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Offshore high voltage DC (HVDC) wind farms offer a promising solution to growing energy demands in the future. Condition monitoring of substation assets is essential for reliable and resilient operation of electrical networks. Existing condition monitoring techniques for onshore substation and electrical network assets include regular and scheduled on-site visits by trained personnel to substation sites. However, such routine inspection is not a cost-effective solution for offshore sites. In cases where the accessibility to network assets becomes difficult, robotic and autonomous condition monitoring provides a solution. Such a robotic/autonomous solution would need to interact with the surrounding substation environment, without increasing the risk of electrical breakdown and flashovers between different energized components. In Part A of this paper, the effect of high electrostatic fields on an inspection unmanned aerial vehicle (UAV) is analyzed, with respect to: 1) AC corona emissions interference on the UAV, and 2) Air breakdown clearance characteristics. Both simulations and experiment results presented in the paper show the impact of corona emissions interference to both UAV autopilot and actuation sections, which requires a shielding mitigation solution. Also, experiment results show the limited effect of introducing a shielding solution on increasing the flashover risk between valve hall towers.

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This paper reports on a method combining the use of finite element simulations and external measurements to provide preliminary condition diagnosis of oil-filled cable sealing ends (CSEs) without requiring downtime. Good agreement has been obtained between the predictions from the electric field and thermal simulations and the measurements on a 132 kV oil-filled CSE. The electrostatic computation combined with electric field measurements can provide information regarding the electric field distribution inside the CSE and help in identifying potential issues with the CSE design, the materials or the cable termination process. The thermal computation combined with thermal imaging can reveal potential problems, such as high resistance connection to the busbar, and provide information regarding the cooling efficiency of the liquid dielectric. The method presented can provide the starting point for prioritizing maintenance operations on CSEs.

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