This paper presents a review of the recent trends and the current state of the art in the application of fiber optic fiber Bragg gratings (FBG) sensing technology to condition the monitoring (CM) and testing of practical electric machinery and the associated power equipment. FBG technology has received considerable interest in this field in recent years, with research demonstrating that the flexible, multi-physical, and electromagnetic interference (EMI) immune in situ sensing of a multitude of physical measurands of CM interest is possible and cannot be obtained through conventional sensing means. The unique FBG sensing ability has the potential to unlock many of the electric machine CM and design validation restrictions imposed by the limitations of conventional sensing techniques but needs further research to attain wider adoption. This paper first presents the fundamental principles of FBG sensing. This is followed by a description of recent FBG sensing techniques proposed for electric machinery and associated power equipment and a discussion of their individual benefits and limitations. Finally, an outlook for the further application of this technique is presented. The underlying intention is for the review to provide an up-to-date overview of the state of the art in this area and inform future developments in FBG sensing in electric machinery.

Latest wind turbine lightning protection systems have been refined to the point where lightning damage is now relatively rare. This is increasingly important as wind turbines move offshore where access for maintenance is more difficult than for most land-based wind farms. Manufacturers have been trying to make sure that the lightning protection systems they install comply with the highest protection levels stipulated in the relevant IEC standards. In this study, data from the Nysted Offshore Wind farm in Denmark and that from a large number of other wind turbines worldwide is reviewed to show the range of lightning currents that have been measured on wind turbines currently in operation. These current values are compared with the required protection levels within the standards.

The aim of this article is to present a review of the development and application of superhydrophobic insulation for outdoor high-voltage applications. The methods of preparing insulation exhibiting superhydrophobic properties to mitigate the pollution problem under high voltages in the outdoors are explored. In addition, the existing evaluation techniques at the material development stage are reviewed and potential new modifications are discussed. The self-cleaning and anti-icing properties, the electrical performance, and prospects of superhydrophobic insulators are also addressed. Although superhydrophobic insulators may show promising behavior in small-scale laboratory conditions that do not use electrical stress, the effect of surface micro–nano structure responsible for the superhydrophobicity on the performance under the actual outdoor and weathering conditions under voltage remains to be fully understood and verified. Therefore, there is a need to verify the feasibility of superhydrophobic insulators for outdoor high-voltage applications with a solid evaluation protocol, while using material screening methods in the laboratory, and with reference to field experience.

Insulating cross-arms (ICAs) allow compaction or upgrading of transmission lines. The process of designing and verifying the performance of electric-field grading devices is reported for rigid cross-arms on a 132 kV lattice tower. For the grounded end, traditional grading devices resembling rings which follow the general shape of the insulators were designed. For the high-voltage end, an iterative process yielded a novel grading device which is a unibody piece of cast aluminium that manages the field on all four ICA members. Finite-element analysis simulations show that the electric-field magnitude at the triple junctions of the insulating members meet the design criteria of 3.5 kV/cm. Also, the field magnitude on the metallic end-fittings and electric-field grading devices is maintained below 18 kV/cm. The corona extinction test was performed on ICA assemblies showing that the grading devices can effectively control the electric field at voltages up to 132 kV since the average corona extinction voltage was 173.7 kV, well above the required value. The complete ICA assemblies were installed on an existing line in Scotland in August 2013. This paper provides a set of recommendations for use of FEA in the design of complex insulation geometries.

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.

Wind turbine lightning protection systems have been developed to the point where lightning damage is relatively rare. However, with windfarms moving offshore, manufacturers are striving to continuously improve lightning protection systems while ensuring that they comply with relevant IEC standards. The case of offshore wind farms is particularly important due to the difficulties faced in accessing a wind turbine should this be required owing to lightning damage. The paper details work done to model upward propagating lightning strike attachment on a wind turbine. A 3D electrostatic model of a full scale wind turbine has been modelled using available finite element analysis software. This full scale model is subjected to high electric fields comparable to those created by a charged cloud. Results from these simulations are then compared with those found from analysis of real lightning strike data taken from wind turbines and windfarms across the world.