Design and development of a cable impedance spectrum testing system based on dual-path IV

In order to meet the demand of impedance spectrum measurement for cable fault detection, based on Line Resonance Analysis (LIRA), combined with the cable distribution parameter model, we improve the circuit structure of the traditional “half-bridge method” of impedance measurement by applying two symmetrical auto-balanced bridges to realize the impedance measurement in a wide frequency range from 100KHz to 10MHz. The system adopts the STM32FDNS to measure the impedance in a wide frequency range from 100KHz to 10MHz. The system adopts the STM32F103RCT6 as the core of the main control system, the excitation system, the core measurement system applying two symmetrical auto-balanced bridges, and the human-machine interface. The experimental results show that the design innovation of two-way symmetric automatic balanced bridge compensates for the amplitude and phase of the signal to be measured, realizes the stable output of the ratio of the signal to be measured, with the ratio error not exceeding 0.2%, and the resonance period of the cable impedance spectrum and the impedance amplitude obtained are in line with the accuracy requirements of the LIRA for locating cable faults, and ultimately realizes that the cable fault distance localization error The error of cable fault distance localization is not more than 0.37%.