Background. To identify a fault section of a 110–500 kV mixed power transmission line, several methods are used. One of them is based on the application of positive‑sequence impedance measuring units. This method doesn’t fully allow determining the type of fault, as it has a dead zone for certain faults in the vicinity of the transition point from the overhead section to the cable section. Other methods based on the use of impedance measuring units can only be effective under specific ratios of the lengths of the cable and overhead sections. Thus, the task to improve the effectiveness of identifying the fault section of a mixed power transmission line using impedance measuring units is highly relevant.
Materials and methods. The study has been conducted using electrical circuit analysis methods and the method of symmetrical components. The implementation of a zero-sequence impedance measuring unit has been carried out in the MathCAD computer-aided design system. The research results have been processed using the MATLAB software package.
Results. A method to identify the fault section of a 110–500 kV mixed power transmission line is proposed, using zero-sequence impedance measuring units. This method demonstrates improved effectiveness compared to conventional positive-sequence impedance measuring units. A study has been conducted to investigate the influence of two factors on the effectiveness of the proposed method to identify the fault section: the mutual angle between the electromotive forces of the systems on either side of the mixed power transmission line of a real-world configuration, the arc resistance at the fault location.
Conclusions. The obtained results make it possible to improve the effectiveness of using impedance measuring units to identify the fault cable section of 110–500 kV mixed power transmission lines, followed by issuing a prohibition signal to block autoreclosing.