Abstract
The object of research is the equivalent circuit of an impulse current generator designed for testing surge arresters. Calculation of the impulse current generator parameters when discharging a capacitor bank to a complex nonlinear load is a difficult task for an analytical solution. Until now, the application of surge arrester frequency-dependent models was limited to the problems of overvoltage computation. Surge arrester frequency-dependent models can predict the residual voltage with high accuracy. This is the reason to consider that surge arrester frequency-dependent models can be used for calculating the main parameters of impulse current generators designed for physical testing of surge arresters.
 The task of determining the equivalent circuit parameters required for getting a discharge current of a given waveform and amplitude in an impulse current generator scheme with a nonlinear load was solved using circuit simulation.
 This article presents the results of studying the processes in impulse current generator equivalent circuit. In the circuit a dynamic model of a surge arrester is used as the load model. For this, an equivalent circuit for the discharge path of the impulse current generator was drawn up. The parameters of the circuit elements (including the required number of capacitors and their charging voltage) are determined, which are necessary for getting a discharge current of a given standardized waveform and amplitude. The parameters of the discharge path are determined for surge arresters of three different voltage classes. It was found that the relative error when determining the residual voltage between the terminals of the surge arrester model does not exceed 3 %.
 The work contributes to the further development of circuit simulation of surge arresters and the expansion of the scope of surge arrester dynamic models. As a result of the research performed, the possibility of using surge arrester frequency-dependent models for determining the discharge current waveform in impulse current generators is shown. The research performed is relevant due to the fact that surge arresters have become a main tool for protecting the insulation of electrical network equipment against external and internal overvoltages
Highlights
Surge arresters are designed to protect the insulation of electrical equipment against switching and lightning overvoltages
Refinement of the active resistance R3 and inductance L3 is performed at the stage and is the subject of another scientific research. It is shown for the first time that dynamic models of surge arresters can be directly used to determine the main parameters of an impulse current generator designed for full-scale testing of surge arresters
It is shown that with a help of circuit simulation, it is possible to select the parameters of the circuit elements necessary to obtain a discharge current with a given amplitude and waveform, which must pass through the surge arrester according to the test conditions
Summary
Surge arresters are designed to protect the insulation of electrical equipment against switching and lightning overvoltages. One of the main characteristics of a surge arrester is the residual voltage, that is, the voltage that appears between its terminals during the passage of a discharge current through it It is the peak value of the residual voltage during the passage of switching current impulse and lightning current impulse that mainly characterizes the protective properties of the surge arrester. If the parameters of the test object are linear, ready-made relations [2], which have been used for several decades, can be used to calculate the impulse current generator parameters In this case, the test object is a surge arrester, which varistors have a highly non-linear current-voltage characteristic. In addition to the above, it should be noted that the surge arrester is characterized not just by a nonlinear, but by a dynamic nonlinear current-voltage
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