oTemperature tracer method in structural health monitoring: a review

Detection of acoustic signals is an effective approach for online-monitoring of the power equipment. However, the signal-to-noise ratio of the acoustic detection system is limited by the noisy and harsh environment around the power equipment. In this study, an acoustic detection system based on resonant-enhanced acquisition is proposed. By utilizing a horn-shaped acoustic resonator with multiple resonant frequencies, the proposed system can realize long-distance acoustic sensing with high sensitivity in both the audible and ultrasonic ranges. The sensitivity of the system in the designated frequencies is enhanced by 28 dB, while the signal-to-noise ratio increased by 14.1 dB. Integrated with a control terminal, the system can perform complex functionality, e.g., record and analyze the acoustic information and provide visual/audible feedback for human operators. The proposed system can be considered as a technological platform for the acoustic fault diagnosis of power equipment. 

A portable industrial acoustic detection system with multiband resonant amplification

On-board transformer is one of the important components in vehicle-mounted mobile substations for power supply. The features of electromagnetic vibrations of on-board transformer are closely related to the mechanical condition monitoring and the mechanical structure optimization. In this paper, the electromagnetic vibration of the OSFP11-120000/230 type on-board transformer is calculated with a 3D model through the finite element method. The magnetic flux density and electromagnetic forces of winding and core of on-board transformer are analyzed by a field circuit finite coupling element. Through the direct electromagnetic-structure coupling method, the winding vibration and core vibration of on-board are calculated. It is that the distribution of magnetostrictive force is basically similar to the magnetic flux of on-board transformer. The axial vibrations of transformer winding reach the largest at 1/4 and 3/4 positions with a main frequency spectrum of 100Hz. The radial vibration of transformer winding reaches the largest at the 1/2 position and the whole vibration strength is smaller than those of axial vibration. The core vibrations in each part are different with relatively rich frequency spectrum components.

Finite Element Analysis of Electromagnetic Vibration in Large Capacity On-board Transformer

On-board transformer is one of the important components in vehicle-mounted mobile substations for power supply. The features of electromagnetic vibrations of on-board transformer are closely related to the mechanical condition monitoring and the mechanical structure optimization. In this paper, the electromagnetic vibration of the OSFP11-120000/230 type on-board transformer is calculated with a 3D model through the finite element method. The magnetic flux density and electromagnetic forces of winding and core of on-board transformer are analyzed by a field circuit finite coupling element. Through the direct electromagnetic-structure coupling method, the winding vibration and core vibration of on-board are calculated. It is that the distribution of magnetostrictive force is basically similar to the magnetic flux of on-board transformer. The axial vibrations of transformer winding reach the largest at 1/4 and 3/4 positions with a main frequency spectrum of 100Hz. The radial vibration of transformer winding reaches the largest at the 1/2 position and the whole vibration strength is smaller than those of axial vibration. The core vibrations in each part are different with relatively rich frequency spectrum components. 

Detection of acoustic signals is an effective approach for online monitoring of power equipment. However, the signal-to-noise ratio (SNR) of the acoustic detection system is limited by the noisy and harsh environment around the power equipment. In this study, an acoustic detection system based on resonant-enhanced acquisition is proposed. By utilizing a horn-shaped acoustic resonator with multiple resonant frequencies, the proposed system can realize long-distance acoustic sensing with high sensitivity in both the audible and ultrasonic ranges. The sensitivity of the system in the designated frequencies is enhanced by 28 dB, while the SNR increased by 14.1 dB. Integrated with a control terminal, the system can perform complex functionality, e.g., record and analyze the acoustic information and provide visual/audible feedback for human operators. The proposed system can be considered a technological platform for the acoustic fault diagnosis of power equipment.

A Portable Industrial Acoustic Detection System With Multiband Resonant Amplification

The variation of magnetic state of transformer often causes the violent vibration of the transformer various parts, especially the core. The most obvious magnetic state change of the transformer is usually caused by the dc component. In this article, one kind of magnetic compensation method is adopted to suppress the dc bias, and the core vibration caused by the transformer magnetic state change is studied in detail. At first, on the basis of measuring the magnetostriction and calculating the vibration displacement of transformer core, the research on the vibration increment created by the dc bias is carried out. Second, the transformer core vibration before and after the dc bias suppression is simulated, and the difference of the transformer with a magnetic compensation capacity is analyzed. Finally, based on the VIBXPERT1II FFT data acquisition and signal analyzer, the vibration of measuring points under the different magnetic state and the different measuring point under the same magnetic state are collected. The vibration tendency of each measuring point is given with the variation of the magnetic state. Thus, the vulnerable spot of the core vibration and the basic law of the transformer vibration are obtained, which could provide a basic method for the reducing vibration.1Registered Trademark.

Influence of Magnetic State Variation on Transformer Core Vibration Characteristics and Its Measurement

Here, a method for assessing the risk of bird pecking damage of composite insulators in ultra high voltage (UHV) lines is proposed using electric field (E-field) simulation and deep learning. The distribution of E-field on composite insulators is analysed via numerical simulation for different damage locations and damage sizes. Then, using the defective images of composite insulator strings captured in real inspection environments, the corresponding annotation image data set is constructed according to the finite element calculation results of E-field under different damage conditions, and through the application of the YOLOX deep learning neural network, the risk assessment of the damage caused by bird pecking of insulators for UHV lines is conducted. Furthermore, to prevent overfitting of YOLOX with small-scale images, transfer learning, as well as data enhancement, are applied to the YOLOX training process. According to the results, the mean average precision (mAP) of the model is 0.79, indicating that it is capable of high accuracy recognition, provides guidance for operation and maintenance personnel. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1049/gtd2.12853

Bird pecking damage risk assessment of UHV transmission line composite insulators based on deep learning

When the power transformer is connected to power grids, due to the existing remanent magnetism (RM) and the voltage transient component, the transformer will generate a large magnetizing inrush current (MIC). The MIC not only seriously threatens the safe operation of the transformer, but also causes the misoperation in the differential protections. To solve the aforementioned problems, a novel MIC elimination strategy of the hybrid transformer (HT) based on an asynchronous closing technology is proposed in this article. First, through the rational design of the HT topology, the parallel auxiliary winding (PAW) of the HT is established and the magnetic coupling mechanism is realized, which lay the magnetic circuit foundation for the MIC management. Second, a step-type synchronous magnetic field is established through PAW without considering RM. After the action of step-type magnetic field, the core flux increases sinusoidal linearly and enters into the rated steady stable. Finally, by controlling the stabilization time of the oblique wave and the primary voltage signal of the power grid, when the core flux is stabilized, the nonsynchronous closing of the HT can effectively alleviate the generation of the MIC. The validity and feasibility of the proposed scheme are verified by building an HT prototype platform, which provides some reference for the difficulty of measuring RM and avoiding MIC in the power system.

Magnetizing Inrush Current Elimination Strategy Based on a Parallel Type Asynchronous Closing Hybrid Transformer

The UHV eight-wire lifter is an important tool in frequent use for the construction and maintenance of UHV transmission lines, which is made of titanium alloy and weighs about 40 kg. Due to high-weight, the work efficiency is greatly reduced. In this paper, the design of a lightweight UHV eight-wire lifter is proposed by using carbon fiber cladding structure. The effects of three factors on the maximum load-bearing load of the carbon fiber exterior cladding structural member are excavated through the failed experiment of the carbon fiber exterior cladding tensile and shear test pieces and the finite element progressive damage numerical calculation. The orthogonal experiment is employed to obtain the optimal cladding structure of the eight-wire lifter with a carbon fiber exterior coating cladding. After that, carbon fiber eight-wire lifter is developed and subjected to mechanical tests. The test results show that the performance of carbon fiber eight-wire lifter meets the mechanical performance requirements of eight-wire lifter. Compared with the titanium alloy eight-wire lifter, the maximum load-bearing load of the carbon fiber eight-wire lifter is increased by 20.5%, and the weight is decreased by 37.5%.

Design and optimization of carbon fiber eight-wire lifter with exterior cladding structure

The application potential of aluminium conductor composite core (ACCC) conductors in the 1000-kV power transmission line project deserves to be investigated. Its economic evaluation is a contentious issue. This paper proposes a method for selecting the type of conductors based on the life cycle cost (LCC) of a transmission line, which includes the initial investments, operation costs, maintenance costs, failure costs, and discard costs. The mathematical model of electromagnetic loss differs due to the various operational circumstances surrounding a transmission line; therefore, a novel three-dimensional electromagnetic–fluid–thermal coupling model based on the finite element method (FEM) was proposed. The simulation error of ACCC and aluminium conductor steel reinforced (ACSR) conductors is 2.56% and 0.5%, respectively, compared to the experimental value. Subsequently, the LCC model is applied in the economic analysis of a 1000-kV transmission line, and the costs of ACCC conductors and ACSR conductors under different annual power load utilization hours are calculated. The results indicate that the overhead power transmission line with ACCC conductors saves at least 2 × 106 ¥/km compared with ACSR when annual utilization hours reach 3500 h; meanwhile, energy saving benefits are achieved. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1049/gtd2.12719

Economic analysis of aluminium conductor composite core and conventional aluminium conductor steel reinforced conductors in overhead ultra‐high voltage transmission lines

Yujiao Zhang

Papers

Influence of Magnetic State Variation on Transformer Core Vibration Characteristics and Its Measurement

Bird pecking damage risk assessment of UHV transmission line composite insulators based on deep learning

Magnetizing Inrush Current Elimination Strategy Based on a Parallel Type Asynchronous Closing Hybrid Transformer

Design and optimization of carbon fiber eight-wire lifter with exterior cladding structure

Economic analysis of aluminium conductor composite core and conventional aluminium conductor steel reinforced conductors in overhead ultra‐high voltage transmission lines