Optical Fiber Composite Overhead Ground Wire Research Articles

A Fast and Accurate Mapping Method for an OPGW Tower Based on Hybrid Distributed Optical Fiber Sensing.

The combination of the dark fiber in existing Optical Fiber Composite Overhead Ground Wire (OPGW) with Distributed Optical Fiber Sensing (DOFS) technology can be used to enable online monitoring and provide early warnings of anomalies in high-voltage transmission lines. Accurate mapping of the optical cable length to the geographic coordinates of actual towers is a key factor in achieving this goal. This paper discusses the principle of using a DOFS system for transmission line tower positioning and presents four available positioning features. To overcome the limitations of single physical parameter positioning, this paper presents a self-developed hybrid DOFS that simultaneously captures Rayleigh backscattering and Brillouin scattering signals. Several physical parameters, including temperature, strain, and vibration, are acquired synchronously. Through hybrid multi-parameter analysis, the rapid and accurate positioning of OPGW line towers is achieved. Experimental results have shown that the proposed method, based on the hybrid DOFS system, can locate up to 82 towers, while the traditional method could only identify 12. The hybrid system was able to complete 80% of the tension towers in 40 h. This paper presents a novel multi-parameter localization method that has the potential to significantly improve the efficiency and reliability of grid operation and maintenance.

High precision three-dimensional ellipse fitting correction for galloping monitoring

In this paper, we propose and demonstrate a high precision three-dimensional (3D) ellipse fitting correction method for optical fiber composite overhead ground wire (OPGW) galloping monitoring, based on weak fiber Bragg grating array. 3D ellipse formed by three outputs of the system is fitted by the coordinate rotation and least square methods, and direct current (DC) components and alternate current (AC) component coefficients of the three outputs are obtained. By differentiating and cross-multiplying the three outputs, those DC components are zeroized, AC component coefficients are normalized, and finally, the interference phase signal is calculated. The experimental results show that the proposed method can demodulate the vibration signals better, and the fitted R2 is above 0.99. The system is implemented on a 220 kV transmission line in the plateau region of Western China, forecasting a galloping period with a wavelength of about 60 m within the span accurately. This method demonstrates suitability for monitoring OPGW transmission line galloping events.

Method for lightning flashover types identification on transmission lines utilizing OPGW optical polarization state signal characteristics

The Optical Fiber Composite Overhead Ground Wire (OPGW) has undergone rapid development and has been extensively applied in the realm of intelligent power system status monitoring. This article conducts research on lightning signal waveform in optical fibers within the context of lightning fault location using the OPGW optical polarization state method. A transmission line model is simulated employing ATP-EMTP to capture electrical characteristics when lightning strikes the OPGW. Subsequently, by employing the Faraday magneto-optical effect principle, electrical signals are transformed into optical polarization states within the internal fibers of OPGW. Using such data, the optical signal propagation characteristics when lightning strikes OPGW are deduced. Finally, a method for discerning between induced lightning and direct lightning strikes through the analysis of time-frequency domain characteristics in OPGW. This method addresses the limitation of traditional OPGW lightning monitoring, which is unable to deduce electrical signals, thus achieving precise identification of lightning-induced transient faults in transmission lines.

OPGW positioning and early warning method based on a Brillouin distributed optical fiber sensor and machine learning.

A method of optical fiber composite overhead ground wire (OPGW) positioning based on a Brillouin distributed optical fiber sensor and machine learning is proposed. A distributed Brillouin optical time-domain reflectometry (BOTDR) and Brillouin optical time-domain analyzer (BOTDA) are designed, where the ranges of BOTDR and the BOTDA are 110km and 125km, respectively. An unsupervised machine learning method density-based spatial clustering of applications with noise (DBSCAN) is proposed to automatically identify the splicing point based on the Brillouin frequency shift (BFS) difference of adjacent sections. An adaptive parameter selection method based on k-distance is adapted to overcome the parameter sensitivity. The validity of the proposed DBSCAN algorithm is greater than 96%, which is evaluated by three commonly external validation indices with five typical BFS curves. According to the clustering results of different fiber cores and the tower schedule of the OPGW, the connecting towers are distinguished, which is proved as a 100% recognition rate. According to the identification results of different fiber cores of both the OPGW cables and tower schedule, the connecting towers can be distinguished, and the distributed strain information is extracted directly from the BFS to strain. The abnormal region is positioned and warned according to the distributed strain measurements. The method proposed herein significantly improves the efficiency of fault positioning and early warning, which means a higher operational reliability of the OPGW cables.

Secure Data Processing Technology of Distribution Network OPGW Line with Edge Computing

Promoted by information technology and scalable information systems, the network design and communication method of optical fiber composite overhead ground wire (OPGW) have been in great progress recently. As the overhead transmission line has strict requirements on the outer diameter and weight of OPGW, it is of vital importance to perform the physical-layer secure data processing for the distribution network OPGW line with edge computing. To this end, we examine a physical-layer secure distribution network OPGW with edge computing in this article, where there exists one transmitter S, one receiver D, one authorized legitimate monitor LM, and an interfering node I. To better analyze the system performance, we firstly give the definition of the system outage probability, based on the secure data rate. Then, we evaluate the system performance for the distribution network OPGW, by deriving analytical outage probability of secure data processing, to facilitate the system performance evaluation of secure data processing in the entire SNR regime. Finally, we demonstrate some simulation results to validate the analytical results on the physical-layer secure distribution network OPGW line with edge computing.

Research on Communication Technology of OPGW Line in Distribution Network under Interference Environment

In optical fiber composite overhead ground wire (OPGW) networks, the current monitoring is mainly through installing electronic sensors on the cable and manually monitoring the video on the cable, where the interference plays an important role in the communication and monitoring based systems. In essence, the interference arises from aggressive frequency reuse, especially in the frequency-limited Internet of Things (IoT) networks. The existence of interference causes a negative effect on the system performance of communication systems and IoT networks including the OPGW networks. Hence, this article investigates the communication technology of OPGW line in distribution network under interference environment, where there is one primary link, one secondary link, and one legitimate monitor listening to the secondary link. The secondary user needs to transmit its message to the secondary receiver under the interference power constrained by the primary node. We firstly define the outage probability of legitimate monitoring based on the data rate, and then analyze the system performance by theoretically deriving a closed-form expression of the outage probability for the OPGW communication under interference environment. Simulation results are finally demonstrated to verify the correctness of the closed-form expression for the OPGW communication under interference environment, and show that the interference has a negative impact on the OPGW communication performance.

Two-Way Data Processing Technology for OPGW Line of Distribution Power Communication Networks

Promoted by information technology and scalable information systems, optical fiber composite overhead ground wire (OPGW) can not only improve the use efficiency of power towers, but also give full play to the dual role of communication optical cable and ground wire, due to the advantages of high reliability, excellent mechanical performance and low cost. The effective processing of the data from OPGW can effectively promote the wide application. In this paper, we study the two-way data processing technology for OPGW line of distribution power communication networks, where a single relay node assists the two-way data processing in time-division multiplexing mode. We evaluate the influence of the model parameters on the system data processing performance by investigating the outage probability, whereas the analytical and simulation results are demonstrated to show the effectiveness of two-way data processing for the OPGW communication. The results in this paper provides important reference for the development of OPGW communication and scalable information systems.

Research on Optical Fiber Composite Overhead Wire (OPGW) Lightning Monitoring Technology Based on Weak Fiber Bragg Grating Array

Optical fiber composite overhead ground wire (OPGW), which consists of ground wire and communication function, has been widely used in transmission lines. Its running state is directly related to the security of power grid communication. In reality, the main environmental factors leading to OPGW malfunction include icing, mountain fire, wind vibration, etc., especially lightning stroke. In this paper, an OPGW temperature monitoring method based on Weak Fiber Bragg Grating (WFBG) array is proposed. By monitoring the temperature change caused by lightning stroke, the lightning stroke level identification and lightning stroke location are realized. The test results show that the minimum lightning discharge identification can reach to 9 C and the lightning location resolution is better than 0.1 m. Compared with other lightning temperature monitoring methods, lightning grade identification and positioning accuracy can be improved by this method, and it has the advantages of high real-time FBG, which provides a new approach for lightning monitoring of OPGW.

Phi-OTDR Based On-Line Monitoring of Overhead Power Transmission Line

The overhead power transmission line, as an important component of equipment for long-distance power transmission, is threatened by icing and galloping, which will lead to equipment troubles and cause huge economic loss. Thus, there is a great need for on-line monitoring for transmission lines. Because the photoelectric composite cable, such as optical fiber composite overhead ground wire (OPGW) is widely used, it is possible to introduce distributed optical fiber sensors (DOFS) into transmission line status monitoring. Common schemes based on DOFS usually offer low sensing density and are hard to realize global awareness, while phase sensitive optical time domain reflectometry (Φ-OTDR), as a DOFS that has the characteristic of distributed sensing, is hoping to address the limitation. In this paper, by establishing mathematical models, proposing analytical method, and building demonstration devices to analyze the dynamic strain characteristics of overhead power transmission line, an Φ-OTDR based on-line monitoring scheme of transmission line status is presented and experimentally proved for the first time. The estimation error of sag is less than 5.8% on centimeter scale, and the estimation error of ice thickness is no more than 10.84% on sub-millimeter scale, which gives an accurate description of transmission line status and provides strong support for early warning of transmission line failures.

Distributed Transmission Line Ice-Coating Recognition System Based on BOTDR Temperature Monitoring

An optical fiber composite overhead ground wire (OPGW) distributed ice-coating monitoring scheme based on Brillouin optical time domain reflectometer (BOTDR) temperature measurement is proposed and demonstrated. The thermodynamic factors affecting the temperature of the OPGW cable are analyzed, and the temperature variation characteristics of the icing and non-icing sections of the OPGW cable with different icing thicknesses are analyzed via finite-element analysis. The results of an OPGW icing experiment indicate that when the ambient temperature changes, there is an obvious hysteresis characteristic between the temperature changes of the icing and non-icing sections of the OPGW cable, which is related to the thickness of the ice. Thus, we propose a distributed OPGW cable icing monitoring system based on BOTDR temperature monitoring.

Calculation and Analysis of Induced Current in Optical Fiber Composite Overhead Ground Wire

In this paper, the mechanism of electromagnetic induction current of overhead ground wire is analyzed, the models of overhead ground wire with different voltage levels are established on ATP-EMTP, the electromagnetic induction current of optical fiber composite overhead ground wire (OPGW) is calculated, and the factors affecting the induced current on OPGW are analyzed, including the change in loads of transmission lines, the value of grounding resistance and the location of lines. The results of this paper provide a reference for the actual measurement and the use of this induced current for induction power supply.

On-situ monitoring of sleet-thawing for OPGW based on long distance BOTDR

With the absence of on-situ temperature monitoring of optical fiber composite overhead ground wire (OPGW) for the process of sleet-thawing, early temperature warning and safety control of direct current (DC) in sleet-thawing process is difficult. Here we propose a Brillouin optical time-domain reflectometry (BOTDR) with broadband receiving for fast measurement and with distributed Raman amplification for long distance measurement of about 100 km. A field experiment for on-situ temperature monitoring of sleet-thawing of OPGW is also reported, which shows uneven change of temperature along the OPGW. The difference between the maximum and the minimum temperature change can be greater than 40 °C.

Insulation Reconstruction for OPGW DC De-Icing and Its Influence on Lightning Protection and Energy Conservation

In order to satisfy demands for DC de-icing of optical fiber composite overhead ground wire (OPGW) and solve questions such as those relating to circulating current loss and liability of suffering from lightning strike, the grounding method of OPGW must be changed from the current commonly used method of being grounded at every tower to being grounded at one tower. The OPGW would be connected to the tower by an insulator, which is often shunt connected with a protective discharge clearance. The recommended value of the discharge clearance is from 70 to 80 mm. The lightning impulse discharge voltage of such a clearance is generally not more than 100 kV. However, as the transmission line is struck by lightning, over-voltage on the clearance is 885 kV at least, even up to a few MV. The clearance can be broken down reliably. The influence of insulation reconstruction for OPGW on the induced current and the power loss of the AC transmission line was studied by means of theoretical analysis and simulation calculations. Results indicate that change of the OPGW grounding mode could reduce the induced current of the ground wire to below 1 A and reduce the power loss of the line to below 1 W/km. Power loss could be reduced by over 99%. Adoption of a suitable grounding mode for OPGW is of great significance for DC de-icing, lightning protection safety, and energy savings for UHV projects.

Analysis of Operation and Maintenance of Optical Fiber Communication System

With the development of the times, the use of optical fiber network communication is widely used in power communication, most power plants through optical fiber technology to improve the level of power transport and power security. ADSS (All-dielectric Self-supporting Optical Cable) and OPGW (Optical Fiber Composite Overhead Ground Wire) are the most widely used optical fibers in power systems.

A Programme to Solution the Problem of OPGW Substation Structure Grounding

OPGW with functions of lighting proof and communication is widely used in the construction of power network. For optical fiber composite overhead ground wire (OPGW), it is required to achieve the separation of wire and signal after the introduction of the substation structure[1]; at the same time, the grounding for lightning proof is also required because of the frequent occurrence of the burnout of the optical cable and short circuit due to the electric discharge and lighting as a result of the problems in the grounding device or construction. This paper analysis some common advantages and disadvantages of OPGW structure grounding methods. In combination with the practical conditions of the project, the solution “Enhanced the grounding method” is brought up and solve the practical problem.

An adaptive security protocol for a wireless sensor‐based monitoring network in smart grid transmission lines

AbstractIn this paper, we propose a new security protocol for a wireless sensor network, which is designed for monitoring long range power transmission lines in smart grid. Part of the monitoring network is composed of optical fiber composite over head ground wire (OPGW), thus it can be secured with conventional security protocol. However, the wireless sensor network between two neighboring OPGW gateways remains vulnerable. Our proposed security protocol focuses on the wireless sensor network part, it provides mutual authentication, data integrity, and data confidentiality for both uplink and downlink transmissions between the sensor nodes and the OPGW gateway. Besides, our proposed protocol is adaptive to the dynamic node changes of the monitoring sensor network; for example, new sensors are added to the network, or some of the sensors are malfunctioning. We further propose a self‐healing process using an “i‐neighboring nodes” public key structure and an asymmetric algorithm. We also conduct energy consumption analysis for both general and extreme conditions to show that our security protocol improves the availability of the monitoring sensor network. Copyright © 2015 John Wiley & Sons, Ltd.

Design and analysis of a wireless monitoring network for transmission lines in smart grid

AbstractIn order to timely and precisely locate a problem over the power lines, the control center needs to monitor the status of the transmissionlines and the towers. In this paper, we design such a monitoring network by taking advantage of the existing optical fiber composite overhead ground wire (OPGW) alongside the transmission lines. Because it is not cost‐effective to have gateway access to the OPGW for every transmission tower, we propose to deploy a multi‐hop wireless sensor network in between two sparsely deployed neighboring OPGW gateways. We mainly study the power allocation for the data transmission of the wireless sensors because of the assumption that such sensors are powered by green energy and a battery with limited capacity for easy deployment and maintenance. Specifically, we propose several centralized schemes with different objectives, for example, the minimum power usage and fast computation. We also propose a distributed scheme so that the sensors can be even more energy efficient dealing with dynamic traffic in field operations. Moreover, we analyze the centralized schemes to study their pros and cons. We also conduct a case study for the distributed scheme to demonstrate its feasibility in field operations. Copyright © 2015 John Wiley & Sons, Ltd.

基于氮化铝的OPGW交流融冰效率的研究

输电线路覆冰事故严重威胁电网安全运行，抗冰防灾是电网建设的重点攻克技术之一，其中，地线融冰研究是常用的关键技术。基于复合光架空地线两层层绞式结构，采用无感双绞线作为融冰热源，实现对地线覆冰段交流融冰。本文采用高热导率半导体材料氮化铝填充导线层间空气气隙，提高融冰传热速度，缩短融冰时间，减少融冰热损耗，有效改进OPGW融冰效率。结合热路分析法，理论计算氮化铝提高融冰效率。制作OPGW交流融冰样品及氮化铝样品，实验得到两种样品融冰时间，对比分析氮化铝提高融冰效率是可行的。Ice accident on transmission lines influences the safe operation of power grid. Preventing ice dis-aster is one of the key technologies for the construction of power network. Ground wire ice-melt- ing technology is of great significance in conventional technology. Based on the layer stranded structure of Optical Fiber Composite Overhead Ground Wire (OPGW), a twisted bifilar wire fabricated by insulated wire is used as a heater for AC de-icing of ground wire. In order to enhance the heat transfer rate and shorten the ice-melting time as well as reduce the heat loss and improve ice melting efficiency, aluminum nitride, a semiconductor with high thermal conductivity, is used to fill in the gap among the conductor. An equivalent thermal circuit is established to calculate the de-icing efficiency of OPGW with aluminum nitride. With the samples of ice melting conductors, the ice melting time is analyzed based on de-icing conditions. It is confirmed that the ice melting efficiency of OPGW can be feasibly improved by filling the aluminum nitride.

Research of Communication Technology on IOT for High-Voltage Transmission Line

This paper presents a three layered network construction of Internet of Things (IOT) communication method for high-voltage transmission line which involves the wireless self-organized sensor network (WSN), optical fiber composite overhead ground wire (OPGW), general packet radio service (GPRS) and the Beidou (COMPASS) navigation satellite system (CNSS). The function of each layer of network, application deployment and management of energy consumption are studied. The method can meet the needs of interconnection between the monitoring center and terminals, reduce the terminals’ GPRS and CNSS configuration and OPGW optical access points, and ensure the on-line monitoring data transmission real-time and reliable under the situation of remote region, extreme weather and other environmental conditions.