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The occurrence of lightning strokes due to indirect effect of lightning discharges, has assumed a lot of importance in the recent times. This is due to the sensitive, vital electronic equipment which are highly vulnerable to such indirect effects. In this article, attempts are made to bring out the salient features and related parameters of lightning discharges (with specific reference to indirect effects). Glimpses of the experimental research efforts to understand the phenomenon are described based on the published scientific work, along with some of the typical simulation results of the authors. These simulation results (computed electromagnetic fields) are validated by some of the important results described in the literature. This being a review article, the vital electrical and electronic systems/components which have been researched with reference to indirect effects have been enumerated, and the present understandings have been discussed.

An attempt is made to reduce the maximum value of rms electric field (E-field) via the transposition of conductors in a 765-kV substation with reference to the occupational exposure. The method is applied to a extra-high-voltage substation, which is under construction. The effect of transposing the bay conductors (alone) and the bus conductors (alone) on the E-field distribution (at 2 m above the ground) over the area of the substation is discussed. Also, the topology of substation conductors that results in the minimum value for the maximum of rms E-fields is obtained via simultaneous transpositions of the bus and bay conductors. The area of the substation where the rms E-field exceeds the reference value of 10 kV/m (International Commission on Non-Ionizing Radiation Protection occupational exposure limit) is also reported for the existing topology. For this topology, the computed maximum value of the rms E-field over the area of the substation is 13.06 kV/m. This E-field is reduced to 7.999 kV/m with the best configuration of substation conductors obtained via transposition. The charge-simulation-method-based generalized algorithm for obtaining the best topology (among all permutations) of substation conductors, which results in the minimum value for the maximum of rms E-field magnitudes over the substation area is also reported. [ABSTRACT FROM AUTHOR]

The combined acoustic-electrical system is used in the factory or plant environment for the partial discharge (PD) source localization in power transformers. A noniterative method for this combined acoustic-electrical PD-locator-system is devised and presented in this paper for the first time. It employs three acoustic emission (AE) sensors. The proposed method is compared with the existing noniterative method used in the all-acoustic system, which employs four AE sensors. The comparative study shows that the proposed method can locate the PD source irrespective of its position within the tank, whereas the prevailing noniterative method for the all-acoustic system fails to locate the PD source at certain positions within the tank. The effect of the sensor positioning on the performance of the method is studied, and some guidelines for the sensor placement on the transformers tank wall in a factory or plant environment are suggested. The proposed method is also applied to the data taken from the published literature. The localization results are compared with those of an existing iterative method (Newton's method) to prove its superiority in terms of computational time. [ABSTRACT FROM PUBLISHER]

With the increase in transmission voltage level, and the guidelines of the International Commission on Non‐Ionising Radiation Protection (ICNIRP), the effects of non‐ionising radiation on biological elements at high‐voltage substations have gained significant importance. The electric field (E ‐field) distribution in an upcoming 765 kV substation in the Indian subcontinent is computed using the charge simulation method (CSM). CSM is used to model the 765 kV bays, transmission lines, buses, and ground wires in the substation. The three‐dimensional (3D) E ‐field is calculated through the superimposition of E ‐fields obtained in two orthogonal planes using infinite‐line charges. This proposed method of using infinite‐line charges gives realistic results. The simplistic model using infinite‐line charges greatly reduces the complexity of the CSM‐based model (due to the reduced number of charges) apart from increasing the CSM‐based model accuracies. This fact has been demonstrated by comparing these results with those of CSM‐3D‐model of a detailed bay model (including major equipment and associated support structures). The complex‐charge‐based CSM helps in computing the root mean square value of the E ‐field at a point, directly, as per ICNIRP guidelines. This RMS value of the E ‐field is compared with the occupational exposure reference value prescribed in the ICNIRP guidelines. [ABSTRACT FROM AUTHOR]

Standard capacitors form an important component of the measurement and instrumentation in the electrical laboratory. A high‐voltage (HV) standard capacitor of 100 pF, 12 kV (rms) is designed using the charge simulation method (CSM). CSM is a semi‐analytical method and it provides inherent advantage in designing a capacitor from the first principle. The capacitance is obtained from the magnitude of the simulating charges of the CSM‐based model and the corresponding potential. The design details of HV standard capacitor are discussed along with the analysis of the potential and the electric stress distribution. The electric stress everywhere in the capacitor, which is designed, is assured to be <5 kV/cm, which was set as the limiting (maximum permissible) stress. The capacitance of the fabricated unit is measured in the HV laboratory. The CSM‐based result of the capacitance of the designed HV capacitor agree well with the results of the laboratory experimental measurement. The inherent advantage of CSM in designing a capacitor is confirmed by comparing with the results of method of moments (MoM). [ABSTRACT FROM AUTHOR]

The key problem in locating a source of partial discharge (PD) using the acoustic emission technique is the error in estimating the signal arrival time from the source to the multiple sensors. When the time difference of arrival approach is used for the PD‐source‐localisation, some of the measured time‐delay‐groups will have solution for the time‐difference equation in the complex‐number‐field. This is due to the significant error in the arrival time estimation. Such time‐delay‐groups should be considered to be invalid. In this study, a function is proposed for identifying the invalid time‐delay‐groups for the fixed set of coordinates of four sensors and the specific velocity of the acoustic signal used. The negative sign of this function value indicates that the solution is in the complex‐number‐field. An alternative method for identifying the invalid time‐delay‐groups is by using Newton's method. The multiple sign changes of the Jacobian‐determinant in the iterations of Newton's method shows that the solution is in the complex‐number‐field. The proposed methods have been tested with data from the existing literature, and results have confirmed the efficacy of these methods in the identification of the invalid time‐delay‐groups. Discarding such groups of time delays improves the accuracy of statistical PD‐source‐localisation. [ABSTRACT FROM AUTHOR]

Back-to-back switching of 50 kVAr capacitors, in a capacitor bank of 200 kVAr is investigated experimentally. The switching inrush currents in a three-phase, 200 kVAr, 415 V Automatic Power Factor Correction panel at power frequency are captured in the laboratory. The characterizing features of inrush current are reported and analyzed. The commercially available two makes of switches (contactors) are used to compare the inrush currents with and without their pre-insertion resistors (PIR). The inrush current scenario of the experimental setup is modeled in EMTDC/PSCAD to ascertain the results. The ratioIpeak/INfor both the contactors without PIR exceeded the limit mentioned in IEC 60831-1 Ed 3.0 : 2014. [ABSTRACT FROM PUBLISHER]

The behavior of partial discharge (PD) acoustic emission (AE) signals in the transformer oil for a temperature range of 30–75 °C is studied via laboratory experiments. The AE signals are analyzed using the fast Fourier transform (FFT) to obtain the peak frequency and the AE amplitude. A peculiar behavior of reduction in the peak frequency and the AE amplitude observed above 65 °C is reported. An attempt is made to explain the reduction in the AE amplitude after a certain temperature by correlating it with the properties of the transformer oil such as the viscosity and the breakdown voltage. This AE signal analysis is perhaps an important advancement in the PD diagnosis and the PD spectrum analysis at different temperatures in the transformer oil. [ABSTRACT FROM AUTHOR]

• Multi-objective GA-CSM based algorithm is proposed, for the first time, to identify the optimal ground clearances of EHV substation conductors for adherence to the ICNIRP guidelines. • CSM models are developed as per the actual layout of the substation and E-fields are computed in view of occupational exposure. • Modified ground clearances are obtained for the existing conductor arrangement and for the best topology among the transposed topologies. • Novel substation layout with reduced inner bay heights is proposed. The magnitude of the electric field (E-field) in a 765 kV substation is reduced by altering the conductor clearances in view of the occupational exposure limits. Multi-objective genetic algorithm (GA) along with the charge simulation method (CSM) is utilized in arriving at the optimal clearances of the substation conductors. An EHV substation is modeled with the dimensions and the clearances as in the actual layout of a substation. The E-field results obtained using the finite-line based modeling and infinite-line based modeling of conductors, are compared in terms of the model accuracy and the computational time. The advantages of using the infinite-line based CSM model in view of the occupational exposure is detailed. With the proposed GA-CSM routine, the maximum value of the E-field in the substation is reduced to 10 kV/m (from the existing value of 13 kV/m). The proposed method is used with the existing topology and the best possible transposed topology to obtain the modified layouts. A novel EHV substation layout with different ground clearances for the inner bays and the outer bays is presented. The GA-CSM routine proposed in this work is applicable to any EHV substation with the multiple conductor arrangements. [ABSTRACT FROM AUTHOR]

A genetic algorithm (GA) is applied to calculate the lightning current parameters of the channel-base current function. Heidler’s function parameters for subsequent return stroke are tuned for a typical value of I_m (\approx 12 kA) for different (di/dt)max and also for a typical value of (di/dt)max (\approx 40 kA/\mus) for different values of I_m, using a GA as the tool. This is a first of its kind attempt to show that a GA can be used for identifying Heidler’s function parameters (as adopted by IEC Standard 62305-1, 2006) to easily obtain the required lightning current wave shape. The data are thus generated and reported (including the extreme cases) in this paper that are thought to be useful in modeling lightning channel-base currents. Further, this approach will be useful in research related to the radiated lightning electromagnetic pulse and its coupling with nearby objects. [ABSTRACT FROM PUBLISHER]

The literature on lightning stroke severity indicates that the magnitude of the electric field peak due to the firstreturn- stroke is nearly twice that of the field peak due to the subsequent return stroke. These reports are based on the data collected by lightning detection, and information and field measurement systems. In this paper, field results from the literature are summarised. These are then compared with the results obtained through simulation. Electromagnetic fields generated due to "typical" first (FS) and subsequent (SS) lightning return strokes have been computed using the "Modified Transmission Line with Linear current decay" (MTLL) model. These simulation results are discussed, keeping in view, the field data reported in several recent studies, which compare the severity of first and subsequent-return-strokes. The MTLL based engineering model is adopted to compare the severity of lightning return strokes (FS/SS) as a function of radial distance. The effect of worst-case-ground-conductivity on this ratio is reported. An MTLL model based comparison on emfield FS/SS ratiofor both perfect and worst-case-ground conditions is also reported. These simulation results are compared with those from the "Modified Transmission Line with Exponential current decay" (MTLE) model. In general, the present simulation results not only substantiate the fact that the FS/SS ratio is nearly two times, but also assess a few parameters responsible for low FS/SS ratio (reported in some cases). The present simulation analysis shows that terrain electrical conductivity affects the FS/SS ratio. This may explain the cause for the low FS/SS ratios. [ABSTRACT FROM AUTHOR]

Analysis of channel base current functions with specific reference to new channel base current (NCBC) function is reported. The main concern has been of adjusting the maximum time rate of change of lightning current (di/dt)max along with time to crest t_m. A new ratio (maximum time rate of change of lightning current (di/dt)max by average time rate of change of lightning current (di/dt)avg) has been defined. The critical numerical value for this ratio is identified as 1.7 for NCBC function. The performance of NCBC function is compared with Heidler’s function in the wave front region. [ABSTRACT FROM AUTHOR]