Grounding Network Research Articles

Topological Image Reconstruction of Regular Grounding Network Based on Hough Transform

Topological Image Reconstruction of Regular Grounding Network Based on Hough Transform

A faulty feeder selection method for SLG faults based on active injection approach in non-effectively grounded DC distribution networks

Identifying single-line-to-ground faults in non-effectively grounded DC distribution networks is challenging because the fault current is fleeting in the transient stage and negligible in the fault steady stage. First, an active signal injection method is proposed to inject signals into the DC network after the fault occurs. And the fault characteristics of the zero-mode fault circuit including the injected signal are analyzed. Second, a zero-mode parameter identification algorithm is proposed to calculate the length of each feeder based on the injected signal in the fault steady stage. It is found that the calculated length of the healthy feeder corresponds to its actual length, but the calculated result of the faulty feeder is the opposite of the total length of all healthy feeders. Finally, a faulty feeder selection method based on the polarity of the calculated length is proposed. The simulation results shown that the method can select faulty feeders under conditions of up to 5000 Ω transient resistance and 20 dB noise.

Gaze-assisted visual grounding via knowledge distillation for referred object grasping with under-specified object referring

Understanding human referring intention is the key challenge in referred object grasping tasks. Current Referring Expression Comprehension (REC) and Referring Expression Segmentation (RES) methods enable robots to ground the referred object through precise language commands while ignoring the under-specified referring expressions in practical scenarios. In this paper, we propose a gaze-assisted visual grounding network, which efficiently estimates the human gaze via knowledge distillation techniques to provide visual guidance for inferring human referring intention. Specifically, a gaze auxiliary network is introduced to incorporate the human gaze to implicitly eliminate the referring ambiguity. A cross-attention-based multi-modal fusion module is designed with a balanced structure to project the diverse modalities into a common feature space to balance the inter-modal information. A tabletop object dataset with human gaze and under-specified referring expressions was established to evaluate our method. Experimental results show that our method achieves advanced results compared to the state-of-the-art visual grounding method, with a gain of 8.23% on REC precision and 10.44% on RES mIoU (mean Intersection over Union). The effectiveness and superiority of our method are also demonstrated through real-world referred object grasping experiments. The code is now available at https://github.com/robotseu/GVGNet_KD.

Research on the countermeasures of the single-phase-to-earth faults in flexibly grounded distribution networks

In a neutral, flexible, grounded distribution network, the phenomenon that a single-phase ground fault with high impedance connected in parallel with a low resistance can result in a relatively lower zero-sequence current flowing through the faulty feeder. This zero-sequence current can make it a challenge to use zero-sequence protection schemes to accurately identify and effectively protect the faulty feeder. In terms of the aforementioned challenge, based on the zero-sequence equivalent circuit of a single-phase-to-earth fault, this paper conducts an investigation on the phase difference between the zero-sequence current and the non-fault phase line voltage at power frequency in flexible grounding distribution network with different grounded conditions, both before and after the introduction of a parallel low-resistor connection. Subsequently, a criterion for selecting the faulty feeder is developed based on the observed phase difference characteristics following the implementation of the parallel low-resistor connection. Furthermore, a disposal strategy for single-phase-to-earth faults is formulated, which takes fault resistance estimation into account. To validate the proposed method, a simulation model of a flexible grounding distribution network is implemented with PSCAD/EMTDC. The effectiveness and reliability of this method in multiple scenes, including the initial fault conditions, sampling frequency, and distributed generation (DG), are proved through simulation results.

Earth Fault Location for Non-Directly Grounded Distribution Networks

Earth Fault Location for Non-Directly Grounded Distribution Networks

Train-earth-grid coupling DC magnetic bias model for stray current diffusion

The DC magnetic bias phenomenon in transformers can result in increased noise and harmonic components. This study focuses on the DC magnetic bias generated by stray currents in the DC traction power supply system of neutral grounding transformers under multiple train operation conditions. A two-layer soil model is utilized to calculate geodetic potential, with rail potentials from both mainline and depot serving as sources for stray current within the model. Two paths of stray current intrusion into the transformer via the grounding network and cable armor layer from the Main substation have been modeled and analyzed. A simulation test has been designed to verify that the maximum error between experimental data and model calculation data is 8.87%. The implementation of a blocking connection device between the depot and mainline, as well as a change in grounding strategy for the metal protective layer, can effectively reduce DC bias magnetic current in the substation.

Comprehensive Visual Grounding for Video Description

The grounding accuracy of existing video captioners is still behind the expectation. The majority of existing methods perform grounded video captioning on sparse entity annotations, whereas the captioning accuracy often suffers from degenerated object appearances on the annotated area such as motion blur and video defocus. Moreover, these methods seldom consider the complex interactions among entities. In this paper, we propose a comprehensive visual grounding network to improve video captioning, by explicitly linking the entities and actions to the visual clues across the video frames. Specifically, the network consists of spatial-temporal entity grounding and action grounding. The proposed entity grounding encourages the attention mechanism to focus on informative spatial areas across video frames, albeit the entity is annotated in only one frame of a video. The action grounding dynamically associates the verbs to related subjects and the corresponding context, which keeps fine-grained spatial and temporal details for action prediction. Both entity grounding and action grounding are formulated as a unified task guided by a soft grounding supervision, which brings architecture simplification and improves training efficiency as well. We conduct extensive experiments on two challenging datasets, and demonstrate significant performance improvements of +2.3 CIDEr on ActivityNet-Entities and +2.2 CIDEr on MSR-VTT compared to state-of-the-arts.

Word2Pix: Word to Pixel Cross-Attention Transformer in Visual Grounding.

Current one-stage methods for visual grounding encode the language query as one holistic sentence embedding before fusion with visual features for target localization. Such a formulation provides insufficient ability to model query at the word level, and therefore is prone to neglect words that may not be the most important ones for a sentence but are critical for the referred object. In this article, we propose Word2Pix: a one-stage visual grounding network based on the encoder-decoder transformer architecture that enables learning for textual to visual feature correspondence via word to pixel attention. Each word from the query sentence is given an equal opportunity when attending to visual pixels through multiple stacks of transformer decoder layers. In this way, the decoder can learn to model the language query and fuse language with the visual features for target prediction simultaneously. We conduct the experiments on RefCOCO, RefCOCO+, and RefCOCOg datasets, and the proposed Word2Pix outperforms the existing one-stage methods by a notable margin. The results obtained also show that Word2Pix surpasses the two-stage visual grounding models, while at the same time keeping the merits of the one-stage paradigm, namely, end-to-end training and fast inference speed. Code is available at https://github.com/azurerain7/Word2Pix.

Location method of high-impedance fault based on transient zero-sequence factor in non-effectively grounded distribution network

Location method of high-impedance fault based on transient zero-sequence factor in non-effectively grounded distribution network

A Regionally Indicated Visual Grounding Network for Remote Sensing Images

A Regionally Indicated Visual Grounding Network for Remote Sensing Images

Knowledge enhanced bottom-up affordance grounding for robotic interaction.

With the rapid advancement of robotics technology, an increasing number of researchers are exploring the use of natural language as a communication channel between humans and robots. In scenarios where language conditioned manipulation grounding, prevailing methods rely heavily on supervised multimodal deep learning. In this paradigm, robots assimilate knowledge from both language instructions and visual input. However, these approaches lack external knowledge for comprehending natural language instructions and are hindered by the substantial demand for a large amount of paired data, where vision and language are usually linked through manual annotation for the creation of realistic datasets. To address the above problems, we propose the knowledge enhanced bottom-up affordance grounding network (KBAG-Net), which enhances natural language understanding through external knowledge, improving accuracy in object grasping affordance segmentation. In addition, we introduce a semi-automatic data generation method aimed at facilitating the quick establishment of the language following manipulation grounding dataset. The experimental results on two standard dataset demonstrate that our method outperforms existing methods with the external knowledge. Specifically, our method outperforms the two-stage method by 12.98% and 1.22% of mIoU on the two dataset, respectively. For broader community engagement, we will make the semi-automatic data construction method publicly available at https://github.com/wmqu/Automated-Dataset-Construction4LGM.

Faulty feeder selection based on improved Hough transform in resonant grounded distribution networks

Due to the weak fault characteristics and inaccurate fault line selection during high impedance faults, this paper proposes a new method for fault line selection in resonant grounded distribution networks based on improved Hough transform. Firstly, the variational modal decomposition (VMD) algorithm decomposes each feeder's zero sequence power under different operating conditions, then, using Sample entropy and Pearson correlation coefficient, selects the intrinsic mode function (IMF) with the highest correlation strength with the zero-sequence power of each feeder, called IMFK. Secondly, using the Hough transform to detect IMFK, obtaining the fitted straight line and IMFK angle during the fault's initial stage. The problem of identifying the zero-sequence power mode trend is transformed into a mathematical problem of determining the geometric shapes of straight lines and curves in the zero-sequence power mode image. Finally, a line selection criterion is established by integrating correlation coefficients to identify the faulty feeder in the distribution network system when a single-phase grounding fault occurs. The PSCAD simulation and on-site measurement results show that the proposed method can ensure the effectiveness and adaptability of the line selection.

УДОСКОНАЛЕННЯ ТА ОПТИМІЗАЦІЯ СИСТЕМ ЗАЗЕМЛЕННЯ ПІДСТАНЦІЙ ВИСОКОЇ НАПРУГИ

The article conducted research aimed at studying the modern challenges and prospects of improvement and optimization of grounding systems at high voltage substations. High -voltage power systems require high attention to safety and reliability, especially when designing, equipping and operating grounding systems. This is critical for protecting people and equipment from electrical shocks and overvoltages, as well as reducing the risk of accidents. The development of grounding systems is closely related to the technologies of production and transmission of electricity, with requirements for protection against atmospheric discharges, transitional processes and ensuring electromagnetic compatibility. Modern grounding systems should take into account not only safety and reliability, but also environmental standards, efficiency of resource use and integration into different energy systems. This requires the use of new materials, design, maintenance and innovative technologies. The design of an effective grounding system should take into account various factors: type of equipment, geological conditions, climatic features, electromagnetic interference. The choice of materials for grounding depends on their electrical characteristics, durability and corrosion resistance. Scientific studies in the field of grounding systems include modeling current and the impact of pulse currents, analysis of transitional behavior in grounding networks, development of parametric databases for design, influence of the state of contact on grounding behavior in transitional processes, as well as investigation.The purpose of the work was to search for factors that influence the operation of grounding systems during impulse transitional processes to optimize these systems. The use of theoretical research, the analysis of regulatory bases and the use of software complexes made it possible to visualize the picture of the voltage distribution in impulse transitional processes. Such studies emphasize the importance of ensuring pulsed grounding stability, which depends not only on geometry, but also on the electromagnetic properties of the soil. Under the effect of high pulse currents, grounding systems require accurate design for effective "discharge" of pulse currents and ensuring the proper level of electromagnetic compatibility at substations.

Implementation and laboratory verification of method utilizing phase and neutral quantities for detection and location of low‐current earth faults in resonant grounded networks

AbstractEarth faults is a challenging fault type to locate in resonant grounded networks due to their naturally low fault current, and the problem increases with an increased fault impedance. This paper describes the detailed implementation and laboratory testing of a method for detection, location and clearing of earth faults with very small fault currents. The method consists of two indicators used in the fault detection stage, where their simultaneous operation ensures selective fault detection and faulty feeder selection. One of these indicators also enables continuous fault indication throughout a sectionalizing process. The laboratory tests demonstrate that both indicators function as intended, and it is the current sensors which ultimately limit the attainable sensitivity. Faults up to 15 kΩ were detected successfully in the laboratory network based on phase current measurements, while the sectionalizing indicator showed much higher sensitivity and functioned as intended in a 50 kΩ fault. Measurements from one field test in a 22 kV network corroborate the laboratory results and demonstrate the expected earth fault indicator response.

Multi-target fault ride-through strategy for transformerless MMCs under asymmetric grounding faults in AC/DC hybrid distribution networks

In AC/DC hybrid distribution networks (HDNs), when asymmetric grounding faults occur, transformerless multiterminal modular multilevel converters (MMCs) should achieve three key targets of fault ride-through (FRT): 1) limiting the unbalanced fault currents; 2) injecting currents to support grid voltages in case of disconnection from grids; and 3) eliminating the zero-sequence circulating currents (ZSCCs) from fault networks through MMCs to nonfaulted networks. However, in medium voltage-level HDNs, the line impedances are mainly resistive-inductive, and traditional current injection methods are no longer effective. Moreover, in neutral nondirect grounding networks with multiple AC voltage levels, the voltages of nonfaulted phases rise, and it is difficult for MMCs to achieve fault current control. To solve the above issues, this manuscript proposes a multi-target FRT strategy. First, negative-sequence current controllers are used to eliminate the negative-sequence fault currents. Then, to support the positive-sequence voltages of grids, optimal and suboptimal active-reactive current references based on the line impedance ratios are proposed. To help transformerless MMCs with low modulation indices eliminate zero-sequence circulating currents, two zero-sequence voltage compensation modes and an improved zero-sequence current eliminator are proposed. Finally, the proposed fault current control is verified in MATLAB/Simulink.

Protection method of traction power supply system for low and medium speed Maglev traffic based on fault traveling wave features

AbstractLow and medium speed magnetic levitation traffic with short power supply distance and complex grounding network structure, prone to power supply rail grounding faults. However, the existing fault location methods do not accurately locate the fault point, making it difficult for the protective device to act to cut off the fault. To address the above problems, this paper builds a dynamic simulation model of the low and medium speed magnetic levitation power supply rails to study the distribution characteristics of the fault traveling waves after a ground fault occurs in the power supply rails, and analyses the generation mechanism of the traveling wave spectrum through formula calculation. First, the difference in current between the positive and negative bus bars is analyzed to determine whether a ground fault has occurred. Second, the direction of the current difference between stations is compared to locate the faulty section. Finally, the fault distance is calculated from the frequency difference of the fault voltage at the double‐ended station. Through simulation, the method is validated to be unaffected by fault location, fault transition resistance, noise interference, and is applicable to short circuit faults caused by lightning strikes, and the ranging error always remains within 20 m. The method has strong robustness, can effectively solve the problem of protection misoperation and accurately locate the fault point. It is suitable for low and medium speed magnetic levitation transportation power supply rail ground fault.

A new method for single‐phase high resistance grounding fault protection in low resistance grounded distribution networks

AbstractThe neutral point of the distribution network is grounded with low resistance, which can quickly remove single‐phase grounding fault and effectively suppress overvoltage. However, the existing zero‐sequence overcurrent protection has a high setting value. In the case of large fault resistance and weak fault current, the existing protection methods may refuse to operate. Based on the waveform characteristics of the zero‐sequence current of each outgoing line in the distribution network, this article proposes a new method for single‐phase high resistance grounding fault protection in low resistance grounded distribution network, which combines cosine distance and improved K‐means algorithm. First, the cosine distance between zero‐sequence current of every two outgoing lines is obtained, and the cosine distance matrix used to describe the fault characteristics is constructed. Then the improved K‐means algorithm is used to cluster the row vectors of the cosine distance matrix to obtain the convergent cluster center and cluster label, so that the fault line can be determined. This protection method does not need to set the threshold value manually, and has strong ability to handle large fault resistance. It can effectively deal with noise interference and intermittent arc grounding fault, and still has good adaptability in scenarios such as change of fault initial phase angle, change of fault location, access of distributed generations and occurrence of two outgoing lines in phase to grounding fault. Finally, a model is built, and the effectiveness of the proposed method is proved by the simulation of grounding fault.

Estimating distance to transient and restriking earth faults in high-impedance grounded, ring-operated distribution networks using current ratios

Earth faults occur frequently in distribution networks, and in resonant grounded networks they are challenging to locate precisely due to their naturally low fault current. Transient and restriking faults are more challenging still due to the short time available for the fault location logic, as well as the absence of steady-state conditions. This paper investigates the performance of three fault location methods utilizing the ratios of various current components in a network operated in a closed-ring configuration. A frequency dependent model of a distribution network is used to simulate transient and restriking faults, and both isolated grounding and resonance grounding are considered. The results show that fault location based on negative-sequence currents is able to locate transient faults, and its accuracy of a few hundred metres is comparable to what has been observed during permanent faults. A zero-sequence method is observed to be less accurate, particularly in resonant grounded networks. A transient method is also proposed, and while it is fast, it is ultimately limited by the presence of loads and branches in the network. It is concluded that the negative sequence method is best suited for transient and restriking faults.

Simulation and Experimentation of a Grounding Network Detection Scheme Based on a Low-Frequency Electromagnetic Method.

The grounding network is a significant component of substations, and the corrosion of its ground resistance is predominantly detected using the electromagnetic method. However, the application of electromagnetic methods for detecting corrosion within earthing networks has received relatively limited attention in research. Currently, the prevailing method utilizes electromagnetic techniques to identify the breakage points within the given earthing network. In this study, we propose a corrosion detection method for grounding networks based on the low-frequency electromagnetic method, which measures the resistance value between individual nodes of the network. Specifically, an excitation source signal of a predetermined frequency was transmitted to the measurement segment of the grounding network, which facilitated the direct measurement of the strength of the induced magnetic field above the center of the measuring conductor. The recorded electromagnetic data were subsequently uploaded to the host computer for data processing, and the computer interface was constructed based on a LABVIEW design. By leveraging the relationship between the induced electric potential, current strength, excitation source strength, and additional voltage detection devices, the resistance of the conductor under examination could be determined. Furthermore, the proposed method was tested under suitable conditions, and it demonstrated favorable results. Thus, the proposed method can serve as a foundation for developing electromagnetic testing instruments tailored to the investigated grounding network.

A New Method for Fault Detection and Location in a Low-Resistance Grounded Power Distribution Network Using Voltage Phasor of D-PMUs Data

A New Method for Fault Detection and Location in a Low-Resistance Grounded Power Distribution Network Using Voltage Phasor of D-PMUs Data