Abstract: A method and apparatus for measuring impedance of grounding system wherein a transient electric current is injected at the ground system under test while measuring the a transient ground potential difference, as well as the injected electric current. The ground potential difference is measured with respect to several points on the earth's surface at small distances from the test system. These measurements are processed by computer software which filters noise, corrects voltage and current transducer errors, and estimates the test system ground potential rise with respect to remote earth. Correction algorithms are used to remove irregularities in the frequency response of the voltage and current transducers and analog filters. The filtered and corrected measurements are used to estimate the ground impedance as a function of frequency. For this purpose, a parameter estimation procedure is used which takes into consideration the geometric arrangement of the voltage and current probes.

Abstract: Disclosed is an apparatus and method for continuously detecting skips, protrusions, protuberances and other defects in cable conductor shield, comprising a high voltage electrode, a capacitance bridge filter circuit and a corona discharge detector. A noncontacting coaxial electrode is employed to create an electric field between the cable conductor and the electrode. In the presence of this field, defects in the shield produce corona discharges. A detection circuit employing a capacitance bridge is employed to continuously detect corona discharges and produce signals used for subsequently locating the positions of the defects on the finished cable.