Wideband chirp voltage injection method for cables under the new power system

In-service power distribution cables are prone to frequent operational failures resulting from insulation aging, which threatens the safe and stable operation of urban and rural power distribution networks. Conventional online insulation monitoring technologies for distribution cables exhibit prominent limitations in engineering applications. Owing to the internal layered structure of power cables, complex on-site electromagnetic interference, diverse laying modes, and harsh environmental conditions of distribution stations, most traditional monitoring methods suffer from poor signal anti-interference ability, low measurement accuracy, and considerable field wiring challenges, thereby limiting their widespread application and stable operation.

To address these limitations, this study develops a novel online insulation-condition monitoring method for distribution cables based on wideband chirp voltage injection. At the core algorithm level, capacitance reference-signal measurements are used to calibrate the acquired data in real time and reduce measurement errors induced by the distributed capacitance of long-distance cables and the parasitic parameters of coupling loops, thereby jointly enhancing monitoring stability, sensitivity, and measurement precision. In terms of engineering access implementation, this study comprehensively considers the internal layout, busbar arrangement, and mechanical structure of the centrally installed switchgear and designs a new neutral-point coupling universal access scheme in strict accordance with power construction safety specifications, live working requirements, and electrical safety distance standards. This access mode features convenient installation, reliable electrical isolation, and strong universality for different types of cabinet bodies and cable loops. To verify the effectiveness and robustness of the proposed monitoring principle, signal injection strategy, and access scheme, a comprehensive verification system consisting of a simulation analysis platform and a field pilot test platform is constructed.

Comparative tests and data analysis show that the proposed method accurately realizes continuous online monitoring of the insulation deterioration state of distribution cables and provides quantitative judgment on the insulation aging degree. Moreover, the method successfully overcomes two long-standing technical limitations of similar injection-type monitoring devices: the lack of stable long-distance transmission of weak injected wideband signals and the lack of high-fidelity sensing coupling between excitation signals and cable insulation loops. The proposed method features outstanding anti-interference performance, reliable monitoring, and feasible on-site construction, highlighting its strong technical maturity, broad engineering potential, and considerable application value in the evaluation of the full-cycle condition of distribution cables.