Method, circuit and apparatus for the elimination of the d.c. voltage components of a capacitive a.c. voltage divider

摘要

In a method for the elimination of the d.c. voltage components of a capacitive a.c. voltage divider whose a.c. measuring voltage which may include a d.c. voltage component, is fed to a measurement transformer, the task is to be solved to remove as quickly as possible the d.c. voltage component of the a.c. measuring voltage also to the greatest extent possible without falsification of the reproduction of the middle or high voltage to be measured. This is achieved in that the a.c. measuring voltage (UM) is fed to a measuring amplifier (14) by way of two parallel lines (L1, L2) via a d.c. voltage blocking element (6). The a.c. measuring voltage (UM) is thereby fed directly by way of one line (L1) and the d.c. voltage component (UG) of the a.c. measuring voltage (UM) is determined in the other line (L2) in that the a.c. measuring voltage (UM) is subdivided into such small time sections (t) that an equal number of time sections is coordinated per cycle (T) or half cycle (T/2) and the a.c. measuring voltage is continuously integrated over a period (T) at the frequency (Tf) of the time sections (t). The thus-determined respective d.c. voltage value (UG) is fed to the measuring amplifier (14) in phase opposition to the original value and by way of the latter to the measurement transformer (16) (FIG. 1).