A Simple and Effective Surface Defect Detection Method of Power Line Insulators for Difficult Small Objects

Insulator defect detection plays a vital role in maintaining the secure operation of power systems.To address the issues of the difficulty of detecting small objects and missing objects due to the small scale,variable scale,and fuzzy edge morphology of insulator defects,we construct an insulator dataset with 1600 samples containing flashovers and breakages.Then a simple and effective surface defect detection method of power line insulators for difficult small objects is proposed.Firstly,a high-resolution featuremap is introduced and a small object prediction layer is added so that the model can detect tiny objects.Secondly,a simplified adaptive spatial feature fusion(SASFF)module is introduced to perform cross-scale spatial fusion to improve adaptability to variable multi-scale features.Finally,we propose an enhanced deformable attention mechanism(EDAM)module.By integrating a gating activation function,the model is further inspired to learn a small number of critical sampling points near reference points.And the module can improve the perception of object morphology.The experimental results indicate that concerning the dataset of flashover and breakage defects,this method improves the performance of YOLOv5,YOLOv7,and YOLOv8.In practical application,it can simply and effectively improve the precision of power line insulator defect detection and reduce missing detection for difficult small objects.

Performance Evaluation for Medium Voltage MIMO-OFDM Power Line Communication System

Power line communication(PLC)provides intelligent electrical functions such as power quality measurement,fault surveys,and remote control of electrical network.Most of research works have been done in low voltage(LV)scenario due to the fast development of in-home PLC.The aim of this paper is to evaluate the link-level performance of a medium voltage(MV)MIMO-OFDM communication system based on transmission link under underground power line channel.The MIMO channel is modeled as a modified multipath model in the presence of impulsive noise and background noise.We first perform a measurement on the practical MV MIMO channel parameters for a section of buried cable of 1 km long in Ganzhou city,Jiangxi province,China.Based on the measured channel,we design the frame structure based on an IEEE standard for broadband over power line networks[1]to support MV MIMO-OFDM transmission.According to designed frame structure,we design an encoder and a decoder for a dual binary tail-biting turbo code and optimize some key decoder parameters for low bit error rate performance.Finally,the link-level performance for both spatial multiplexing and spatial diversity are evaluated.Numeral results show that MV MIMO-OFDM is a promising approach to provide both high data rate and link reliability for PLC.

A FAST BIT-LOADING ALGORITHM FOR HIGH SPEED POWER LINE COMMUNICATIONS

Adaptive bit-loading is a key technology in high speed power line communications with the Orthogonal Frequency Division Multiplexing (OFDM) modulation technology. According to the real situation of the transmitting power spectrum limited in high speed power line communications, this paper explored the adaptive bit loading algorithm to maximize transmission bit number when transmitting power spectral density and bit error rate are not exceed upper limit. With the characteristics of the power line channel, first of all, it obtains the optimal bit loading algorithm, and then provides the improved algorithm to reduce the computational complexity. Based on the analysis and simulation, it offers a non-iterative bit allocation algorithm, and finally the simulation shows that this new algorithm can greatly reduce the computational complexity, and the actual bit allocation results close to optimal.

Propagation characteristics of power line harmonic radiation in the ionosphere

Theoretical model and solutions on power line harmonic radiation （PLHR） propagating in the ground, air, and anisotropic homogeneous ionosphere are presented, The theoretical model is verified by the PLHR events observed by the DEMETER satellite. Some propagation characteristics of PLHR based on the model are obtained. This paper is bene- ficial to quantitatively interpret the formation mechanism of PLHR phenomenon.

Avian-power line interactions in the Gobi Desert of Mongolia:are mitigation actions effective?

Background:Electrocution and collisions on power lines are among the leading causes of non-natural mortality for birds.Power lines are exponentially increasing,particularly in developing countries,but mitigation strategies to prevent bird mortality are questionable.Mongolia combines a recently increased power line network,an abundant raptor population,a dangerous crossarm configuration and a habitat with no natural perches,producing many bird-power line interactions.Our aim is to assess the bird mortality caused by power lines in the Gobi Desert of Mongolia,to determine the factors increasing the risk of bird electrocution,and to evaluate the effectiveness of used retrofitting measures.Methods:In July 2019 we covered 132.9 km of 15 kV power lines checking 1092 poles.We also conducted bird tran-sects to record raptor and corvid richness and abundance,to assess species vulnerability to electrocution.Results:We recorded 76 electrocuted birds of 7 species.Electrocution rate was 6.96 birds/100 poles.The most affected species were Common Raven(Corvus corax)and Upland Buzzard(Buteo hemilasius),highlighting the electro-cution of 5 endangered Saker Falcons(Falco cherrug).By contrast,we only recorded 8 individuals of 5 species collid-ing with wires,the most affected being Pallas’s Sandgrouse(Syrrhaptes paradoxus).About 76.1%of sampled poles had some mitigation measure.Of these,96.6%were brush perch deflectors and 3.4%rotating-mirrors perch deter-rents.We found differences in electrocution rates among crossarm configurations,with the strain insulator with one jumper being the most lethal.Additionally,we found no correlation between bird abundance and electrocution rates,suggesting that some species are more sensitive to electrocution.Although no differences in total bird electrocu-tion rates were detected between poles with and without perch deterrents,when bird size is considered,deterrents reduced the mortality rate of small birds,while they were ineffective for medium-sized birds.Conclusions:Despite the widespread use of perch deterrents in the Mongolian power line network,there is still an alarming electrocution rate.This strategy is ineffective and some mechanisms,such as brush perch deflectors,may increase the electrocution rate for some medium-sized birds.Finally,we propose strategies to minimize the avian electrocution rate in the Gobi Desert.

Power Line Communications Networking Method Based on Hybrid Ant Colony and Genetic Algorithm

When solving the routing problem with traditional ant colony algorithm, there is scarce in initialize pheromone and a slow convergence and stagnation for the complex network topology and the time-varying characteristics of channel in power line carrier communication of low voltage distribution grid. The algorithm is easy to fall into premature and local optimization. Proposed an automatic network algorithm based on improved transmission delay and the load factor as the evaluation factors. With the requirements of QoS, a logical topology of power line communication network is established. By the experiment of MATLAB simulation, verify that the improved Dynamic hybrid ant colony genetic algorithm (DH_ACGA) algorithm has improved the communication performance, which solved the QoS routing problems of power communication to some extent.

Next Generation Narrowband(Under 500 kHz) Power Line Communications(PLC) Standards

In the past decade,several efforts around the world were started with the goal of introducing "smart metering" capabilities into the power grid.These efforts have spurred renewed interest in the design of next generation Narrowband Power Line Communications(NB-PLC) transceivers.In the past few years,ITU-T and IEEE have standardized a family of next generation OFDM-based NB-PLC transceivers some of which are today being considered for massive deployments in Europe and Asia.This paper addresses the important role that PLC has not only for smart metering but also for many other Smart Grid applications,and also gives an overview of the main differences between these next generation NB-PLC standards.

Correction of Observation Interference on Z component of Geomagnetic Field From DC Power Lines

为减小直流输电线路对地磁场观测的干扰,采用数学计算的方法精确求解了线路对地磁Z分量的干扰水平。以观测点为原点建立了地磁仪器观测点坐标系,推导了观测点坐标系各坐标轴在地心坐标系中的单位矢量表达式。根据空间矢量点积的定义,得到了空间电流磁场矢量投影到地磁Z分量方向的求解公式。利用推导的公式和直流线路电流磁场三维计算模型,最终求得直流线路对地磁Z分量观测的干扰水平。由此,开发了＂直流线路对地磁观测干扰校正系统＂,并开展了地磁台站和野外联合地磁观测干扰实验。结果表明,直流线路和地磁观测台站距离不超过10km时,提出的数学模型和计算方法误差不超过5%。

The design of monitoring communication system Based on Power line carrier

The design of the power line carrier communication system was introduced in this paper,DSP was adopted as the hardware platform to complete the core task.DSP sending terminal delivered the collecting data to the DSP receiving terminal through the power line carrier, and the DSP receiving terminal send the data to PC through a serial port.The design improved the power line carrier communication system and the data transmission became faster and more reliable.The experiment results showed that the PER of the receiving data is less than 0.4%, which satisfied the power line carrier communication requirement Our design is feasible and effective.

Development in Researches on Reradiation Interference from UHV Power Lines

Reradiation interference(RRI) from ultra high voltage(UHV) power lines has become a hotspot for researches in electromagnetic(EM) interference between UHV power grids and adjacent radio stations.The mechanism of RRI,numerical simulations,methods of protecting distance calculation,and resonance characteristics of RRI are reviewed in this paper using results of works reported by IEEE and Chinese publications.We conclude in this review that RRI at short and medium wavelengths can be simulated using method of moment(MoM) and two commonly used models,the wire model and the surface model,which have different applicable conditions.We indicate that the accurate simulation of RRI at higher frequencies using uniform geometrical theory of diffraction is still beyond our capability because it requires studies of the relative simulation methods.We also suggest that further researches of the mechanism of RRI and the prediction of resonance frequencies above 1.7 MHz are necessary for dealing with the interference between the existing power lines and radio stations because resonance frequencies proposed by IEEE are less than 1.7 MHz.

Power Line Monitoring Data Transmission Using Wireless Sensor Network

The WSN used in power line monitoring is long chain structure, and the bottleneck near the Sink node is more obvious. In view of this, A Sink nodes’ cooperation mechanism is presented. The Sink nodes from different WSNs are adjacently deployed. Adopting multimode and spatial multiplexing network technology, the network is constructed into multi-mode-level to achieve different levels of data streaming. The network loads are shunted and the network resources are rationally utilized. Through the multi-sink nodes cooperation, the bottlenecks at the Sink node and its near several jump nodes are solved and process the competition of communication between nodes by channel adjustment. Finally, the paper analyzed the method and provided simulation experiment results. Simulation results show that the method can solve the funnel effect of the sink node, and get a good QoS.

Phase-Locked Loop Based Cancellation of ECG Power Line Interference

Power line(PL)interference is one significant artifact in electrocardiography(ECG)that needs to be reduced to ensure accurate recording of cardiac signals.Because PL interference is non-stationary and has varying frequency,phase,and amplitude in ECG measurement,adaptive techniques are often necessary to track and cancel the interference.In this paper we present a phase-locked loop(PLL)-based adaptive filter to cancel PL interference.The PLL obtains the reference signal that is fed into the adaptive filter to remove the PL interference at the central frequency of 50 Hz.It is found that the technique can effectively cancel PL interference in real ECG signals and,when compared with some existing techniques such as least mean squares(LMS)adaptive filter,the new technique produces better results in terms of signal-to-interference ratio(SIR).

Low Complexity Discrete Bit-loading for OFDM Systems with Application in Power Line Communications

Adaptive bit-loading algorithms can improve the performance of OFDM systems significantly. The tradeoff between the performance of the algorithm and its computational complexity is essential for the implementation of loading algorithms. In this paper, we present a low complexity non-iterative discrete bit-loading algorithm to maximize the data rate subject to specified target BER and uniform power allocation. Simulation results show that the proposed algorithm outperforms the equal-BER loading and achieves similar rates to incremental allocation, yet with much lower complexity.

WAVELET-BASED OFDM-CDMA HIGH SPEED POWER LINE COMMUNICATION SYSTEMS

This letter derives the Equivalent M-band Discrete Wavelet(EMDW) transmission mode of Orthogonal Frequency Division Multiplexing(OFDM) transmission systems, and presents a new Quadrature M-band Discrete Wavelet(QMDW) based OFDM-CDMA(Code Division Multiple Access) communication systems for high speed Power Line Communication (PLC) channels.This system gives much better robustness to Inter-Channel Interference (ICI), Multi-User Interference (MUI) and noise interference, which is verified by simulation.

Modeling Transfer Function of Electrical Power Lines for Broadband Power Line Communication

The indoor access network is characterized by several branches that cause many reflections. In this paper, we present an approach to model the transfer function of electrical power lines for broadband power line communication. The assuming channel consists of three wires, which is widely used in many countries. As an application of the proposed method, the effect of line length from transmitter to receiver, branched line length and number of branched are also studied. From the frequency response of the transfer function (magnitude and phase), it is seen that the position of notches and peaks in the magnitude responses are largely affected in terms of attenuation by the electrical network which consists of 15 branches.

Data Logging and Control of a Remote Inverter Using LoRa and Power Line Communication

For decades, the power system was highly centralized. With the growing integration of distributed generations into the system, there is a necessity for bi-directional communication methods to monitor and control the remote assets. The primary objective of this paper is to develop a communication link for monitoring and controlling a grid-connected inverter in a remote location. Furthermore, the paper presents developments that have been incorporated to improve the communication link. The literature survey indicates that LoRa is superior compared to other technologies, but has some security and reliability issues. This paper also presents an encryption algorithm to improve the security of the LoRa link. Local data storage added to the system before transmitting data increases the system reliability. A display at the transmission end is added to improve the user-friendliness of the communication link. A Powerline Communication link is parallelly added to the LoRa link to improve the reliability. Finally, tests are conducted with an actual inverter and the results are presented. The tests show that the developed communication link has improved security and reliability, while its open nature makes it highly scalable and adaptable for employment in other smart grid applications.

Cross-layer Resource Allocation on Broadband Power Line Based on Novel QoS-priority Scheduling Function in MAC Layer

Traditional resource allocation algorithms use the hierarchical system, which does not apply to the bad channel environment in broadband power line communication system. Introducing the idea of cross-layer can improve the utilization of resources and ensure the QoS of services. This paper proposes a cross-layer resource allocation on broadband power line based on QoS priority scheduling function on MAC layer. Firstly, the algorithm considers both of real-time users’ requirements for delay and non-real-time users’ requirements for queue length. And then user priority function is proposed. Then each user’s scheduled packets number is calculated according to its priority function. The scheduling sequences are based on the utility function. In physical layer, according to the scheduled packets, the algorithm allocates physical resources for packets. The simulation results show that the proposed algorithm give consideration to both latency and throughput of the system with improving users’ QoS.

Application of InSAR in Surface Deformation Monitoring of Electric Power Line Selection

In the process of site selection and the facility construction in power engineering, the geological conditions of the foundation have an important impact on the displacement of completed power facilities. Usually, the conventional surface displacement has certain continuity in time and space. Therefore, in the initial stage of power line selection, the relatively stable geological conditions can greatly reduce the probability of major accidents due to ground deformation. As a new surface displacement monitoring method, InSAR can obtain the displacement monitoring results in long time series. This paper used 20 Sentinel-1A data to study the geological conditions of power line selection. Based on the fact that the vegetation coverage in the line selection area and the poor penetration of C-band data may cause serious body scattering correlation, we verified the possibility of obtaining accurate results in a long-time baseline with less influence on volume scattering decorrelation. Using this method, we obtained the surface history displacement line chart of the 220 kV power line to be erected in Laiyuan to Quanyu, Hebei Province. By analyzing 10 high coherence points on the line, we found that the largest historical surface displacement in the 18 months is less than 30mm, and the maximum cumulative deformation rate is only 12 mm/a, which meets the requirements of power line erection.