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Transmission lines are affected by aeolian vibration, sandstorms and acid rain, which cause structural damage and eventually lead to line breaking accidents. In this paper, the structural health monitoring technology of conductors is researched, and a structural monitoring system for conductors is designed. First, based on the structure of the ACSR (Aluminum Conductor Steel Reinforced) conductor and the dynamic equation, the relation between the natural frequencies and the structure of the conductor is obtained. Then, an online health monitoring system of the conductor structure is proposed, and key issues, such as the power supply solution of sensors, data preprocessing technology, multiple‐sensor synchronization method, are analyzed in detail. Finally, the structural health monitoring of overhead transmission lines designed in this paper is tested on 110‐kV experimental transmission lines. The experimental results show that from the system proposed the operation parameters of the conductors can be well obtained.

Hydrophobicity of the composite insulators is a parameter which is closely related to the insulation properties. In order to determine whether the insulator in the transmission line needs to be withdrawn, it is necessary to objectively and accurately determine the hydrophobicity grade of the composite insulator. The study on hydrophobicity detection of composite insulators of transmission lines by image analysis is proposed in this paper, by which the hydrophobicity of composite insulators can be measured timely. The grayscale, median filtering, and histogram equalization of the hydrophobic images are fulfilled sequentially, and the water drops (or water marks) region is segmented by binary large object analysis and four parameters related to water repellency are extracted. In addition, the improved support vector machine algorithm is adopted to calculate the hydrophobicity of composite insulators. The results show that seven typical hydrophobic levels of insulators can be recognized by the proposed hydrophobicity detection method whose accuracy is more than 91%.

In this article, an online monitoring technology applied to transmission line towers is proposed to overcome the problems that the foundation deformation is difficult to find in the mining area, river, hillside, and other special areas. The measurement of the stress or the strain caused by the tower foundation deformation are rarely issued, though the tower status can be possibly assessed by the stress or the strain. A new online monitoring technology of tower foundation deformation of transmission lines is developed which consists of three parts. In the first part, the stress or the strain of the key elements is effectively analyzed under the different deformations such as foundation settlement, inclination, and side-slip with the tower finite element model built and the wind load and ice load applied on the tower. In the second part, the experimental platform of tower stress tests is set up, and the internal relations between the stress variation and the tower foundation deformation are determined. In the third part, the online monitoring technology of tower foundation deformation of transmission lines is developed based on fiber Bragg grating stress sensor and successfully applied in Jibei power grid in China. The results show that all the monitored stresses fluctuating with the wind speed are small in case that the condition of tower foundation is normal; on the contrary, the corresponding stresses will change greatly.

In order to reduce the damages of transmission line icing, an effective ice accretion forecasting can be used to guide the de-icing work. The ice accretion on transmission lines varies slowly over time, and the icing data series is characteristic of timing sequence and autocorrelation. Time-series analysis is suitable for analysing the similar data series, and fireworks algorithm (FA) is used to determine the autoregressive order and the moving average order of time-series analysis. Then a short-term ice accretion forecasting for transmission lines with modified time-series analysis by FA is built. The ice accretion experiments were done in artificial icing laboratory. The results show that the modified time-series analysis model by the FA has higher accuracy than another five models, whose relative errors are

The icing on transmission line conductor usually causes accidents such as conductor galloping, conductor breaking, line tripping, and even network paralyzing, which could bring serious threats to the safe operation of the power system. The conductor icing shape not only has a great influence on the estimate to melting ice time or melting ice current, but also directly affects the mechanical calculation of conductor galloping. Therefore, it is paramount to determine the conductor icing shape. Many available artificial measurements are inaccurate and even ineffective enough in some cases. This paper proposes a novel online technology for measuring icing shape on transmission line conductor based on vision and force sensors. The proposed technique consists of three parts, namely, the online device based on vision and force sensors, the communication network, and the monitoring center. The images of the iced conductor are captured from two cameras, and the processing algorithms are used to extract the average diameters of the iced conductor. The equivalent cross-sectional area is also obtained by the force sensors and a built-in mechanics model. The icing shape description algorithm is proposed to accurately represent the icing shape. We thoroughly analyze the performance of the technology by a series of experiments under artificial icing simulations and natural conditions. The experimental results demonstrate that the proposed method can measure the icing shapes with the overlap ratio of greater than 0.85. In addition, the proposed measuring technology shows satisfactory results on the field tests carried out on operating transmission lines.

In this paper, we present a vibration-based transmission tower structural health monitoring system consisting of two parts that identifies structural changes in towers. An accelerometer group realizes vibration response acquisition at different positions and reduces the risk of data loss by data compression technology. A solar cell provides the power supply. An analyser receives the data from the acceleration sensor group and calculates the transmission tower natural frequencies, and the change in the structure is determined based on natural frequencies. Then, the data are sent to the monitoring center. Furthermore, analysis of the vibration signal and the calculation method of natural frequencies are proposed. The response and natural frequencies of vibration at different wind speeds are analysed by time-domain signal, power spectral density (PSD), root mean square (RMS) and short-time Fouier transform (STFT). The natural frequency identification of the overall structure by the stochastic subspace identification (SSI) method reveals that the number of natural frequencies that can be calculated at different wind speeds is different, but the 2nd, 3rd and 4th natural frequencies can be excited. Finally, the system was tested on a 110 kV experimental transmission line. After 18 h of experimentation, the natural frequency of the overall structure of the transmission tower was determined before and after the tower leg was lifted. The results show that before and after the tower leg is lifted, the natural frequencies of each order exhibit obvious changes, and the differences in the average values can be used as the basis for judging the structural changes of the tower.

Both practices and experiments have shown that the thermal conductivity of icing has an obvious influence on ice-melting process, but it is ignored by most of the existing models which set the simulation parameter as a constant. In this paper, an experimental study is conducted to investigate the thermal conductivity for overhead transmission line icing. Based on the test data in artificial icing laboratory, a quadratic equation of thermal conductivity and icing density is presented. And then, the equation of icing thermal conductivity is employed to simulate the critical ice-melting current and ice-melting time. The results of the experiment and simulation show that the thermal conductivity can improve the prediction accuracy in thermal de-icing projects, with the mean error of 4% and 14%, respectively.

The capacitive method is considered to be a suitable icing-detection technology, but the lack of fundamental parameters restricts the development of icing-detection sensors. In this paper, an artificial icing laboratory, a capacitive sensor, and some simulation conductors have been designed for obtaining the artificial icing samples. Subsequently, the same characteristic values of artificial icing have been measured by an LCR device, under a selected frequency. This research found that the value of the icing dielectric constant closely correlated with its density, internal sublayer, and the test temperature. Finally, a fitting formula has been presented for calculating the relative dielectric constant, which may provide some important reference value for the design of icing-detection sensors.

Transmission lines are affected by Aeolian vibration, which causes strands to break and eventually causes an entire line to break. In this paper, a method for monitoring strand breaking based on modal identification is proposed. First, the natural frequency variation of a conductor caused by strand breakage is analyzed, and a modal experiment of the LGJ-95/15 conductor is conducted. The measurement results show that the natural frequencies of the conductor decrease with an increasing number of broken strands. Next, a monitoring system incorporating a fiber Bragg grating (FBG)-based accelerometer is designed in detail. The FBG sensor is mounted on the conductor to measure the vibration signal. A wind speed sensor is used to measure the wind speed signal and is installed on the tower. An analyzer is also installed on the tower to calculate the natural frequencies, and the data are sent to the monitoring center via 3G. Finally, a monitoring system is tested on a 110 kV experimental transmission line, and the short-time Fourier transform (STFT) method and stochastic subspace identification (SSI) method are used to identify the natural frequencies of the conductor vibration. The experimental results show that SSI analysis provides a higher precision than does STFT and can extract the natural frequency under various wind speeds as an effective basis for discriminating between broken strands.

In view of the settlement problem of transmission tower foundation, the vibration characteristics of transmission towers under wind force are measured experimentally. In this paper, the 110 kV cat head transmission tower of Xi&rsquo, an Polytechnic University is measured and analyzed. Firstly, the acceleration sensor and meteorological sensor are installed on the tower to collect the vibration response and environment parameters of the tower in real time. Then, an experiment platform is built to simulate the tower settlement, and the vibration response of the tower after settlement is measured in time. Finally, the low-order modal frequencies of the transmission tower before and after settlement under wind force load are extracted by stochastic subspace identification (SSI), and the relationship between modal frequencies of different modes is analyzed via temperature correction. By comparison and analysis, it is obvious that the X-direction modal frequencies before and after settlement under natural wind load are changed, and the change rate increases with the increase of settlement displacement, which can be used as effective evidence for judging the settlement of transmission tower foundation.

The vibration of ice-shedding on overhead transmission lines will result in serious damage to tower-line system. In order to reveal the effect law of the different time parameter on the jump height of iced overhead lines after ice shedding, the conductor-insulator coupled finite element model was established, and the additional force method was employed to simulate the process of ice-shedding from overhead transmission lines, then the values of jump height were obtained for simultaneous total-span ice-shedding, unzipping ice-shedding, and assembling ice-shedding. Results from this study showed that, the difference between numerical simulation result and formula calculation result was negligible for simultaneous total-span ice-shedding. The dynamic response of unzipping ice-shedding is close to static unloading when the velocity was lower than 20m/s, the jump height was far less than calculated value by empirical formula, but the jump height of unzipping ice-shedding is close to simultaneous total-span ice-shedding effect when the velocity of ice-shedding is higher than 50m/s. The minimum jump height occurs when ΔT=T/2 for one-span assembling ice-shedding; and the maximum jump height occurs when ΔT=T/8, which may slightly greater than simultaneous total-span ice-shedding because of conductor coupling effect.

Composite insulator has been widely used in high-voltage power system; besides, its service life is getting longer and longer. Accordingly, the aging of the composite insulator has been paid more and more attention by the people, and how to comprehensive evaluate the aging state of composite insulator in service is great important to ensure the reliability of the transmission line. In this paper, the nodal discontinuous Galerkin method is for the first time used to analyze the electric field distribution on the surface of composite insulator, and the deformation of composite insulator is analyzed by the finite element method. Based on the numerical analysis for the surface electric field distribution and deformation of the composite insulator, the operation state of which is evaluated, and then it will help establishing a new method for evaluating the operation state of composite insulators and high-voltage tower, and a collective evaluating model for completing the aging properties of composite insulators. Finally, an on-line monitoring method is designed to monitor the deformation of the insulator by the strain gauge embedded in the composite insulator surface, thus monitoring the running state of insulator strings in real time.

The measurement of the amplitude and phase of the transmission line is the key technology which can monitor the insulated condition of all kinds of capacitive equipment or Zinc Oxide Arrester. However, it is short of the valid method measuring the phase of the transmission line in the outdoors. This paper puts forward a technology that can measure the phase of the tri-phase transmission line, to gain the voltage and the phase by the electric-field sensor, and finally achieve the phase of each phase transmission line through the method which can separate the phase from the superimposed electric-field. A lot of tests indicate that the phase precision can reach to 0.5 degrees. It can realize the insulation online monitoring of the capacitive equipment or Zinc Oxide Arrester by using the technology combined with the current transformer.

In view of the problems of electromagnetic interference, power supply instability and short service life of existing transmission line condition monitoring devices, this paper develops an integrated condition monitoring system of transmission lines based on fiber bragg grating sensors. This system uses fiber bragg grating strain sensor, tension sensor, temperature sensor and vibration sensor to measure the tower strain, wire tension, wire temperature and Aeolian vibration, and sends the optical signals to the fiber bragg grating demodulator of the substation through OPGW. This system can realize the passive measurement of the running condition of the wire, and there will be no power supply problems. In addition, combining with the characteristics of anti-electromagnetic interference and high precision of the fiber bragg grating sensors, the stability and reliability of the system are improved.

With the speeding up of the power grid construction, accidents on transmission lines have also occurred frequently, such as: icing lines, conductor galloping, aerolian vibration, windage yaw and wires sag etc. Therefore, it is of great importance to make online monitoring and fault diagnosis for transmission lines comprehensive state with using intelligent monitoring device. At present, the study about the transmission wires state has made very big progress home and abroad, but the low accuracy of the collecting information, the unreliable power supply, the inconvenient installation and other technical problems are still exist. Aiming at the existing technical problems, an intelligent on-line condition monitoring system for transmission lines comprehensive state is put forward in this subject research, it is through the latest sensor technology that various sensors for wires state measurement are integrated, and information of transmission lines is timely collected to ensure the safety of the power transmission. According to the test results, various information of transmission lines state can be accurately collected by the measurement method in this system, and the monitoring device can be installed conveniently, meanwhile it contributes to early detect hidden danger and remove the faults in time, so as to improve the reliability of the transmission line operation.

The shortage of the existing on-line monitoring technology of transmission line conductor icing at home and abroad was analyzed, and the necessity of improving the existing icing monitoring technology was pointed out in this paper. The new on-line monitoring system of transmission line conductor icing was designed. The master-slave monitoring structure was used in the whole system design. In this paper, the new system structure and technical features were briefly described, a new mechanical model of computing icing coating was built, and the calculation method of conductor icing density and type was given in details. The testing and running results show that the shortage of existing on-line monitor technology of transmission line conductor icing can be improved by this new on-line monitoring technology what is more effective to guide the icing transmission lines de-icing.

Based on the analyses of the disadvantages and advantages of every on-line monitoring system of transmission line's galloping, an on-line monitoring system of power transmission line's galloping based on displacement sensors and acceleration sensors is developed in this paper, in which the wireless sensors network and the slave monitoring unit installed on towers are designed by wireless communication technique, by those monitoring units the galloping can be analyzed qualitatively and quantitatively. The operating principle, structure and function of the system are all analyzed at the same time. Moreover, the designation of the node of wireless sensors network based on ZigBee technique and the slave monitoring unit installed on towers are all shown in detailed in this paper. Based on the galloping mechanism as well as earlier data, the galloping is simulated in theory, and then some simulating results are shown in this paper at last.

An on-line monitoring system of transmission line conductor de-icing based on GSM SMS and Zigbee is firstly designed and produced, the composition and the technical features of which are described. The meteorology such as the temperature, the humidity, the wind speed, the rain and snow, and the air pressure etc., the icing status of transmission lines such as the gravity of iced conductors, the deflection angel of insulators, the deviation angel of insulators for wind, gallop frequency of conductors etc., and the temperature of running conductors are measured by the system, by which the study on the de-icing properties and the temperature rising properties can be made. The beginning, the process and the effect of de-icing can be controlled automatically.

The on-line monitoring system for transmission line conductor icing and galloping is developed based on GSM SMS, the theoretical computation model of icing coating and radian variation of conductors is built, and the installation construction of force sensors is shown in figure. The running results show that the on-line monitoring unit placed on every transmission line tower timely measures the tower force, the deviation angel of insulators for wind, the deflection angel of insulators, the environmental temperature, the environmental humidity, the wind velocity and the wind direction etc. and sends the above information to the municipal monitoring and controlling center by SMS. The conductor icing and galloping is computed based on the theoretical computation model built firstly, the alarm message of clearing conductor icing is sent out on time, and the safe operation of transmission line is effectively guaranteed. (6 pages)