In this study, two formulations for the robust optimisation of the size of the permanent magnet in a synchronous machine are discussed. The optimisation is constrained by a partial differential equation to describe the electromagnetic behaviour of the machine. The need for a robust optimisation procedure originates from the fact that optimisation parameters have deviations. The first approach, i.e. worst-case optimisation, makes use of local sensitivities. The second approach takes into account expectation values and standard deviations. The latter are associated with global sensitivities. The geometry parametrisation is elegantly handled thanks to the introduction of an affine decomposition. Since the stochastic quantities are determined by tools from uncertainty quantification (UQ) and thus require a lot of finite element evaluations, model order reduction is used in order to increase the efficiency of the procedure. It is shown that both approaches are equivalent if a linearisation is carried out. This finding is supported by the application on an electric machine. The optimisation algorithms used are sequential quadratic programming, particle swarm optimisation and genetic algorithm. While both formulations reduce the size of the magnets, the UQ-based optimisation approach is less pessimistic with respect to deviations and yields smaller magnets.

The windings of the power transformers are prone to deformation or displacement as a result of huge electromagnetic forces. Regular monitoring of transformers for detecting minor winding movements is crucial for preventing them from developing into major faults and eventually, causing an outage. In this study, a novel procedure is proposed to determine the location and severity of the disk space variation, a frequently occurring mechanical damage in transformers, by developing a two-level method. At the first level, an accurate model of the winding is determined from sweep frequency response analysis measured data corresponding to the healthy status. Analysis and interpretation of the obtained results by the proposed fault detector algorithm lead to locating the position and severity of the fault, in the next level. The process of determining the winding model from the frequency response analysis data is achieved by a multistage method utilising an enhanced version of magnetic optimisation algorithm, which comprises of utilising Fourier series coefficients and phase functions, and fast calculation of coupled network matrices. Experimental results of two 64 kV transformer windings verify the effectiveness of the proposed method in detecting the winding faults.

The lightning progression model has been implemented in this article to study the performance of the lightning protection system to the launch site. For this purpose, a real-size exemplary protective system has been used for simulation and a laboratory-scale exemplary system has been applied for both simulation and experimental testing applications. Surveys and simulations are both conducted in a three-dimensional space and vulnerable areas on equipment surface – areas with the greatest demolition potentiality are identified as well. Implementing various charge models, the protective system and the installation consisting of launch pad, spacecraft, three lightning towers and catenary wires is modelled at first and the impulse experiments are eventually performed on the lab-made model in a high-voltage laboratory. The good level of conformity observed between simulation and experimental test results verifies the above-mentioned method accuracy and application to real-size systems.

Aiming at the lack of signal preprocessing in current rectal signal research, a new 15th-order Newton iterative fast independent component analysis (FastICA) algorithm is proposed to separate the signal. To solve the incomplete problem of the single channel rectal pressure signal, C-C phase space reconstruction technology is used for multi-dimensional signal reconstruction. In order to achieve the diagnosis of rectal dynamic after artificial anal sphincter implantation, the preprocessed rectal signal component is subjected to short-time Fourier transforms for time–frequency analysis. This constitutes a complete rectal dynamic function diagnosis process. The non-stationary simulation signal is constructed to verify the preprocessing method. A complete diagnostic experiment is performed on two rectal signals of different gut dynamic. Simulation results show that the proposed method can realise the preprocessing of non-stationary signals. Through the rectal dynamic function experiment based FastICA-STFT, two different rectal signals are distinguished, and the results are consistent with the clinical diagnosis, which has achieved the diagnosis of rectal motility. This study will provide support for the recovery of rectal dynamic function in patients with artificial anal sphincter implants.

Statistical characteristics of discharge magnitude are significant for insulation diagnosis by monitoring partial discharge (PD) in power apparatuses. However, hitherto, investigations on the PD magnitude distribution in SF₆ gas under direct current voltage are insufficient. A current pulse measuring circuit and a ultra-high-frequency (UHF) antenna were simultaneously employed to investigate characteristics of positive corona in 0.3 MPa SF₆ gas. It is found that compared to the UHF antenna, the common measurement impedance used in laboratories caused several current pulses overlapped, resulting in pulse burst phenomenon. The pulse burst was easily mistaken as a single PD, which actually contained several PDs, thereby negatively affecting obtaining a real discharge magnitude distribution. Moreover, the discharge magnitude distributions were compared when a pulse burst was treated as a single PD and several PDs, respectively. It is found the former and latter one had forms of non-skewed two-parameter Weibull distribution with large-scale parameters and positively skewed two-parameter Weibull distribution with small-scale parameters, respectively. Based on this understanding, the change of the distributions with time was investigated, and the results showed that the distribution would have a permanent form of two-parameter Weibull distribution after a 24-h transition time.

The authors report some encouraging results with basis on their calculations to forecast the magnitude of anomalous thrust forces measured in resonant microwave cavities with dielectrics, for two configurations known as Cannae-Drive and Tapered Drive, when operating for high values of power. Despite of the weakness of the forces, both devices could provide us with a novel future propulsion technology by means of a thrust without ejecting propellant. In the calculations, they applied their theoretical model based on the dipole-environment interaction via generalised quantum entanglements (GQE) ensuring the momentum conservation principle. They obtain good agreement with the experimental measurements, although the anomalous forces have weak magnitude. The control and enhancement of the effect can be accomplished by applying GQE hypothesis in order to allow the future viability of a new technology based on quantum electromagnetic propulsion of aircrafts and vehicles.

Sudden changes in loading or weak constitution of power network causes power swing which may aggravate miss-operation of protective elements. Consequently, it becomes utmost essential to rapidly and accurately distinguish between fault and power swing conditions to prevent instability in smart power grid equipped with compensation. This study demonstrates an effective disturbance classifier scheme for series compensated transmission line (SCTL) for discrimination during disparity in power grid contexts using sequence-space-based support vector machine (SVM) classifier. The test data sets are generated by performing extensive simulations in PSCAD software by varying system and fault context. SVM architecture has been trained and tested by generating feature vector using modified full cycle discrete Fourier transform in MATLAB. After proper extraction of features of the interest at the time of disturbance, a decision about power swing or fault has been carried out using SVM classifiers. Regulation and kernel function parameter have been tuned using ten-fold cross-validation applied on training set. The developed scheme is also evaluated for symmetrical fault detection during power swing and shows remarkable improvement in accuracy and speed for protection of SCTL in comparison to existing schemes.

In order to satisfy the requirement of calibration precision and traceability for space remote sensor, the absolute radiance calibration primary radiometer (ARCPR) is investigated for establishing the irradiance calibration standard in orbit. ARCPR is a mechanical cryogenic absolute radiometer for space application, and works at 20 K. The cryogenic environment is obtained by the Stryn-type pulse tube cryocooler. The environment temperature is stable at 23.9658 K by high-precision temperature controllers. The detector of ARCPR is designed and investigated based on the experimental prototype. The experimental results of detector characteristics measurement illustrate that the sensitivity is 3.9526 K/mW, and the thermal time constant is 134 s. The procedure of optical power measurement is optimised for satisfying the requirements of in orbit measurement. ARCPR achieves a relative standard uncertainty of 210 ppm at an optical power level of 0.4 mW. Therefore, ARCPR could be the radiometric standard for optical measurement. Furthermore, the investigation result provides the theoretical and experimental basis for the establishment of radiometric calibration standard in orbit.

Discrimination between transient fault and permanent fault is contemporary problems for protection of transmission line. Auto-reclosure is one of the foremost solutions for the same. This study presents the development of auto-reclosure scheme using modified full-cycle discrete Fourier transform with adaptive dead time control. The discrimination between transient and permanent fault is done using differential voltage across the contacts of circuit breaker. Reclosing instance is identified by comparing absolute value of positive sequence voltage, phase difference and frequency difference with a respective preset threshold using synchronism check relay. The proposed scheme has been validated by simulating power system considering variation in fault location, fault clearance angle, fault resistance and load flow in PSCAD/EMTDC. The algorithm for the auto reclosing scheme is validated in MATLAB software. Real time emulation of the proposed algorithm is performed using AVR ATmega 328P controller on laboratory prototype. The test results of simulation and hardware emulation corroborate the efficacy of the proposed technique.

The authors investigated the effect of the insulator hydrophilic fraction on the pollution flashover performance by the up-and-down method. The hydrophobicity of parts subjected to a high electric field intensity such as two ends of an insulator, may be weakened by corona discharge. In this study, they simulated the behaviour of composite insulator surfaces at six hydrophilic fractions. Furthermore, arc discharge was recorded using a high-speed camera and the probability of arc discharge was analysed. They found that as the hydrophilic fraction was increased, the 50% probable flashover voltage first decreased and then increased. The wetting process and discharge type could be classified into two types and the flashover process could be divided into two stages by a clear hydrophilic fraction boundary through leakage current characteristic, discharge probability, and arc shape analysis. The results indicated that uneven hydrophobicity loss might lead to further flashover voltage reduction, up to 26.5% lower, than that with uniform hydrophilicity. This should be considered in transmission line design and maintenance of composite insulators.

Most sensors exhibit a non-linear input–output relationship. Sensor linearity is essential for the true representation of measurand in modern instrumentation systems. Although several linearisation techniques (LTs) have been proposed in recent years, they incur common problems of scalability, reliability, flexibility, complexity and cost. Hence, an effective software lineariser is needed to overcome these difficulties. This study presents a Takagi–Sugeno (T–S) fuzzy-based sensor LT using piecewise linearisation. The non-linear static relationship splits into ‘N’ multiple linear algebraic equations, which are combined using T–S fuzzy logic to ensure a smooth transfer from one region to another. The linearity (mean square error) of 0.1663 is obtained for negative temperature coefficient thermistor in simulation over a temperature range of 307 to 373 K, and of 0.0255 is achieved for infrared sensor in real time over a distance range of 12–30 cm. The performance of the proposed LT is compared with popular curve fitting, a look-up table and soft computing approaches. The results show that the proposed LT outperforms other approaches regarding performance indices. This technique eliminates hardware complexity rendering better accuracy over the span of measurement.

The localisation of partial discharge (PD) sources using the acoustic emission (AE) technique has attracted increasing research attention. The complicated propagation routes and wave-type conversion in power transformer can induce considerable localisation error. In this paper, the catadioptric phenomenon of AE wave propagation is explained in detail. With the incident angle varying, the wave type of the direct wave in tank wall could convert and the velocity will change accordingly. A transformer model is established in which each node refers to a suspected PD position and a shortest route search algorithm is proposed to calculate the shortest path between two nodes in this model. However, the fastest route is most significant to PD localisation rather than the shortest route when TDOA method is used. As a result, an improved propagation route search (IPRS) algorithm, which can recreate the propagation process and calculate the fastest AE routes, is proposed to localise the PD origin. To verify the feasibility of the IPRS algorithm, localisation experiments were performed in 35 and 110 kV transformers, respectively. Compared with other present localisation methods, such as the Chan algorithm, the genetic algorithm and the imperial competitive algorithm, the proposed algorithm can effectively reduce localisation error.

Partial discharge (PD) measurement is an efficient method for condition monitoring of insulation in high-voltage (HV) power apparatus. Generally, phase-resolved PD (PRPD) patterns are commonly used to identify the PD sources. It is clearly recognised that there is a correlation between the PD patterns and the insulation quality. However, in the case of multiple PDs, the PRPD patterns partially overlapped in nature, which results in difficult to identify the types of partial discharges. In this proposed methodology, a combined algorithm of different edge detection methods with box-counting fractal image compression technique is used for fractal feature extraction. The extracted features used as the input vector for the classifiers for PD recognition. To evaluate the performance of the proposed methodology, artificially multiple PD sources are simulated in HV laboratory. The result of this proposed work shows better recognition for canny edge detected fractal features implemented with user define kernel multi-class nonlinear support vector machine which can be further used to assess the insulation properties for practical implementation in power industry.

Modern electronic nose and such systems, typically employ gas sensors in arrays. Access to the individual elements in an m × n resistive sensor array requires m + n interconnect lines and effect of crosstalk becomes inevitable. The crosstalk is caused due to the leakage currents in the multiplexer channels as well as the parasitic paths among the non-selected elements in the array. Here, the authors present a novel circuit arrangement to suppress crosstalk in two-dimensional chemo-resistive sensor arrays. The proposed circuit employs a transistorised bypassing scheme, diodes in series and voltage feedback to non-selected elements of an array for crosstalk elimination. Simulation results of a resistive sensor array are presented. Finally, the proposed arrangement has been applied on an 8 × 2 sensor array and the result has been compared with the same array with a normal feedback arrangement for data acquisition. The work can also be extended for general resistive sensor arrays.

In this study, a new multi-objective optimisation model is developed to deploy phasor measurement units (PMUs) and intelligent electronic devices (IEDs) optimally in an active distribution network for state estimation. Three objective functions are considered in this optimisation problem such as the total cost of PMUs and IEDs, and the root mean square value of state estimation error. Since conflicting objectives are considered; to find the optimal locations of the devices, the meter placement problem is developed in a multi-objective framework to get compromised solution. The best compromised solution is obtained using multi-objective hybrid particle swarm optimisation (PSO)-Krill Herd algorithm (KHA). Furthermore, the reliability of the proposed meter placement technique is tested under load and generators’ output variations. All distributed generations (DGs) are considered as wind generators and the output of each DG is modelled using Weibull distribution function. The proposed algorithm is tested on IEEE 69-bus system as well as on a practical Indian 85-bus system. The obtained results have been compared with traditional PSO, KHA and also with well known non-dominated sorting genetic algorithm.

Cross-linked polyethylene (XLPE) insulation is successfully used for high-voltage AC transmission. However, it is still under development for high-voltage DC application due to space charge accumulation, which distorts the internal electrical field distribution and leads to its aging/failure. Therefore, the space charge should be measured and carefully analysed. On the other side, conductivity measurement helps to forecast the degradation probability of the insulation. Higher conductivity represents the severe degradation. Nanofiller addition, such as SiO₂, TiO₂, MgO and so on (<5 wt%), particularly surface-modified nanofiller due to its better dispersion significantly suppresses the space charge accumulation and conductivity. Nevertheless, the choice of suitable nanofiller has still remained a challenge. With this context, space charge and conductivity of XLPE-silica and XLPE-magnesium oxide (MgO) surface-modified nanocomposites are measured. This study proposes a parameter for nanofiller selection that will deliver optimal properties for the intended application. Results show that nanocomposites with higher nanofiller permittivity (i.e. MgO) have less space charge accumulation and low conductivity and are justified with the help of a band gap theory model.

This study presents results of modelling of heat transfer in low-power synchronous motors with internal permanent magnets (IPM). The analysis is conducted on the basis of equivalent thermal network as well as the magnetostatic finite element analysis for determination of usual electromagnetic loss components. The approach which consistently combines the two mentioned models allows for effective analysis of heat transfer in the machine at the designing stage. Special attention is focused on the method for homogenisation of a mush-wound winding and sheet stack. The results of computer simulations are positively verified by measurements carried out on the physical motor.

In this study, the prediction of the breakdown probability of a new batch of nanofluid (NF), namely exfoliated hexagonal boron nitride based NF is performed. Weibull two-parameter model distribution function has been used to predict the AC breakdown voltage (ACBDV) probability percentage at 5, 10, 50 and 63.2% of failure. To verify the effect of ageing on the other allied properties like dielectric dissipation factor, resistivity, interfacial tension, acid number and thermal conductivity of the insulating NF, oxidative ageing test has been performed at three different ageing durations and compared with the existing mineral oil (MO). It is observed that the new batch of NF has the superior properties to be new age insulating oil compared to the MO. A significant enhancement in the ACBDV and thermal conductivity of the NF compared to MO is observed. Hydrophobic nature of the nanoparticle (NP) which has the minimum affinity towards the polar contamination hinders early ageing degradation in the NF. The enhancement in ACBDV of NF is due to the stimulated charge accumulation on the surface of the NP of the NF. The high aspect ratio of the exfoliated NP surface enhances the heat transfer capabilities in the NF.

Polymer composite insulators acquire the position of their counterpart ceramic and glass insulators in high voltage overhead transmission systems due to their remarkable pollution performance. They have different potential and electric field distributions compared to that of ceramic insulators and the absence of intermediate pin and cap metal fittings makes them compact in size by reducing the distance between energised and grounded ends. This study presents a simulation-based approach to compute the streamer propagation characteristics in polymer suspension insulators under positive polarity lightning impulse voltages. The streamer inception, propagation, and sustenance criteria are evaluated using finite element method-based electric field computations. The significance of insulator geometries on streamer inception and propagation phenomena is well established. The insulator geometries such as weather sheds, location of the first shed, and shed radius have shown a strong influence on streamer inception and propagation path, which govern the flashover characteristics of the insulator. The lightning impulse flashover voltages of different insulators were determined experimentally to validate the computed results. A good agreement is found between simulation and experimental results.