The burgeoning demand for enhanced power-system safety means that there is increased attention on technologies for the detection and location of cable faults. The double-terminal fault location method, which senses a fault current using a current transformer (CT), is the most effective and widely applied method in industrial practice. However, CT sensors may suffer from magnetic saturation when exposed to a high fault current, resulting in significant location errors, and their sensitivity cannot be adjusted. To address this problem, this paper describes an improved method for the acquisition of fault signal and the identification of fault-wave arrival time in power cables. First, a novel noncontact sensor (NCS) is developed for the detection of electric fields, and its sensitivity-adjustment curves are obtained by theoretical calculation and simulation. Then, based on feedback variational mode decomposition (FVMD) and the Wigner-Ville distribution (WVD), an improved method (the FVMD + WVD method) for the identification of fault-wave arrival time is devised, and its efficacy and accuracy are verified by simulations in Power Systems Computer-Aided Design/Electromagnetic Transients including DC (PSCAD/EMTDC) software. Finally, the fault-wave arrival-time detection performance of the NCS is examined in a series of on-site DC and AC experiments based on damped AC technology. The results show that the NCS exhibits feasible and effective performance, and that its response can be appropriately tuned based on its sensitivity-adjustment curves. The FVMD + WVD method is more accurate than several other current methods, as its error is only 0.48%, and thus this method enables the practical location of cable faults. In sum, these findings demonstrate that the NCS and the FVMD + WVD method comprise an improved system for the detection and location of cable faults, which will enhance cable safety in power systems.

Damped AC (DAC) technique has proven to be one of the most acceptable techniques for on-site partial discharge (PD) detection. However, the expensive high-voltage switches, used in the DAC system, impede the further spread of the technique. This letter presents a low-cost DAC system for PD test of high-voltage cables. The DAC voltage is generated by the frequency-tuned series resonant technique and two cost-effective switches which have relatively low rated voltage. Since the system uses a capacitor bank, high input power is not necessary. This letter describes the design and implementation of the system. An experimental study and an on-site test validate the effectiveness of the proposed system.

Partial discharge (PD) diagnosis is a crucial technique for assessing the insulation condition of high-voltage (HV) cables. The double-sided travelling wave method is effective for online PD localization on HV cables. However, the PD localization accuracy is limited by three main factors: inaccurate time synchronization among sensors, imprecise pulse propagation velocity, and noise interference. To address these issues, a bidirectional pulse-injected time synchronization method is proposed to correct the timing bases of detectors and assess the pulse propagation velocity along cables independently of cable parameters. Furthermore, a denoising method combining the short-time Fourier transform (STFT) and variational mode decomposition (VMD) is designed to enhance the robustness of the system to high-intensity noise. Finally, an integrated PD detector with pulse injection and signal detection functions and switchable measurement ranges is designed to improve detection sensitivity. To validate the effectiveness of the proposed method, a portable system is developed, and experiments are conducted on both a 10 kV cable in the laboratory and a 110 kV cable in the field. The experimental results confirm that the proposed method enhances the accuracy of PD localization.

As an important part of asset maintenance strategy, power utilities carry out insulation testing of power cables to diagnose and assure their health condition. Among various testing methods, very low frequency cosine-rectangular voltage (VLF-CRV) testing is a relatively new approach that has been recently proposed because of its significant advantages of high efficiency, multi-functionality and easy transportability. This study shows the design, implementation and confirmation of the topology of a novel VLF-CRV generator based on voltage multiplier that avoids separately using HVDC sources and high voltage switches, thus accordingly strengthening its scalability. Note that the mathematical modes of the generator are presented for comprehensive analysis and optimization of the VLF-CRV generator. Simulation in MATLAB/Simulink is performed to validate the generator's feasibility and implementation of a laboratory prototype is also detailed. Moreover, experiments on a capacitor and a medium voltage power cable were performed to confirm the effectiveness of our implementation. 1

In this letter, a novel damped AC (DAC) generator is proposed and implemented, whose working principle is based on the seamless combination of the high voltage (HV) DC source and the HV solid switch by replacing the diodes in the voltage multiplier (VM) with controllable insulated gate bipolar translators (IGBTs). Both laboratory tests on a lumped capacitor and field tests on a 10kV MV cable were performed to prove the feasibility of the proposed techniques.

Partial discharge (PD) and dielectric dissipation factor (DDF) tests are important to ensure the safe and stable operation of high-voltage power cables. However, it is difficult for the existing test system to meet the requirements of both tests. Therefore, this paper presents a short-time AC high-voltage generator and testing system for cable’s PD and DDF measurement. Firstly, the schematics based on cascade H-bridge and series resonance are presented. Then some key technologies and design methods of key components are given, including the design of the inductor based on optimization principle and field-circuit coupling, the DDF measuring method which can ensure the safety of the test cable, and the optimization control algorithm based on state equation. The implementation then is given and an experiment is carried out to generate the target voltage. A variable DDF standard capacitor is used to verify the effectiveness in DDF measurement and a field test case is given where the effectiveness in measuring PD is verified. Compared to existing methods, the proposed approach provides greater load capacity, a more compact and lightweight design, and extended nominal voltage duration. Additionally, it enhances DDF precision, achieving a 1e-4 resolution for more accurate measurements.