There are some studies in the literature in order to make the interpretation of human tissues having different characteristics. Some of these studies focused on the evaluation of human face tissues. Vibration signals generated from vocal cords have been used in these studies about human face tissues. However, any study using the vibration signals recorded by applying the external vibration source having fixed frequency value is not available in the literature. In this study, it is aimed to investigate the frequency characteristics of the vibration signals recorded from the human face. These signals obtained from nine different regions on the faces of subjects are analysed using frequency characteristics. In the analysis stage, median and maximum frequency values are calculated and evaluated. So, the softness and hardness interpretation about these regions on the face can be made and the frequency ranges of these regions can be determined. As a result, it is observed that low-frequency signals are dominant in hard regions and high-frequency signals are dominant in soft regions.

The reliable technique for identification of winding insulation faults in a transformer is necessary for a testing engineer during impulse test. In this study, a statistical correlation technique is proposed to estimate the ‘best correlation’ between transient signals for passed (withstood the impulse voltage) or failed (not withstood) conditions of the insulations. In this study, normalised reduced impulse voltage is considered initially as a reference signal. The next successive impulse test sequences due to rated test voltage are correlated as a test signal with a reference signal using a proposed technique. It makes a ‘good correlation value along with its directions’ between the reference signal and test signal based on measured the applied impulse voltage waveshape and its winding response. The fundamentals of the correlation coefficient, curve fitting techniques, conditional variance, normalisation and time delay index are integrated effectively to predict the characteristics (degree/magnitude and direction) of correlation between the signals. 2.5-MVA 11/0.433 kV (distribution transformer), 0.3-MVA 34.5/0.415 kV (earthing transformer) and 250-MVA 500/275/33 kV (power transformer) are effectively utilised to validate proposed technique. The advantage of the proposed technique is validated with partial discharge detection in windings due to an impulse voltage application using an 11 kV single-layer winding.

The construction of the ubiquitous power internet of things (UPIoT) provides a new feasible solution for gas-insulated switchgear (GIS) online monitoring and fault diagnosis, but it also puts forward greater requirements for time and accuracy. How to find an effective real-time model that can be applied to the UPIoT mobile terminals has become an urgent problem needing to be solved. To this end, this study proposes a lightweight convolutional neural network (LCNN) for GIS partial discharge (PD) pattern recognition using three lightweight convolutional blocks, and introduces the lowest recognition accuracy of single-class faults as the primary indicator for selecting the optimal model under the UPIoT. First, three lightweight convolutional blocks are introduced for constructing an LCNN. Then, the optimal model constructed by the lightweight blocks is sought. Next, criteria for determining the best model are introduced, and the best model under the UPIoT is selected. This study provides a reference standard for the construction of GIS PD pattern recognition under the UPIoT. Meanwhile, through the balance of evaluation indicators, this study verifies that the minimum recognition accuracy of the MnasNet model is 98.8%, which is obviously better than other methods and lays a solid foundation for GIS PD pattern recognition.

This study deals with the electrical breakdown characteristics of the sphere-plane electrode system with the dielectric barrier of bulk moulding compound (BMC) material under the positive lightning impulse voltage. The sphere electrode has a spherical shape of 50 mm in diameter and suspended with a metal rod of 10 mm in diameter, while the plane electrode has a circular with a diameter of 350 mm. The dielectric barrier has a square plate shape of BMC material, and the dimension is changed from 80 × 80 to 240 × 240 mm². Experimental results show that electrical breakdown paths could be identified into three categories, depending on the dielectric barrier position and the dimension. The larger and farther away from the sphere electrode the dimension of the dielectric barrier is, the occurrence probability of electrical breakdown through the penetration of dielectric barrier becomes. It was confirmed that the breakdown voltage considerably depends on the dimension of the dielectric barrier and the dielectric barrier position.

This study presents a novel fast Fourier transform (FFT)-based non-contact vibrational harmonics measurement system using a position sensitive detector (PSD) along with calibration using a piezoelectric accelerometer. Frequency-domain vibrational analysis is required as the changes in machine dynamics are directly related to its failures and could provide more insight into the vibration signal. In this regard, FFT is used for spectral analysis to detect the harmonics in the vibration signal. The novelty of the applied technique for detecting vibrational harmonics lies in its innate contactless nature where the vibration detection sensor i.e. PSD is placed at a particular distance from the vibrating target. Additionally, the parasitic and external vibrations, which might pose unforeseen errors in the detected vibration data, have been nullified by employing a self-vibration technique using an ADXL-345 three-axis accelerometer. The results obtained through PSD have been calibrated via a standard Brüel & Kjaer (B & K) vibration measurement system which uses a piezoelectric accelerometer (B & K accelerometer). The proposed measurement technique is equipped with NI compact RIO-9074 that features a real-time processor and an FPGA. The system was observed to effectively measure the frequency range 5–600 Hz with a maximum relative error of 2% in FFT amplitudes.

Thrust testing units with a piezoelectric dynamometer have unique traits such as excessive stiffness, tremendous measurement accuracy, dynamic performance and no hysteresis. These are widely used in the applications requiring force/thrust measurements in the aerospace industry and high-end tool condition monitoring. The performance of these units is necessary to be evaluated. In this study, an improved layout of six-degree of freedom force/thrust measurement stand is proposed and analysed theoretically and experimentally. The measurement stand is a structural component to measure six components of force, such as axial force/thrust (F_X , F_Y , and F_Z ) and other components (M_X , M_Y , and M_Z ). Test stand consists of seven piezoelectric sensors in two sections. The front part consists of four piezoelectric force sensors, while the rear part consists of three sensors. The rear section is hexagonal, with three sensors mounted at 120°. The measurement stand can measure the principal force/thrust up to 50,000 N. A mathematical model is derived for every sensor against forces in all directions. To calibrate the stand, a calibration platform is designed and fabricated. The calibration platform can generate a range of forces/moments. Calibration experiments verifies that the measurement stand is fairly functional to measure variety of forces/moments with high repeatability.

Due to the differences in typical pollution sources, the soluble salt composition deposited on the naturally contaminated insulators varies with the region. As different soluble salts have different effects on the pollution flashover voltage of insulators, it is necessary to investigate the spatial and temporal distribution of the soluble salt composition deposited on the insulator surface to make the external insulation design more scientifically and reasonably. In this study, an artificial contamination test platform was built to collect the contamination naturally deposited on the specimens. The test results showed that the contamination composition deposited on the specimen was similar to that in the atmosphere, and the inclination angle of the specimen and the duration of pollution deposition had little influence on the contamination composition. After examining the industrial post insulators from actual substations, it was found that the contamination composition was almost the same for different insulator surface materials, insulator shed types, and voltage polarities. It was also found that the deposited contamination was mostly influenced by pollution sources. The results can provide a reference for the studies of pollution distribution of natural insulators.

An efficient analytical method based on the Baum–Liu–Tesche (BLT) equation has been developed for predicting the shielding effectiveness (SE) of an apertured enclosure excited by an external plane wave. First, the equivalent circuit and the signal flow graph are constructed, which helps understand the energy transmission of the enclosure. Then, the SE is obtained by using the generalised BLT equation, and the proposed analytical method is employed to analyse the effect of various parameters on the SE. Finally, the analytical method is extended to handle the enclosure with an aperture array, an enclosure with apertures at the opposing walls and two cascaded enclosures. The analytical method has been successfully verified by the CST over a wide frequency band of 0–3.0 GHz, which consumes less time than conventional numerical methods. Besides, whatever the condition of the enclosure or the aperture is, the analytical method can predict the SE and higher-order modes at higher frequencies accurately.

The communication circuit network is widely employed for signal transmission in high-voltage pulse driver system, for commanding, controlling, measurement & communication. The electromagnetic compatibility of the communication circuit network mainly decides the stability and reliability of the high-voltage pulse driver system. Aiming at the electromagnetic interference (EMI) problems of the RS422 communication circuit in the Tesla pulse driver, the generated disturbance sources and characteristics from the Tesla pulse driver itself are analysed in five divided work stages, and two typical simplified EMI coupling modes for the communication circuit are also presented in this Letter. In the RS422 communication cable circuits between the subsystems of the pulse driver, the time-domain resonant characteristics of the communication signal and the conducting disturbances are analysed. The error and failure modes of the RS422 communication data caused by the full time-domain conducting interference are also revealed. Evaluation and calculation method for the time-domain resonant probability and the interference probability of the RS422 communication signals is also put forward. The communication interference probability is also calculated under different repetition work modes of the Tesla pulse driver. In view of the time-domain resonance phenomenon, some effective ways for time-domain resonance elimination and interference compression are put forward.

This study proposes a three-dimensional (3D) quasi-static modelling of the electric field produced by high voltage (HV) overhead power lines using charge simulation method combined with intelligent optimisation algorithms, such as particle swarm optimisation, genetic algorithm and grey Wolf optimiser (GWO), to find the optimal values of parameters for an accurate calculation. Results show that the GWO works better than other algorithms. Several parameters affecting the electric field have been studied; it is observed that taking into account the effect of the exact catenary curve of the power line conductors is much more interesting particularly at the mid-span level where the electric field becomes very significant. According to these values, the limits set by the International Commission on Non-Ionising Radiation Protection guidelines for electric field strength are met for occupational and public exposure. The simulation results are compared with those obtained by the 3D Integration method, a fairly good agreement is found. To confirm the performance and effectiveness of the proposed method, the results obtained are also verified with measurement values available in the literature, a good similarity is achieved.

This study presents a grid-searching method in polar coordinate system (GSMIPCS) for the partial discharge (PD) location, in which the grids were divided into sectors according to radial distance r, azimuthal angle θ and polar angle φ. After theoretically proving that the positioning angle error, based on time difference of arriving algorithm, is relatively small, this study gives the process of PD positioning in two-dimensional and three-dimensional polar coordinates. Thereafter, this study discusses the optimal setting of grid parameters. The simulation results show that the success rate of angle positioning (SROAP), i.e. a percentage of positioning number with positioning angle error <2° in the total positioning number, for θ angle using two-dimensional (2D) GMSIPCS is 95.87%. For 3D GMSIPCS, the SROAP for θ and φ are 86.18 and 92%, respectively; and the computational cost is lower to 216. Finallly, on-site experiments in the substation verify the effectiveness of the proposed method.

An efficient analytical method based on the Cohn model and mirror procedure is proposed for the prediction of the shielding effectiveness (SE) of a rectangular enclosure with electrically large apertures. Firstly, the coupled electromagnetic fields are represented by the equivalent dipole moments located at the centre of the aperture according to the Cohn model, where the dipole moments can be calculated based on the mirror procedure. Then, the vector potentials can be obtained through the relation between the dipole moments and the current distribution. Finally, the total electric fields are obtained by using the vector potentials, thus the SE and most of the resonant modes can be predicted accurately and fast. The SE results which have been verified by the CST over a wide frequency band of 0.01–3.0 GHz show that the proposed method is effective in handling the enclosure with electrically large apertures, including the multiple apertures arranged in different ways and hybrid apertures in different shapes and dimensions.

A new method for the fault location in a short cable line is proposed in this study. Based on the transmission line theory and circuit theorems, an analytical expression for estimating the fault location in the cable line is derived. According to the problem of incorrect estimation in the high-frequency band, the corresponding essential reason is comprehensively explained. By solving this problem, the fault location can be obtained accurately by the proposed method. To validate the proposed method, some experiments with a 50 Ω coaxial cable are implemented and the accuracy of the proposed method is tested. Meanwhile, it has been validated in these experiments that the proposed method is independent of the fault impedance and terminal impedances.

In this study, the authors present results of a call testing campaign using voice over long term evolution (VoLTE) technology on the radio access network of the operator Telecom Italia mobile. The quality of the voice call is expressed by means of the mean opinion score (MOS). The electromagnetic propagation environment has been reproduced within a reverberation chamber, and its effect on MOS has been evaluated by varying the signal strength, i.e. the reference signal received power and the signal-to-interference noise ratio. The aim is to find a correlation between the radio propagation environment and the perceived quality of the speech. Regardless of the networks technology, voice quality could be impacted by several factors: traffic load of LTE evolved Node B, quality of service, radio pathloss, mutual radio interference, multipath and so on. Interference and multipath are added to the useful signal in order to deteriorate the MOS, until the VoLTE calls dropped. Target of such work is to properly set the thresholds that trigger a handover of single radio voice call continuity to other radio access technologies (UMTS or GSM). Tests take also into account the adaptive multi-rate CoDec selected by the network.

This work presents the mutual influence of nearby grounding structures on each other in terms of safety parameters. To epitomise mutual influence, primarily a mathematical model of the double circuit transmission line, cling to the tower, close by a substation is considered. The model estimates the ground fault current venting into the encompassing soil, in case of single-phase to ground fault at the tower, when mutual resistive effects of both groundings are taken into account and when they are ignored. Neglecting these effects leads to a false estimation of safety parameters such as ground-fault current and touch voltages, which are frequently used in grounding design. It may lead to unnecessary expenditures on the safety design of the grounding system. For verification purposes, the practical application of the model is exhibited. Also, an interactive model between substation grounding (grid model) and nearby tower grounding (rod model) is examined in terms of safety parameters. To further validate, an experimental set up is built for two nearby groundings. Experimental results obtained through it are compared with the results of the finite-element method and analytical method and are found to be favourable. Touch, step, and ground potential distribution profiles with and without considering nearby grounding are also presented.

New solutions to a recently proposed benchmark TEAM problem for Pareto optimisation are presented. In the benchmark, an air-cored solenoid of small size, which can be used, for example, for magnetic fluid hyperthermia, is considered. Two shape optimisations of the solenoid are proposed in the benchmark: synthesising a uniform magnetic field in a control region, considering also a sensitivity function (Problem 1) or synthesising a uniform magnetic field, simultaneously minimising the power losses (Problem 2). The benchmark is solved by means of three different nature-inspired algorithms and a genetic one, namely micro biogeography-inspired algorithm, wind-driven optimisation, and the cuckoo search, taking the genetic algorithm NSGA-II as a reference, because all these methods have proven to be effective in solving multi-objective optimisation problems.

In this study, a multi-channel I–V curve tracer with the capability of measuring multiple photovoltaic (PV) modules has been proposed. An adaptive-sampling-rate method has been developed to enhance the I–V tracer's performance in terms of acquisition speed and data resolution in which enables the tracer to measure the I–V curve for a wider range of current and voltage with higher measurement points. This is important to provide rapid comparison and identification of faults that may have occurred in one or more PV modules. A low-cost prototype was built using an Arduino-based microcontroller, and the experimental tests were performed with 30 PV modules. The simulation and experimental results verified the performance and functionality of the proposed I–V curve tracer.

Carrying out the insulation condition measurement and analysis is important for the safe operation of the submarine cable. In this study, the high-voltage frequency dielectric response is used to identify the ageing state of the AC 500 kV cross-linked polyethylene (XLPE) submarine cable. The complex capacitance and tanδ in the low-frequency area for the new, thermal ageing, electro-thermal ageing cable all increase with the testing voltage increased from 200 to 2000 V. It is founded that the dielectric response at high voltage is more likely to detect the ageing differences. Based on the carbonyl index and the dielectric loss of the XLPE specimens at different position of the insulation layer, the non-uniform ageing phenomenon of the cable insulation is presented for the thermal ageing and electro-thermal ageing cable. The loss quantity parameter and its changing behaviour with testing voltage based on the frequency dielectric response could be used to identify the ageing state. The comparison of the modified Cole–Cole model parameter under 200 and 2000 V also indicates that the higher voltage dielectric response is helpful to identify the ageing differences.