Abb Research Ltd.

Walter Rueegg

Bernhard Deck

Michael Stanimirov

Lutz Niemeyer

Klaus-Dieter Weltmann

Ralf-Dieter Pietsch

The method described here makes it possible to determine the impedance of a line ( ) by measuring the voltage (u) applied across the line and the time derivative of the current (i) flowing through the line. The measured values of the differentiated current are not integrated in this case, but rather are substituted directly, together with the measured voltage values, into an equation system from which the values of the inductance (L) and the resistance (R) of the line ( ) can be estimated. In this way, integration of the values of the differentiated current is obviated.

Method for measuring the resistance and the inductance of a line

Current and voltage values (uk, ik) are measured for protection of an electrical power line ( ). An adaptive estimator is used to analyze all the values within a measurement window, and to convert them to impedance values (Z). The line ( ) is switched off if the impedance values (Z) assume unacceptable values. In order to shorten the reaction time, a warning signal (W) is produced if powerful radio-frequency signals are detected on the line ( ). When the warning signal (W) occurs, the respective measurement window is located such that its start matches the time of the warning signal (W), and/or the respective measurement window is shortened.

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Endingen, Switzerland

Walter Rueegg