describes the parameters of the components and initial
conditions of the system which affects the actual phenomenon. Ferroresonance
recognize the type fluctuations, which is characterized by four different shapes of
oscillation modes. These are fundamental, subharmonic, quasi-periodic and chaotic
shape.
The consequences of the ferroresonance phenomenon can be catastrophic, as these
lead to various failures, internal equipment of the system is in danger and the staff as well. Therefore, the phenomenon should be understood, recognized in certain
situations and prevented or limited. The various methods are used which restrict or
completely eliminate the phenomenon. For this purpose are used computer
simulation methods, for example, a method of the spectral density, Poincaré map,
phase plane etc, which by means of simulation programs provide a solution and the
necessary data for a corresponding appropriate protection of the system.
In the second part of the thesis a simulation of the ferroresonance phenomenon on
the real network in the area of integrated economic complex (ZGK) Ravne was
conducted. For the previously mentioned simulation the computer simulation
program PSCAD (Power System Computer Aided Design) was used. The network
consists of key elements, necessary for the formation of ferroresonance. These
elements are underground cable line, a voltage transofrmer (VT) and the voltage
source. The simulation is based on the graphic display of (over)voltages and currents
in the individual elements of the fundamental frequency. The solutions are analyzed
in a three-phase circuit, in which the ferroresonance occurred. With certain
parameters are researched basic features of ferroresonance phenomenon. In this
context, due to missing, certain data of individual elements are customized to the
occurrence of the condition, described in the theoretical part of a diploma thesis.
Based on the results we came to the conclusion, which actually comply the relevant
conditions for the emergence of ferroresonance.
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