The state detection of power cables is very important to ensure the reliability of the power supply. Traditional sensors are mostly based on electric field detection. The operation is complex, and its efficiency needs to be improved. This paper optimizes the design and development of the magnetic field detection sensor for AC power cables. First, through the establishment of the magnetic field sensor model, it is determined that permalloy is the material of the magnetic core, the optimal aspect ratio of the magnetic core is 20, and the ratio of coil length to core length is 0.3. Second, the coil-simulation model is established, and it is determined that the optimal number of turns of the coil is 11,000 turns, the diameter of the enameled copper wire is 0.08 mm, and the equivalent magnetic field noise of the sensor is 0.06 pT. Finally, the amplifying circuit based on negative magnetic flux feedback is designed, the sensor is assembled, and the experimental circuit is built for the sensitivity test. The results show that the sensitivity of the magnetic field sensor is 327.6 mV/μT. The sensor designed in this paper has the advantages of small size, high sensitivity, ease of carry, and high reliability.

In order to improve the operation safety and stability of power cables, it is necessary to conduct targeted research on different grounding modes. Firstly, the appropriate cable parameters are selected according to the specific use, and the model is established in ATP-EMTP according to the selected cable parameters. Then, the availability of three grounding modes models of grounding at one end, grounding at both ends and cross-connection grounding (cable core grounding, shielding layer grounding and armor layer grounding) are compared and verified by simulation. Finally, by setting the shielding layers of different thicknesses as a comparison, the impedance and current characteristics of the cables under three different grounding methods are analyzed. The results show that the impedance values of the three grounding methods are basically the same. However, according to the current characteristics, when the shielding layer and the armored layer are cross-connected and grounded, the current of them is much smaller than that which is grounded by other grounding methods. Therefore, under the comprehensive consideration of economic benefits, this grounding is the best choice. This study provides guidance for the grounding mode of cable early laying, and provides reference for other cable related research.

With the rapid development of wind power generation, submarine cables have become a critical transmission channel for delivering offshore wind energy to onshore power stations. Because of the difficulty of submarine-cable maintenance, particular attention should be paid to their overvoltage characteristics during operation. Taking a ±200 kV DC submarine-cable project as the research background, this paper establishes a PSCAD/EMTDC model of a two-terminal MMC-HVDC submarine-cable system and compares the conductor-to-ground overvoltages caused by faults at different electrical locations. Among the investigated AC-side cases, single-line-to-ground faults on the valve sides of the connecting transformer and bridge-arm reactor produce relatively high cable overvoltages, with the bridge-arm-reactor valve-side fault reaching a maximum of 2.48 p.u. (496.48 kV). Among all investigated cases, the grounding fault on the valve side of the DC reactor produces the highest overvoltage, reaching 2.93 p.u. (586.18 kV) at approximately 30 km along the cable. After the initial transient associated with the DC-side grounding faults, the healthy-pole conductor-to-ground voltage remains at approximately 2.0 p.u. The results identify the relatively severe fault locations and cable sections requiring particular monitoring attention and provide a case-specific reference for DC submarine-cable monitoring and subsequent project-specific insulation-coordination studies.

With the large-scale development of deep-sea offshore wind power, the insulation safety of high-voltage submarine cable outer sheaths faces severe challenges, yet the propagation characteristics and coupling mechanisms of cable-core overvoltages to the metal sheath remain unclear. To address this, a physical experimental platform was established for lightning impulse testing based on a 66 kV submarine cable, and the transient potential response characteristics of the metal sheath under various operating conditions were systematically investigated. The results indicate that under fully suspended conditions, the sheath voltage is primarily determined by the voltage division caused by the radial coaxial distributed capacitance. When a 30.6 kV lightning impulse voltage is applied, the overall potential of the sheath approaches that of the cable core; under conditions where the sheath is grounded at the end, the capacitively coupled charge is rapidly discharged, and the transient potential is then dominated by inductive coupling, with its variation strictly corresponding to the rate of change in the cable-core’s transient current; under conditions where the sheath is fully suspended and the cable core is grounded, the potential of the metal sheath exhibits a dynamic superposition of the radial capacitive common-mode voltage and the axial inductive differential-mode potential difference. These findings demonstrate that metallic-sheath grounding conditions significantly influence the relative contributions of capacitive and inductive coupling to transient sheath overvoltages under lightning impulse excitation. The experimental results provide a physical basis for further investigation of sheath grounding arrangements and overvoltage protection strategies.