Sag Method Research Articles

Rapid visual detection method of highway pavement sag based on improved Yolov7-tiny

Different weather and light conditions will affect the detection of pavement sag. And the camera field of view is limited, can not fully cover the entire highway road surface, resulting in higher difficulty in road sag detection. Therefore, a rapid visual detection method for highway pavement sag based on improved Yolov7-tiny is proposed. The structure elements are determined, and the small noise points in the image are removed by etching operation, and the morphology of the highway surface is completed. Input the processed highway pavement sag image into YOLOv7-tiny network, improve the input module and backbone network, and output the irregular shape of the sag image target. Fuzzy C-Means (FCM) clustering algorithm is introduced and objective function is established to realize the morphological feature visual detection of highway pavement depression. The experimental results show that: The method has smaller entropy, larger fuzzy coefficient, higher peak signal-to-noise ratio, and clearer features of pavement depression images.

A novel cause identification method of voltage sag for auxiliary power quality monitoring

A novel cause identification method of voltage sag for auxiliary power quality monitoring

A comprehensive evaluation method of DC voltage sag in medium–low voltage DC distribution system

The development of the DC distribution system (DCDS) has attracted increasing attention, due to its technological superiorities in integrating new energy sources and DC power loads more friendly and effectively. In this paper, a comprehensive evaluation method is proposed for the medium–low​ voltage DCDS to handle the voltage sag assessment problem. Firstly, the topology structure and control strategy of the DCDS are stated, and the pragmatic characteristics of DC voltage sag on the medium-voltage and low-voltage sides based on the dual active bridge (DAB) converter are analyzed. Then, considering the difference in the evaluation indexes of the low-voltage and medium-voltage sides of the DCDS, a comprehensive evaluation system is established. Further, the analytic hierarchy process (AHP) and criteria importance through intercriteria correlation (CRITIC) weighting method are applied to achieve comprehensive weighting, and the TOPSIS model is used to describe the severity of DC voltage sag. Using MATLAB, a 10 kV/ 750 V DCDS with the DAB is built, and comparative assessments are performed. The results show that the proposed method can reasonably evaluate the DC voltage sag of the low-voltage and medium-voltage sides. Compared to the evaluation schemes based on the single index, the proposed method can more effectively reflect the waveform features of the DC voltage sag, and it is very appropriate for the voltage dip evaluation of the medium–low voltage DCDS.

Study on the sag of ultra high voltage conductor with large-tonnage tension insulator string

The aim of this paper is to establish a unified state equation of overhead line mechanics. An accurate calculation method of non-uniform load sag is proposed based on the simply supported beam theory. It is suitable for isolated span and continuous span. Meanwhile, this paper investigates the law and error influence of sag in both isolated pan and continuous span considering some sensitive factors, such as tensile force, span length, number of spans, elevation difference angle, length and weight of tension insulator string. The efficacy of the recommended algorithm for conductor sag with large-tonnage tension insulator string line is validated in the end.

Feature Analysis Method of Voltage Sag based on Sag Slope

At present, most of the analysis of the amplitude and duration of the voltage sag is based on the probability distribution map of a large number of measured data, in order to solve this problem, a calculation method is proposed to transform the sag amplitude and duration into the sag slope and sag amplitude time, which can quantitatively express the tilt degree of the voltage sag waveform and the persistence at the lowest amplitude. After analyzing the simulation waveforms of short circuit fault and transformer excitation by slope calculation method, the values of sag slope and sag amplitude time obtained are more perfect than the original sag amplitude and duration description, which is beneficial to the follow-up study of voltage sag.

Sag and temperature estimation method based on improved machine learning for transmission line

Sag and temperature estimation method based on improved machine learning for transmission line

Overhead Transmission Lines Sag and Voltage Monitoring Method Based on Electrostatic Inverse Calculation

Transmission line sag and voltage are key information to reflect the real-time operation state of power grid. Contactless measurement method has great advantages of no electrical contact, flexibility and mobility, but it is also vulnerable to environmental changes. In this article, a novel overhead transmission line contactless sag and voltage monitoring method is proposed, which only needs a simple potential measurement array and can apply to dynamic conductor measurement. The electrostatic coupling model between the transmission lines and the measuring points is established. The sag and voltage inversion calculation model is proposed and the ill-posed problem is solved. The measurement array and the data acquisition method are designed. The equivalent measurement area (EMA) is determined considering the difference between 3-D model and 2-D model of overhead line. Finally, the effectiveness of the proposed method is verified by single-circuit transmission line simulation and scale-down experiment.

Evaluation of nonylphenol surfactant in enhanced oil recovery by SAG and WAG method

The oil production from reservoirs using foams stabilized by surfactants is currently a promising technique to increase sweep efficiency. However, choosing the ideal surfactant and how it will be applied within the production technique is essential for an expressive oil recovery yield, thus requiring careful studies and tests in order to have a good application performance. In this work, the authors aimed to evaluate the use of a nonionic surfactant with a high degree of ethoxylation (nonylphenol 100EO) to generate divergent foams in the SAG method (surfactant alternating gas injection) in order to compare it with the WAG method (water alternating gas injection process) under the same injection conditions. The experiments showed that the SAG method increased the oil production up to 31.37%, while the WAG increased it up to 27.70%. It was possible to verify through the tests that the SAG containing nonylphenol 100EO exhibited greater efficiency ithin a smaller number of injection cycles (from 26.71% up to 31.37%), while the WAG presented the opposite behavior, which efficiency decreased with the smaller number of injection cycles (from 25.64% to 10.96%).

A Comprehensive Weight-Based Severity Evaluation Method of Voltage Sag in Distribution Networks

With the increasing use of sensitive loads in frequency converters and in relays in distribution networks, voltage sag has become a major power quality issue that urgently needs to be solved. For the purpose of improving the understanding of voltage sag severity in distribution networks, a comprehensive weight-based severity evaluation method of voltage sag is presented in this paper. First, a multi-side index system that takes into account the combined influence of the source, network, and the load is established. A comprehensive weight method, which combines the improved analytic hierarchy process (IAHP) and the entropy method, is then adopted to determine the index weight. The weight of each index and the degree of superiority are linearly weighted to obtain the severity of voltage sag at different observation points. Finally, the effectiveness of the proposed method is verified using a distribution network model established in DIgSILENT PowerFactory (15.1.7, Gomaringen, Germany).

Investigation of sag behaviour for aluminium conductor steel reinforced considering tensile stress distribution.

Sag calculation plays an important role in overhead line design. Since the tensile stress of aluminium conductor steel reinforced (ACSR) is required for the sag calculation, an analysis on sag behaviour when considering the tensile stress distribution can be very useful to improve the accuracy of sag results. First, this paper analyses the ACSR tensile stress distribution arising from the temperature maldistribution through proposing a new calculation formula. A finite-element analysis (FEA) model of ACSR is conducted for the solution of the new formula. By using the results, the error and limitations of the existing sag calculation methods for ACSR are discussed. As the critical point of sag calculation, knee-point temperature is solved iteratively involving the tensile stress maldistribution phenomenon in aluminium wires. Based on this iterative solution, an improved analytical method for the ACSR sag calculation considering the creep effect is presented and also compared with the hybrid sag method. The results show that these two methods are basically coincident without the consideration of creep effect, while there are non-negligible differences between them as the creep strain is involved. Compared with the existing analytical methods, the improved sag calculation method proposed in this paper can be applied in more extensive situations.

Numerical Study of Immiscible Foam Propagation in Porous Media in the Presence of Oil Using an Implicit-Texture Foam Model

Gas injection is one of the established methods in enhanced oil recovery. Nevertheless, poor sweep efficiency and viscous instabilities result in early gas breakthrough. Lowering injected gas mobility through foaming is a potential solution to solve the forenamed challenges. Although foaming of the injected gas has been proposed in various stages of oil production, comparatively few studies are carried out about foam injection modeling in the presence of oil. In this study, we aimed to numerically investigate the immiscible foam propagation in a thick, heterogeneous, water-flooded sandstone reservoir with a primary goal to control the surge of the produced gas–oil ratio (GOR) and also the possible incremental oil production by foam. To this end, the implicit-texture local-equilibrium foam model was used to address that how a stable foam front could affect fluid saturation and their mobility in the presence of waterflood residual oil. We treated the reservoir model by considering a pair of horizontal injection/production well through the upper and lower parts of the reservoir to mimic the foam-assisted gravity drainage scheme. Foam generation was considered through alternating (SAG) and simultaneous injection of gas and surfactant solution, and its performance was compared with continuous gas injection and water alternating gas injection. Results showed that gas-phase mobility was reduced in the presence of foam, leading to delaying of gas breakthrough and thereby improvement of gas sweep efficiency. The latter caused a significant reduction in produced gas–oil ratio, enhanced the control of the front movement, and resulted in better oil sweeping. In comparison to the SAG method, occurrence of fingering phenomena in foam co-injection was less likely. In addition, foam front in co-injection method exhibited relatively slower movement compared to the SAG method. Also, with ignoring the prescribed pressure constraint in injection well, the stability and uniformity of the generated foam front decreased, leading to more occurrences of fingering and thus reduction in oil recovery.

Method of Voltage Sag Causes Based on Bidirectional LSTM and Attention Mechanism

The voltage sags’ cause recognition is the basis for formulating governance plans and clarifying liabilities for accidents. For voltage sag cause recognition methods based on physical characteristics, new challenges are presented in terms of accuracy, adaptability and algorithm efficiency. Deep learning is a method based on characterizing and learning data. The efficient mechanism of autonomous feature learning can effectively overcome the problems of information loss and generalization ability based on existing physical property methods. The long short-term memory network (LSTM) has the characteristics of memory and can better learn the data characteristics with time series characteristics. Bidirectional LSTM can consider historical information and future information compared with standard LSTM, and has more processing for time series data. While using the attention mechanism can highlight the key influencing factors in the time series and improve the recognition accuracy of the model. For the transient sag time series data, this paper proposes a multi-layer structure based on bidirectional LSTM and attention mechanism to classification recognition. The experiment uses simulation data and measured data to prove that the model has good recognition ability and good anti-noise performance in the recognition of voltage sag causes, and can be reliably applied in practical engineering.

Recognition method of voltage sag causes based on two‐dimensional transform and deep learning hybrid model

The voltage sags' caused recognition is the basis for formulating governance plans and clarifying liabilities for accidents. The diversification of smart grid equipment, the grid-connected power generation of new energy sources and the regional differentiation of power consumption modes pose new challenges to the traditional methods. In this study, a method based on deep learning hybrid model is proposed. The convolutional neural network is used to flexibly receive the voltage after two-dimensional transformation, so as to automatically obtain the time series and spatial characteristics of the voltage sag signals. The deep belief network is used to replace the fully connected layers in convolutional neural network, thereby enhancing the multi-label classification ability of the model. The parameters obtained by the unsupervised training of the stacked sparse denoising auto-encoder are used to initialise the weight of deep belief network, thereby improving the convergence speed and the anti-noise performance of the model. Iterative training and repeated testing of the network using pre-processed simulation data and actual recorded data verify the high recognition accuracy and strong anti-noise performance of the hybrid model. Compared with the traditional methods, the hybrid model also has good generalisation ability and can be effectively applied in practical engineering.

Recognition method of voltage sag causes based on Bi‐LSTM

In recent years, the power quality problem has become more complicated in power grids because of the extensive usage of power electronics and multisource multitransformation features. The method, based on physical characteristics such as time domain, frequency domain and transform domain, is facing challenges in terms of adaptability, algorithm efficiency and accuracy for the recognition of complex disturbance recognition. The bidirectional long short‐term memory network is an algorithm in deep learning. It is based on data for characterization learning, which can effectively overcome the problem of information loss and generalization ability of physical methods. Moreover, it has the characteristics of memory, which can simultaneously consider historical information and future information and can better learn data features with time series characteristics. Aiming at the transient voltage sag time series data, this paper proposes a recognition method of the voltage sag causes based on the bidirectional long short‐term memory network's extraction eigenvalue, the full‐connection layer's high‐dimensional feature extraction and the Softmax network layer's classification. The experiment uses simulation data and measured data to prove that the model has good recognition ability and good antinoise performance in the recognition of voltage sag causes and can be reliably applied in practical engineering. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Voltage sag problems in large‐scale clustering wind farms

Accompanied by the development of large‐scale wind energy and integration into grid in China, wind farm cascading trip‐off accidents resulting from voltage sag have occurred frequently in the past few years. Before proposing countermeasures, it is necessary to clarify the voltage sag problem of wind farms. First, three voltage sag risk indices are proposed. Second, the simplified equivalent circuit of double fed induction generator (DFIG) for short‐circuit calculation, stochastic model of wind speed and the fault model of buses/lines are presented in this paper. Third, assessment method of voltage sag in wind farm, implemented by Digsilent dynamic programming language (DPL), is proposed to analyze the severity and probability of voltage sag. Finally, a case study of wind farm connected to WSCC nine‐bus benchmark systems is analyzed in detail, and the validity of the proposed approach is confirmed. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

VARIATIONS IN METHADONE PRESCRIBING AND OUTCOMES — A SERVICE EVALUATION IN SHEFFIELD AND CHESTERFIELD

BackgroundMethadone is a synthetic opioid used in refractory pain. There is increased awareness of methadone related adverse events including respiratory depression and QTc prolongation. In our region several methods exist...

New Voltage Sag Frequency Evaluation Method Considering the Satisfaction Degree of Sensitive Customer

To meet power customers’ satisfaction is the essential responsibilities of utilities. Considering the property of customer’s satisfaction degree, an analytical interval assessment method of voltage sag is proposed. The customer satisfaction degree is presented by interval number corresponding to the voltage tolerance for the tested equipment installed at the customer side. Based on the determination function derived from the relationship between the voltage magnitude and the length of fault line in the power system, critical fault positions are determined through analytical iterative algorithm. By the variation of satisfaction degree within a given interval, the interval sag frequency is calculated. Moreover, the quantitative sag frequency is determined by the help of the interval sag frequency. The proposed method is applied to a five-bus system and IEEE 30-bus testing system. The simulation results comparing with existing methods have shown that this method is credible and suitable for the practical engineering application.

선택성장영역 크기에 따른 InGaN/GaN 다중양자우물 청색 MOCVD-발광다이오드 소자의 특성

(Received October 12, 2011)(Revised October 24, 2011)(Accepted November 11, 2011)Abstract In general, the fabrications of the LEDs with mesa structure are performed grown by MOCVD method. In orderto etch and separate each chips, the LEDs are passed the RIE and scribing processes. The RIE process using plasma dryetching occur some problems such as defects, dislocations and the formation of dangling bond in surface result in declineof device characteristic. The SAG method has attracted considerable interest for the growth of high quality GaN epi layeron the sapphire substrate. In this paper, the SAG method was introduced for simplification and fabrication of the highquality epi layer. And we report that the size of selective area do not affect the characteristics of original LED. Thediameter of SAG circle patterns were choose as 2500, 1000, 350, and 200µm. The SAG-LEDs were measured to obtainthe device characteristics using by SEM, EL and I-V. The main emission peaks of 2500, 1000, 350, and 200µm were 485,480, 450, and 445 nm respectively. The chips of 350, 200µm diameter were observed non-uniform surface and resistancewas higher than original LED, however, the chips of 2500, 1000µm diameter had uniform surface and current-voltagecharacteristics were better than small sizes. Therefore, we suggest that the suitable diameter which do not affect thecharacteristic of original LED is more than 1000µm.Key wordsSelective area growth, InGaN/GaN, Multi quantum well, MOCVD, Band-filling effect, Screening effect

Customer Satisfaction Based Evaluation Method of Voltage Sag in the Modern Power System

This paper is based on interval data of power customer satisfaction degree. The evaluation method of voltage sag or dip is an analytical one which is used to consider the satisfaction of not only the utility but also the user side. Determining function is from the length of fault line and the voltage magnitude in the modern transmission and distribution network. The critical failure positions method is getting through analytical algorithm combined with iterative features. The range characteristics of satisfaction degree of customer side and the distribution regularities of the uncertainty region are considered in the paper. Then, the quantitative frequency of voltage sag is determined using the interval sag frequency. A small size network and IEEE 30-bus RTS are chosen to comparing with existing and traditional methods. And this novel method is proved to have much more academic value and practical foreground.

Improved Calculation of Sag for a Conductor Supported at Unequal Heights

The sag of conductors of an overhead line is determined from the horizontal tension at the lowest point of the conductors. In a conductor supported at unequal heights the lowest point is calculated, together with the horizontal tension, from hyperbolic expressions using an iterative procedure. In practice the hyperbolic functions are usually approximated by their first two terms. While the results are close to the actual values some differences may arise because the approximate methods may not converge to the exact values. The Newton Raphson sag method presented in the paper applies the Newton Raphson method to obtain fast convergence to the exact values. It is inherently more accurate than the classical iterative procedure based on approximating the hyperbolic functions; and the convergence criterion may be set as small as required. The method is also applicable to a conductor supported at equal heights.