Method and device for determining the division of a total insulation resistance and the division of a total system leakage capacitance in an ungrounded power supply system

Abstract

A method and device for determining a division of a total insulation resistance and of a total system leakage capacitance in an ungrounded power supply system. The basic idea is to determine how the total insulation resistance is divided into partial insulation resistances and how the total system leakage capacitance is divided into partial system leakage capacitances between the active conductors of the ungrounded power supply system from displacement voltages measured between each of the active conductors of the ungrounded power supply system based on values determined in advance for the total insulation resistance and for the total system leakage capacitance of the ungrounded power supply system. By evaluating the displacement voltages in terms of their changes in amplitude, their frequency and their phasing, conclusions can be drawn as to the division of the total insulation resistance and of the total system leakage capacitance between the individual active conductors.

1 . A method for determining the division of a total system leakage capacitance (C e ) in an ungrounded power supply system ( 2 ,  12 ) comprising active conductors (L + , L − , L x ) between which a conductor-conductor voltage (U dc , U ac , U acxy ) occurs, the method comprising the steps of:
 determining the total system leakage capacitance (C e ) of the ungrounded power supply system ( 2 ,  12 ), characterized by   measuring displacement voltages (U L+_E , U L−_E , U Lx_E ) between each of the active conductors (L + , L − , L x ) and ground (E),   determining a capacitance division factor (r C ), which describes the division of the total system leakage capacitance (C e ) into partial system leakage capacitances (C e+ , C e− , C ex ) related to the active conductors (L + , L − , L x ), as a function of at least one of the parameters amplitude, frequency, phase of the displacement voltages (U L+_E , U L−_E , U Lx_E ) measured.   
     
     
         2 . The method according to  claim 1 , characterized in that in an ungrounded DC power supply system ( 2 ), the capacitance division factor (r C ) is determined from the duration of a transient effect of the respective displacement voltage (U L+_E , U L−_E , U Lx_E ) caused by the change in amplitude of the conductor-conductor voltage (U dc ). 
     
     
         3 . The method according to  claim 1 , characterized in that in an ungrounded single-phase or multi-phase AC power supply system ( 12 ), the capacitance division factor (r C ) is determined from the relation of the amplitudes of the displacement voltages (U Lx_E ), taking into account the frequency and the phasing of the displacement voltages (U Lx_E ).