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To locate and read the complex pointer meter dial for the images with uneven illumination, blurred dial, and tilted dial, this paper firstly proposes an improved BRISK‐FREAK algorithm for dial position. Then, combined with the Line Segment Detector (LSD) algorithm, an automatic identification method for complex pointer meter is proposed. The dial of a large number of SF6 complex pressure pointer meter images are located and the results reveal that the proposed improved BRISK‐FREAK algorithm has good adaptability under strong interference. The computational speed of the proposed algorithm is 33% and 17% higher than the Scale‐Invariant Feature Transform (SIFT) algorithm and the Binary Robust Invariant Scalable Keypoints (BRISK) algorithm respectively. The positioning success rate of the proposed algorithm is 40%, 64%, and 32% higher than that of the SIFT, Oriented FAST and Rotated BRIEF (ORB) and BRISK algorithms respectively. The reading success rate of the proposed method is 94.5%, which is 19.5%, 39.9% and 14.8% higher than that of the methods based on the ORB, SIFT and BRISK algorithms respectively. It is particularly suitable for application in the actual substations to realize the identification of complex pointer meters. [ABSTRACT FROM AUTHOR]

The protection of traditional high‐voltage capacitor banks relies on an unbalance relay which operates when an internal fuse is blown. However, the unbalance relay cannot indicate the cause of the fault. Thus, an operator wastes time and human resources investigating the fault issues. In this paper, a fault which occurred in a 230‐kV power system of Electricity Generating Authority of Thailand was observed by performing simulations using the Power Systems Computer Aided Design (PSCAD) program. The study system based on the double bus station and 72 MVAR capacitor banks was installed in the form of a back‐to‐back topology. Three scenarios were considered: normal condition, fault occurrence in one capacitor bank and fault occurrence in both capacitor banks. Current characteristics such as the current phase and difference in unbalance current were considered. In addition, discrete wavelet transform was applied to solve the ambiguity of current generated from the PSCAD. The authors' results suggest that identifying fault events using a coefficient of wavelet is more efficient than relying on the current amplitude. The findings mentioned in this paper can be applied in a traditional power system protection scheme to enhance a system's reliability. [ABSTRACT FROM AUTHOR]

Several studies for partial discharge (PD) pattern recognition using artificial neural network (ANN) were reported in the early 1990s. Usually, in an actual field such as a substation, data on partial discharge is scarcely available, or even rare. In many cases, the power supply phase required for the PRPD pattern cannot be easily obtained. We propose an ANN method that shifts the phase in which the maximum signal intensity detected with PD sensors is generated and used it as training and input data, even for the few phases resolved PD data available in the field. This ANN method was applied to the PRPD pattern obtained in a practical field. As a result, it was shown that the discrimination rate between PD and noise was improved, and therefore the proposed ANN method was found to be effective. [ABSTRACT FROM AUTHOR]

Secondary direct-current loss within a substation is a severe event. In China, each line protection device is generally powered by one set of secondary direct current (DC) power system within a substation of 110 kV voltage level. In this case, the line protection devices will be immediately taken out of service when the secondary DC is lost, and the lines protected by them will lose their corresponding protections. Once a fault occurs on the line, only the remote back-up protection can be relied on to isolate the fault, which expands the fault influence and increases its clearance time. To handle the above problem, a novel wide-area protection algorithm based on compensation voltage moduli comparison is proposed, which is independent of multi-terminal data synchronism. Then, a comprehensive protection strategy composed of the proposed protection algorithm and the original local distances protection is proposed. The results from a power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC)-based simulation verify that the proposed protection algorithm has higher sensitivity. The comprehensive protection strategy could cope with most line faults effectively, even if only partial data are available, the selectivity and speed of which are better than that of distance protections. [ABSTRACT FROM AUTHOR]

This study presents a non‐intrusive sensing method to obtain the phasor of system voltage of overhead lines for a mobile partial discharge diagnostics platform; with the phasor, partial discharges detected by the mobile platform can be characterised by statistical phase‐resolved patterns. Firstly, finite‐element analysis simulations were conducted to understand the relations between overhead lines of different configurations and the electric field underneath. With an electric field sensor, the phasor of system voltage can be derived with the aid of a second measurement unit for system frequency. The two measurement units are synchronised by two GPS receivers with 1 pulse per second (PPS) accuracy. The method is based on the wide area measurement principle and was verified by laboratory experiments. Then, the methodology has been deployed in the 132/275/400 kV substation and underneath single‐circuit overhead lines in the field. The phasor of system voltage on an overhead transmission line can be successfully derived, and phase‐resolved partial discharge information can be calculated. This non‐intrusive and mobile methodology is effective and efficient for practical field measurements. The method eliminated the needs of connecting to an on‐site system voltage, and this is of great importance for diagnostics research carried out by mobile platforms. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Partial discharge (PD) detection and location based on ultra‐high frequency (UHF) sensor array have been employed for the power equipment in the whole substation for assessing the insulating condition of electrical equipment and determining a precondition for further implementing insulation diagnosis. At present, one of the widely used localisation methods is time difference of arrival (TDOA) based, localisation result of which is extremely sensitive to time delay estimation and usually time‐consuming to solve. Motivated by this, a data‐driven method using the deep neural network (DNN) is proposed in this study to significantly speed up the solving process of non‐linear TDOA equations and simultaneously guarantee the accuracy of results. It works with sequences of time delay measured from the UHF sensor array as the input of the network and with the corresponding coordinates of PD source as output to train the network. Simulation results demonstrate that the proposed method shows relatively higher accuracy and efficiency in PD location. In addition, many factors such as array shape, error type added to time delay, and detailed structure and parameters of network are taken into consideration for error analysis, laying foundation to more reliable localisation of PD. [ABSTRACT FROM AUTHOR]

In this paper, the overvoltage distributions due to the lightning stroke are analyzed for a 500 kV hybrid OHTL‐Cable‐GIL circuit beside substation, in which the section length is variable. Corona effect is incorporating in order to estimate the attenuation and deformation of overvoltage's travelling waves on transmission lines near substations. The influence of connecting substations surge arrester, direct, and indirect lightning strokes are investigated. ATP/Electro Magnetic Transients Program(EMTP) simulation program is applied to analyze the lightning overvoltage of a 500 kV hybrid OHTL‐Cable‐GIL system. It was discovered that OHTL‐Cable, OHTL‐GIL, and hybrid systems produces lightning overvoltages higher than those of a fully cable system and very likely lower than those of a fully OHTL system with the same transmission lengths. This means that the risk of experiencing high lightning overvoltages and stressing system components is higher in a fully‐Overhead Line (OHL)circuit than in a partial or full cable or GIL line. Furthermore, using the Cable with MOSA (Metal Oxide Surge Arrester), the results have more regular voltage waveform at substation entrance; also Hybrid line has the same effect of fully GIL. Finally, the corona has a less attenuation effect of overvoltage reached to substation by about 2.7% in case short length OHTL. [ABSTRACT FROM AUTHOR]

Transient electromagnetic (TEM) method is a reliable means of non‐destructive testing for fault diagnosis of grounding grid in substation. In view of the small transmitter loop of the TEM system and many measuring points and survey lines of grounding grid detection in substation. This study presents a fast solution to TEM apparent resistivity imaging for grounding grid detection using artificial neural networks. The input ‐output mapping relation of neural network is established based on TEM response characteristics of the grounding grid. The built network could map the recorded TEM data of grounding grid detection and quickly obtain the resistivity image. The proposed method offers accuracy and fast computation for the resistivity imaging of grounding grid. Feasibility and technical attractiveness of the proposed method in fast imaging of apparent resistivity is investigated with the measurement of grounding grids in the actual substations. It can be used in real time so that the recorded TEM data in substation can be calculated without re‐training, which avoids time‐consuming inversion computation. The rapid processing of massive data and submitting the detection results of the grounding grid to customers rapidly and in real time, which is expectation for a modern power industry. [ABSTRACT FROM AUTHOR]

This study describes a key element of any modern wireless sensor system: data processing. The authors describe a system consisting of a wireless sensor network and an algorithmic software for condition‐based monitoring of electrical plant in a live substation. Specifically, the aim is to monitor for the presence of partial discharge (PD) using a matrix of inexpensive radio sensors with limited processing capability. A low‐complexity fingerprinting technique is proposed, given that the sensor nodes to be deployed will be highly constrained in terms of processing power, memory and battery life. Two variants of artificial neural network (ANN) learning models (multilayer perceptron and generalised regression neural network) that use regression as a form of function approximation are developed and their performance compared to K‐nearest neighbour and weighted K‐nearest neighbour models. The results indicate that the ANN models yield superior performance in terms of robustness against noise and may be particularly suited for PD localisation. [ABSTRACT FROM AUTHOR]

Primary equipment failure in substation has a significant impact on the reliability of the power supply, and even threatens the thermal stability of power grid. This study presents a method identification of electrical connectivity and thermal stability assessment of power grid after primary equipment failure. The identification method of electrical connectivity based on incidence matrix provides a way to determine load curtailment after equipment failure. Subsequently, the inject power of substation bus in power grid is modified by load curtailment. Moreover, based on the DC power flow model, the active power flow distribution of power grid is calculated, which is used to evaluate whether the active power of lines exceeds limit. Compared to the traditional N − 1 assessment method, this method not only has the advantages of fast calculation and strong pertinence but also of convenience for the field application. [ABSTRACT FROM AUTHOR]

Power system measurement is extremely crucial for the stable power system operation and results in the generation of bulk data. This enormous volume of data must be transferred from field devices to the control centre and must be preserved for future references. Analysis of practical generation scheduling and monitoring data indicates its repetitive and slow varying nature. A simple, low‐computational compression algorithm, the differential binary encoded algorithm (DBEA), is developed for compressing such information and a high compression ratio is achieved for the majority of practical data sets. To overcome the constraints of the DBEA, extended version of DBEA (E‐DBEA) is developed which increases the range of input at the expense of compression ratio. Resumable load data compression algorithm (RLDA) is a differential coding‐based algorithm developed for compressing load profile data. Comparison of the performance obtained by the DBEA, E‐DBEA and RLDA with practical data sets clearly indicates the effectiveness of the DBEA and E‐DBEA. The online test bench of the DBEA and E‐DBEA consists of two inter connected PCs, one working as virtual load despatch centre and other as virtual generating station or sub‐station. Due to the simplicity of the proposed work, it can be useful for data storage and data transfer both at high‐level PCs and low‐level microcontrollers. [ABSTRACT FROM AUTHOR]

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]

Nowadays, a strong concern to decrease greenhouse gas emissions is encouraging the implementation of renewable energy sources closer to end‐users, in low‐voltage (LV) distribution networks. Due to the expected high microgeneration (µG) penetration level, several problems are likely to arise, such as overvoltages and reverse power flow. This study presents a review of the several techniques used to deal with these problems. These are compared in terms of their capacity to smooth the voltage profile and avoid reverse power flow. An unbalanced three‐phase power flow algorithm, based on current summation method for radial distribution networks, is proposed. A study based on a highly unbalanced test radial LV distribution network for a typical summer day, with a high µG penetration, is performed. The voltage profile, active power flow in the service transformer, and power losses on the network are the monitored electrical quantities. The obtained results indicate that self‐consumption with storage is the recommended solution to eliminate overvoltages, to avoid reverse power flow and allow for a decreasing in the power losses. Nevertheless, the economic viability of this solution must be carefully assessed, because the profitability of the project is not straightforward at the current time. [ABSTRACT FROM AUTHOR]

Changing dynamics of power systems caused by the migration from conventional to distributed energy sources increase the risk of blackouts due to voltage instability, especially in case of unforeseen network conditions (e.g. (N‐k)‐cases). To enable both secure and efficient power supply, novel monitoring and emergency control systems for the identification of voltage emergency situations as well as the execution of control actions are required that react reliably in due time and adaptively in the case of changing network situations. This study presents a distributed agent‐based approach to counteract voltage instability that is based solely on local measurements and limited inter‐agent communication. Distributed agents located at substations in the (sub‐)transmission network monitor distribution and transmission voltages, as well as, load tap changer positions and are able to autonomously curtail load in case system stability is endangered. The applicability of the approach is demonstrated in a co‐simulation environment interfacing the multi‐agent system with a dynamic power system simulation. The presented approach allows for an early detection of voltage instability as well as a coordinated execution of available control actions. [ABSTRACT FROM AUTHOR]

The potential benefits of direct current (DC) network in low‐voltage system promote smart grids and facilitate increasing penetration of distributed generation (DG). Correct identification of faulted section of a distribution network by an automation system reduces power outage time and improves reliability indices of such systems. With the onset of a fault in a DC distribution system, data recorded at an outage management system are used to identify the faulted section. With DG units active in a distribution system, there will be bidirectional power flow and faulted section identification becomes challenging. Using voltage and current data from consumer‐end smart meters and the substation, a method is proposed to identify the faulted section in DC distribution system. The Hadamard product of fault‐affected sections (obtained from network topology and voltage status matrices) is used to identify the faulted section correctly. Using power systems computer‐aided design/electro‐magnetic transient design and control simulation, the accuracy of the proposed method is verified for different fault situations including simultaneous faults, fault close to a bus and with rooftop photovoltaic integration to a DC distribution system. The method has the capability to provide information on the fault segment that connects feeder pillar to the consumer end also. [ABSTRACT FROM AUTHOR]

Reflected wave identification is the core of single‐ended travelling wave fault location, in which the obvious superimposed oscillation is the main obstacle for precise reflected wave identification with field data. This study proposes a reflected wave identification method based on speeded‐up robust features, which can gradually approximate from the possibly largest fault distance to the near‐end fault distance so as to exclude the reflected wave from time window containing initial wave. In particular, the time window segmentation divides initial wave and reflected wave into two inconsistent time windows, hence the reflected wave from the superimposed oscillation that usually follows the travelling wave can be effectively separated, such that the identification of reflected wave can be significantly simplified. Lastly, the superimposed oscillation is thoroughly analysed while both the field data with and without obvious superimposed oscillation are presented to evaluate the effectiveness of the proposed approach. Field data obtained from 21 substations scattered among Yunnan power grid of China validate the implementation feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Ultra‐high frequency (UHF) technique is chosen for partial discharge (PD) detection due to its excellent anti‐interference and stability. The existing UHF PD localisation methods are mainly based on time‐difference technique, that suffer high hardware cost due to the high sampling rate requirement. The wireless UHF sensors together with the scene analysis methods, i.e. received signal strength indicator (RSSI) fingerprint, provide us a low hardware cost and high environmental adaptability solution for PD localisation in substation. The proposed PD localisation method here is divided into two stages. In the offline stage, the RSSI fingerprint map is established by site survey. In the online stage, the position of PD source is estimated by a probabilistic approach. To reduce the influence of noise, the RSSI fingerprints are transformed to a low‐dimensional subspace, while the most of redundant noise is discarded. Furthermore, the PD heterogeneity and interference in the offline stage are also discussed and solved by normalisation and clustering algorithm, respectively. A filed test is performed and the results indicate that the mean localisation error is 1.87 m and 82.6% localisation errors are <3 m. The workload in the offline stage is also reduced ∼50%. [ABSTRACT FROM AUTHOR]

This study describes a solution to discriminate the original sources of bad data which are concerned by the substation maintainers. Bad data caused by defects of monitoring system, such as mal‐setting of monitoring devices or time skew, are concerned here. These bad data can be identified mostly in electric power control centre by bad data identification (BDI) methods including robust state estimation; however, these methods can hardly explain the relevant original sources of bad data in substations. Here, the authors propose a data‐driven method named abductive identification (AbI) to discriminate the original sources of bad data already identified by BDI methods. In the AbI method, feature patterns of bad data, based on their residuals, are investigated. A feature pattern selection method for bad data is then proposed, in which both the absolute residual and relative residual are considered. Based on this feature selection approach, a Bayesian classifier is developed to identify the original sources of bad data. A two‐level architecture for the AbI approach is introduced to deal with diverse bad data patterns of wide‐area networks. Simulation and field test results demonstrate the applicability of the proposed method. [ABSTRACT FROM AUTHOR]

Since failure of high‐ to medium‐voltage (MV) transformers affect a large number of consumers, they are usually built with a redundancy to guarantee service restoration in the case of a single contingency. The redundancy can be provided by a backup transformer or by transferring the load to a neighbouring substation in case of failure. While a load transfer allows for more efficient use of transformers in normal operation, it also requires the MV network to be dimensioned with redundant transmission capability for the contingency case. In this study, the authors present their approach to determine if it is profitable in the long term to remove a backup transformer in intrinsically safe substations and handle resupply with load transfer to neighbouring substations instead. To this end, they compare the cost of the necessary network expansion to the costs of a backup transformer. They introduce an iterated local search algorithm for the calculation of emergency switching plans as well as expansion of the MV network. The methodology is applied to a large real MV network group, where reinforcing the network to allow a load transfer is cost efficient compared with the existing backup transformer in three of four substations. [ABSTRACT FROM AUTHOR]

The ultra‐high frequency (UHF) partial discharge (PD) monitoring is one of the most effective ways to detect the insulation failure in electrical equipment. Although the UHF method avoids the intensive low‐frequency noise, various electromagnetic interferences in substation can still influence its effectiveness and reliability. Most existing denoising algorithms, however, are unable to suppress different kinds of noise simultaneously. Meanwhile, the main focus of these algorithms is on the degree of noise reduction, while pay little attention to feature preservation. Therefore, a novel denoising method namely optimised variation mode decomposition and wavelet (OVMDW) is developed in this paper. In OVMDW, an optimised variational mode decomposition (VMD) algorithm is presented firstly to decompose the original signal into several band‐limited modes. Then, a determination rule is designed to identify the effective components from these modes. Finally, the wavelet‐based denoising method is employed to remove the residual white noise. Denoising results for simulative and experimental data show that the proposed method can remove various interferences from UHF PD signals. Additionally, new indexes are introduced to evaluate the performance of denoising algorithms in practical situations. Comparison results based on these indexes reveal that the proposed method using the VMD approach can preserve quite well the features of original signals. [ABSTRACT FROM AUTHOR]

State of Health (SOH) is one of the most important parameters of lead-acid batteries. Most of the existing SOH estimation methods only take the influence of charge cycles into consideration, and the estimation accuracy is limited. Batteries in the substations have two typical states: one is the check-discharge state, in which the batteries are discharged for 8 h at 0.1 C (Capacity) to determine whether the battery pack has certain reliability. The other is the floating charge state, in which the batteries are connected to the charger to maintain full power. This paper proposes a novel SOH estimation method based on the two states. In the check-discharge state, the relationship between the voltage and the age of battery is analysed. The health index, which is introduced in this model, is affected by the age of battery. In the floating state, the relationship between the internal resistance and the age of battery is discussed. Another SOH model is established based on the change of the internal resistance. By combining the two models, the estimation method can achieve real-time estimation and high accuracy for substation application. An accelerated life test is applied to verify the theoretical analysis. The experimental results demonstrate that the SOH estimation error is less than 3% which is very satisfactory for practical applications. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To research the magnetic field interference on cables nearby three-phase air-core reactors and the shielding effect of different materials, this study analysed the influence on spatial magnetic field by using high-conductivity materials and high permeability materials after the basis of three-dimensional electromagnetic simulation model, and analysed the causes. Furthermore, the induced voltage in different shielding methods is calculated and discussed by using magnetic vector potential resulted from the finite element method. From the result, to achieve a satisfying effect, the shields under three-phase reactors need connect when using high permeability. Moreover, a large number of magnetic leakages on the edge of shield can aggravate the magnetic field interference in surrounding areas. Therefore, the distribution of onsite cables in substation need to be considerate when using high permeability. [ABSTRACT FROM AUTHOR]

Electromagnetic Transient Programme has been used to calculate the lightning intruding wave of 550 kV GIS substation. The effects of mode operation, surge impedance and length of cable have been considered in the process of calculation. Besides, the corresponding protection scheme has been proposed on the basis of the results of calculation. Results of the research show that when the system is operating in single-in-single-out way, the voltage intruded into the substation is highest; the bigger of surge impedance for GIS, the higher of the voltage; the overvoltage amplitude decreases with the increase of the length of the cable; the installation of metal oxide arrester (MOA) at the entrance of GIS and the region close to the transformer or using the reactor instead the arrestor at the entrance of GIS can limit the voltage strike on the transformer effectively. [ABSTRACT FROM AUTHOR]

In this study, an aging identification approach is proposed for capacitive voltage transformers (CVTs). Aging is an unavoidable phenomenon which emerges and spreads in equipment structure and mainly affects the insulation parts. The aging may affect transformer output in its primary stages. If it grows, it may cause serious damages to the equipment, substation and the staff. Accordingly, it is necessary to diagnose the aging of CVTs in its primary steps in order to implement the required maintenance and repair. The proposed aging identification method is an efficient method which collects data from different sources in digital substations to diagnose aging in CVT structures. Moreover, the possible external disturbances are also taken into account. A modified method is proposed based on the distance between the evidences. In addition, the algorithm is capable to identify the CVTs providing bad data arising from their aging. [ABSTRACT FROM AUTHOR]

Research of switching operation transient electromagnetic field in substations is fundamental to the protection of mine monitoring systems against electromagnetic interference. Three models, which are the equivalent circuit of switching on/off inductive load, transient radiation of short dipole, and transmission line of long cable, are built for numerical analysis. The results indicate that switching operation does not produce transient pulse when the breaking angle is close to 90°. Electric fields are the primary form of transient pulse radiation, and the effect of the magnetic field on the environment can be ignored. Long cables are naturally resistant to differential mode transient pulse propagation, but the effect of common mode transient pulse cannot be ignored. Energy distribution of transient pulse in different frequency ranges is calculated by using theParserval equation. Furthermore, the measurement frequencies and the instruments used in the coal mine are determined, and on‐site data is then obtained. Measurement results show that switching operation may produce a series of transient pulses, causing the electric field to grow larger than before. Specifically, conducted emissions have large impacts on the monitoring circuitry of the mine equipment, causing the mine monitoring system to frequently record erroneous data and omit information. [ABSTRACT FROM AUTHOR]

The accuracy of switching overvoltage measuring system is significantly affected by the input impedance of oscilloscope. First, the principle of switching overvoltage is presented, followed by a brief introduction to the structure of measuring system. Using the laplace transform, the transfer function of the measuring system is then derived. Its frequency response, ranging from DC to 1 GHz, is investigated in detail. The influences of the input impedance on the amplitude and phase angle responses are clearly revealed. Two typical cases, i.e. unit step response and sinusoidal step response, are also considered in the study. To validate the above analysis, a series of experiments has been performed at a substation. Both the theoretical analysis and the experimental results indicate that the input impedance affects the accuracy of switching overvoltage measuring system significantly. In the case that the impedance is rather small, the voltage waveform displayed on oscilloscope would be considerably distorted from the one stressed on the line. The impedance should be greater than 107 Ω to satisfy the accuracy requirement. On the other hand, it can be also used as a direct indicator to assess the performance of oscilloscope. [ABSTRACT FROM AUTHOR]

Regenerating trains are now in common use on many DC fed railway systems, and train operating companies are able to get a discount on their energy costs if regeneration is active. The electrical energy consumption in a DC system is significant, and a comprehensive understanding of how regeneration affects the overall system energy consumption has not been developed. This study presents a simulation method in which a multi‐train analysis is used to determine the system energy consumption with and without regeneration in operation, as well as the impact on the system energy consumption of different headways. The results are used to determine a full 'energy audit' of the system based on the data of the Beijing Yizhuang subway line. This includes the energy supplied by the substations, the energy wasted in the power transmission network, the energy used by the train in traction and regenerated by braking trains. The initial results show that regenerating trains have a significantly lower substation demand, but slightly more energy is lost within the network. The results also indicate that, the available regenerative energy and total substation demand vary with different timetables, and there is a 27% difference between the best and worst headways. [ABSTRACT FROM AUTHOR]

This study addresses the problem of determining which non‐linear loads can be considered potential harmonic sources to the voltage harmonic distortions observed in the utility grid voltages. Statistical regression models are used to establish correlations between the simultaneously measured harmonic voltages, in the grid, and harmonic currents, at each non‐linear individual load. First, the R‐squared statistic is used to decide the goodness of fit of the developed models, giving indication on the relevance of the model. In order to overcome the limitation of the linear regression model based on voltage and current magnitudes measurements only, that imposes a constant behaviour for the background harmonic sources, a non‐parametric regression model is suggested and a comparison between the performances of the two models is carried out. Field data from two real electrical systems, one having a 138 kV substation in which a large industrial load and a 34.5 kV rural long feeder are connected; and the other having four urban 13.8 kV feeders supplying industrial and commercial loads, were used to develop and validate the statistical models used in the application. [ABSTRACT FROM AUTHOR]

A new algorithm for busbar protection is proposed based on the Hilbert–Huang transform in this study. The algorithm decomposes currents of all lines connecting to the busbar into intrinsic‐mode functions and calculates the instantaneous amplitude of the first intrinsic mode function (IMF). Then, the instantaneous amplitude is normalised to eliminate the impact of fault initial angle and transition resistance. When a fault occurs on the busbar, the initial travelling waves on head ends of the lines all have great instantaneous amplitudes; when a fault occurs on any line, the travelling wave on the faulted line is of great instantaneous amplitude, whereas the initial travelling waves on healthy lines are of small instantaneous amplitudes. Thus, through analysing the detected instantaneous amplitudes of travelling waves, a new busbar protection scheme can be constructed, which achieves a high reliability relative to other fault‐travel‐wave‐based algorithms. According to simulation results on a 500 kV substation modelled in ATP‐Draw, the graphical preprocessor to ATP‐EMTP windows version, the proposed algorithm is effective in determining various types of faults. [ABSTRACT FROM AUTHOR]

Fault location estimation in series compensated transmission lines is quite difficult because a non‐linear current dependent circuit appears between the substation and fault point. In particular, the faults which occur at different locations at the same time in different phases known as multi‐location faults has not been addressed by researchers. Other types of fault that may occur in transmission lines are transforming faults where one type of fault transforms to another type fault after some time. In this study, a fault location estimation scheme using artificial neural network (ANN) is presented for multi‐location faults, transforming faults as well as for commonly occurring shunt faults in thyristor controlled series capacitor (TCSC) compensated transmission line. DB‐4 wavelet is used for pre‐processing of the three‐phase current and voltage signals. The shunt capacitance of the line is considered based on distributed parameter line model. Feasibility of the ANN‐based fault location algorithm is tested under a wide variation of parameters, such as fault type, location, fault resistance and fault inception angle. Fault location errors are within 0.001–1% range. [ABSTRACT FROM AUTHOR]

To ensure reliable operations of power transformers, online condition monitoring needs to be performed. However, extensive noise can be coupled into measured signals and cause ambiguities in evaluating transformers' conditions. This study proposes a hybrid method, which combines pre‐whitening and blind equalisation for de‐noising the signals obtained from online partial discharge (PD) measurements of transformers. A measured signal is first gone through a pre‐whitening process for initial noise reduction and then processed by blind equalisation. Finally, an equalised signal that can reveal PD source in a transformer is converted to a kurtogram for an accurate PD pattern representation. The proposed method has been applied to signals obtained from laboratory experiments and online measurements of transformers at substations. Results show that the method can effectively de‐noise PD signals contaminated by severe noise and consistently represent PD patterns induced by different PD sources. [ABSTRACT FROM AUTHOR]

To design high‐sensitivity sensors is one of the critical issues to be solved for ultra‐high‐frequency (UHF) partial discharge (PD) detection in substations. Commonly‐used UHF sensors usually use ultra‐wideband antennas for the frequency bands ranging from 300 MHz to 1.5 GHz. To avoid interference in the frequency bands, such as signals generated from mobile phones, a new multi‐band UHF sensor is proposed based on the loop antenna theory and meandering technique, which reduces the sensor size, provides high sensitivity and exhibits omnidirectional performance. The sensor works in the bandwidth ranges of 480–520, 800–850 and 1100–1200 MHz, and has sensitivity of more than 10 mm. The PD detection platform was set up, three typical insulation defects, such as corona discharge, surface discharge and free metal particle discharge, were designed, and then the tests were performed to compare the performance of the multi‐band sensor and broadband sensor. The results show that the multi‐band sensor's bandwidth covers the main spectra of PD signals, thereby can be used for detecting most kinds of PD signals. The sensor's sensitivity is higher than that of the broadband sensor with its size occupying only 5% of the latter, meeting the requirements for detection of PD sources in substations. [ABSTRACT FROM AUTHOR]

A new procedure focused on reliability analysis of subtransmission systems supported by the state enumeration technique is presented. This new methodology is conducted in three stages. First, a classical state enumeration reliability assessment is performed for the branch‐node model of a subtransmission system, assuming that substations are perfectly reliable. Second, a detailed model of the subtransmission system is considered and the reliability of each substation is assessed by considering them in a 'one‐by‐one' process, supposing perfect operation for the branch‐node model. Finally, the reliability indices calculated in the first and second stages are analytically combined to obtain the reliability indices for the subtransmission system (system reliability indices) and for the load nodes of the distribution system (load‐node reliability indices). Test results show that the proposed methodology is suitable for both planning studies and 24 h‐ahead security assessment. [ABSTRACT FROM AUTHOR]

This study proposes a novel approach for load modelling fulfilled in Guangdong Power Grid, Southern China. Dynamic load modelling lies on real‐time data provided by load disturbances. These data can be acquired by power quality equipment fixed on each substation. This study introduces the approach to data processing and load modelling during asymmetric disturbance to solve the problems of insufficient inartificial disturbance data. In order to improve the global optimisation capability and identification efficiency in multi‐dimensional function, an improved clone selection algorithm is proposed, which includes adaptive‐adjust Gaussian mutation operators and the directional evolution mechanism, and also using the character of parameters independence between induction motor model and ZIP model referring to the third‐order induction‐motor paralleling ZIP model in BPA. The results of practical load modelling prove that the proposed algorithm has great effects on improving model precision and adaptability. Finally, the influences on power angle, frequency, voltage and power between dynamic load model and ZIP are discussed. [ABSTRACT FROM AUTHOR]

Erdbebenerschütterungen können in sandigen im Grundwasser stehenden Gründungsböden zur Bodenverflüssigung mit einem erheblichen Porenwasserdruckaufbau führen. Dies ist weitläufig als Liquefaction bekannt. Durch den Aufbau des Porenwasserdruckes können die wirksamen Korn-zu-Korn-Spannungen maßgeblich abgebaut und dadurch die Scherfestigkeiten im Untergrund vermindert werden. Im ungünstigsten Fall kann dies bis zum Grundbruchversagen der gesamten Bauwerksgründung führen, oder der Porenwasserdruck kann je nach Gründungstiefe und Sohlpressung die in den Untergrund eingebetteten Baukörper aufschwimmen lassen. Nachfolgend wird vom Bau einer 400-kV- Hochspannungsanlage zur Stromversorgung des stark von Erdbeben beanspruchten Südwestens am Kaspischen Meer berichtet und vom geotechnischen Entwurf der dort flach gegründet ausgeführten Einzelfundamente, die für den Lastfall der Bodenverflüssigung beim Bemessungerdbeben auszulegen waren. Shallow foundation of a 400-kV-substation at the Caspian Sea with shear failure analysis at liquefaction Earthquakes in case of high ground water tables in sandy foundation soils could lead to liquefaction with remarkable pore water pressure. By this pore water pressure the effective grain-to-grain-stresses and thus the shear strength of the subsoil could be reduced significantly. As a worst case scenario this may result in a shear failure of the entire building foundation, or depending on the foundation depth and pressure the foundation structures due to the pore water pressure may be damaged by uplift. Subsequently it will be reported about the construction of a 400 kV substation for the power supply in the southwest of the Caspian Sea. For this area heavily exposed by earthquakes the geotechnical conceptual design for the foundation with shallow single footings will be highlighted, which had to be designed for the load case of liquefaction due to the design earthquake. [ABSTRACT FROM AUTHOR]

Everyday experience and scientific observations, including those made as far back as the 18th century, indicate that lightning most often strikes individual structures elevated above the earth, these may high voltage substations. The lightning conductors as a means of protection from direct lightning strokes were used much before the beginning of the present era, but they acquired wide recognition only in the middle of 18th century as a result of the work of Benjamin Franklin. The paper presents an approach to teaching high voltage course using specially designed exercises that can be done using MATLAB. This paper present MATLAB based software to design substation lightning protection. Evaluation of the simulation with 40 students is very positive in terms of their developing confidence in and understanding of this simulation. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 19: 256-267, 2011 [ABSTRACT FROM AUTHOR]

A unique method of predicting lightning outage rates for substations, taking into account statistics-based lightning characteristics, has been developed. The proposed method features the application of a combination of two processes: a high-accuracy lightning surge analysis applying the electromagnetic transient program (EMTP) and a statistical data analysis using a general-purpose spreadsheet software. By employing an original tool applying the proposed prediction method, which is installed in a personal computer, an optimal lightning protection for substations can be designed. In this paper, several analysis models are proposed for lightning characteristics including lightning surge. The validity of the proposed method was confirmed by comparing the transmission line outage rates derived by the models with the outage data gained during actual observations. It was found that the predicted lightning outage rates for 500-kV substations were relatively low, and this finding revealed that it is possible to decrease the impulse withstand voltage level (LIWV). © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 64–75, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10300 [ABSTRACT FROM AUTHOR]

A technique for the fast identification of partial discharge (PD) sources is proposed for the detection of mechanical failure or damage to insulation materials by using wireless remote control and monitoring systems in substations. An estimation of the number of PD sources can help to evaluate the insulation performance and lifetime of power equipment. Multiple PD sources can be generated during the operating voltage where their electromagnetic radiations are highly impulsive, non‐Gaussian noise and the resulting probability distribution function is heavy‐tailed. Multiple PD sources can be estimated by their electromagnetic radiations via blind source separation (BSS) and measuring the excess kurtosis using low‐cost wireless intelligent electronic devices. The efficiency and performance of the proposed method is demonstrated by simulating PD sources based on the spatial Poisson point process where the number of sources is a random variable not known by the receiver. Assuming non‐white and decorrelated or non‐Gaussian and independent sources, results show that the number of significant PD sources can be estimated with low error rate. Underdetermined problems in BSS can affect performances. [ABSTRACT FROM AUTHOR]

In the simulation of electromagnetic fields produced by a point source located in multilayer media, the conventional image method requires an infinite number of images, while the method of complex images only needs a few ones to get an accurate solution. Based on the method of complex images, an approach for simulating grounding systems in multilayer soils is introduced in this paper, and the corresponding Green functions are derived. Software for simulating grounding systems in up to six-layer soils has been developed, and the grounding systems with any complicated structure can be located anywhere in multilayer earth models. Copyright © 1999 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In recent years, transmission line arresters have been installed to protect overhead power transmission lines from backflashovers caused by lightning. In addition, it has been expected that substation lightning surges incoming via transmission lines can be suppressed by them. However, the suppression effect by those with series gaps has not been investigated sufficiently. The author has measured lightning surges at two 77-kV substations from 1990 to 1993. As the transmission line arresters have been mounted on the towers since 1992, the lightning surges due to the sparkover of the series gap of the transmission line arresters can be observed at the substations. In this paper, the lightning surge waveforms due to such sparkover have been analyzed in detail. Next, an accurate EMTP simulation method considering the induced lightning surge voltages has been proposed. Finally, their suppression effect has been investigated by simulation corresponding to each mounting method. © 1999 Scripta Technica, Electr Eng Jpn, 126(4): 30–39, 1999 [ABSTRACT FROM AUTHOR]

In order to improve power supply reliability, it is necessary to prevent lightning faults in transmission lines and substation apparatus. However, faults are caused occasionally in lower-voltage power systems, particularly at the 77 kV level. The governing factor for insulation strength of substation apparatus is the lightning impulse voltage, and it is necessary to know the voltage level and distribution in a substation caused by lightning surges in order to investigate rational insulation coordination. For this purpose, the authors measured lightning surges at two 77 kV conventional substations from 1990 to 1993. In this paper, the characteristics of induced lightning surges and back flashover lightning surges are described. Comparisons of related surge voltages at two substations, the power line phases in grounding faults, and the equivalent capacitance of the substations are also discussed. © 1998 Scripta Technica, Electr Eng Jpn, 124(3): 40–48, 1998 [ABSTRACT FROM AUTHOR]

An indoor distribution substration simulation system based on virtual reality technology has been developed. The system is designed to give the user the feeling of actually touring a substation for routine inspection. Various states of the substation facilities, such as the opening and closing of the doors and the disconnectors as well as the relocation and extension of the installations, can be simulated. In the event the user approaches the energized components of the equipment and fails to keep the specialized insulation distance from them, the system first sounds an alarm, and then a flashing red light on the display warns of passage beyond the safety point and that the operation has suffered an electric shock. Validation of equipment operating procedures, training of unskilled workers and work-schedule preparation can be upgraded by using this system. [ABSTRACT FROM AUTHOR]