摘要：The object of research is an analytical expression for representing the switching current impulse of a surge arrester. Any current impulse (both lightning and switching) is characterized by such parameters as the virtual front time and the virtual time to half-value on the tail. According to the standard IEC 60099-4:2014, switching current impulse has a virtual time to half-value on the tail of roughly twice the virtual front time. This requirement is one of the most problematic places in this task. The existing approaches used to represent lightning current impulses are not suitable in this case, since these impulses have virtual time to half-value on the tail of two and a half times the virtual front time.This problem can be solved with a help of analytical piecewise continuous functions.It is shown how to describe switching current impulses of the surge arresters with a help of analytical piecewise continuous functions. In contrast to other expressions, the resulting expressions for the switching impulse have only one parameter (angular frequency). Instead of approximate calculation, the front time of the resulting impulse is calculated by an analytically exact formula. Hence, the tolerance of virtual front time is equal to zero. The time to half-value on the tail of the resulting impulses is determined with some error that can be reduced by some complication of the original expression.The proposed functions satisfy the requirements of the IEC60099-4:2014 standard regarding switching current impulses of surge arresters. These functions allow representing current impulses having virtual time to half-value on the tail of roughly twice the virtual front time (30/60 or 45/90 microseconds). In such cases, minimal tolerance of time to half-value on the tail is +3.78%. Additional study shows that one of proposed functions allows representing current impulses having virtual time to half-value on the tail of two and a half times the virtual front time (8/20 or 4/10 microseconds). Tolerance of time to half-value on the tail for such impulses is 0.55%. The obtained functions are intended for study of various models of metal-oxide surge arresters on personal computers.
关键词：surge arrester;residual voltage;switching current pulse;piecewise function
