Analytical representation of switching current impulses for study of metal-oxide surge arrester models

Abstract

trotsenko ye., Brzhezitsky V., Masluchenko I. IntroductionModeling of a metaloxide surge arresters is necessary for calculating lightning and switching surges using personal computers. At the present time, there are several similar dynamic (that is, frequencydependent) models of a metal oxide surge arrester [1,2]. As a rule, these models consist of two nonlinear resistances connected to each other by means of several linear elements: inductances, resistors and capacitance. Surge arresters have several main characteristics. Among others, these characteristics the residual voltage of an arrester, which is the peak value of voltage that appears between the terminals of an arrester during the passage of discharge current with given shape and amplitude. There are residual voltages of the arrester for nominal discharge current (lightning current impulse), switching current im pulse and for steep current impulse. The surge arrester model should reproduce in the virtual experiment on the computer exactly these abovementioned characteristics of a real arrester. To draw a conclusion about how well this or that model reproduces the behavior of a real arrester, it is necessary to compare the simulation results with the corresponding values that manufacturers give in the catalogs of their products. For computer simulation, a formula is needed to describe the dependence of the discharge cur rent on time. The analytical representation of the nominal discharge current (lightning current impulse) and steep current impulse does not present such difficulties as the representation of the switching current impulse. As a rule, manufacturers indicate residual voltages at several amplitudes of the lightning current impulse and at several amplitudes of the switching current pulse. In order to be able to test the model with as many control points as possible, it is necessary to consider problems related to the analytical representation of switching current impulses of arresters. the object of research and its technological auditThe object of research is an analytical expression for representing the switching current impulse of a surge ar rester. Any current impulse (both lightning and switching) is characterized by such parameters as the virtual front time T 1 and the virtual time to halfvalue on the tail T 2 . However, there are differences in the requirements for the accuracy of lightning and switching current impulse parameters of surge arresters.According to the standard IEC 600994:2014, the lightning current impulse is defined as follows. Lightning current impulse is 8/20 current impulse with measured values from 7 μs to 9 μs for the virtual front time and from 18 μs to 22 μs for the time to halfvalue on the tail. That is, the permissible error for both T 1 and T 2 , is ±10 %. Regarding the switching current impulse, the standard IEC 600994:2014 sets the following. Switching current impulse of an arrester has a virtual front time grea ter than 30 μs but less than 100 μs and a virtual time to halfvalue on the tail of roughly twice th...

Analysis and comparison of metal-oxide surge arrester models

“…In order to represent the current impulses with the 8/20 μs waveform, expression (4) was used in accordance with [15]. …”