Research of thermal endurance of cables of secondary systems of TsGPP substation under short-circuit conditions

The article presents the results of research on thermal endurance of control cables of secondary systems of substation 500 kV “TsGPP” substation under single-phase short circuits (SC). The study is based on the combination of field experiments and numerical modeling of the computational model of the grounding, which determines the distribution of potentials on the grounding and currents on the cable shields. The results showed that when a short-circuit occurs on the OS (Outdoor Switchgear)-220 kV and OS-110 kV current density flowing through the screen may exceed the permissible values, which leads to thermal damage to cables and, as a result, an increased risk of damage to the secondary relay protection and control systems. Based on the analysis of the obtained data, recommendations for optimizing the configuration of the grounding have been proposed. Densification of local grounding and an increase in the number of connections between the shield grounding and the grounding grid leads to a reduction in the potential distribution gradient in the grounding circuit of the “TsGPP” substation. Given the soil resistivity parameters specific to the substation under study, the current levels flowing through the control cable screens have been reduced to values below the established permissible thresholds. For the first time, the results of research conducted at an actual high-voltage substation have demonstrated the feasibility of ensuring the thermal stability of control cables through the reconstruction of the grounding

A method for automatically extracting harmonic features and its application in fault diagnosis of rolling bearing

With regard to fault diagnosis of rolling bearing, the envelope demodulation method is usually used to analyze the original vibration signal of faulty bearing, then the fault location of the bearing is determined by examining the distributions of fault characteristic frequencies, harmonics and sideband on the envelope demodulation spectral. The fault characteristic frequency with its harmonics could not be extracted by this traditional method when the original vibration signal is contaminated heavily by background noise. Besides, this method needs high professional knowledge and will expose drawbacks such as complex work, low diagnostic efficiency and so on while dealing with a large number of faulty bearings in engineering application. To solve the above problems, this paper proposes an automatic harmonic feature extraction method. Firstly, a series of bandpass filters are obtained based on fast Kurtogram, and then the original signal is filtered by the series of bandpass filters. The series of filtered signals are subjected to envelope analysis and noise reduction processing. Finally, the denoised series of envelope results are processed by the proposed algorithm for extracting the number of harmonics, harmonic intensity, and harmonic intensity index, and the target feature frequency and its harmonic components hidden in the original signal is extracted automatically. A simulation case and an engineering case verify that the proposed method can not only automatically calculate the number of harmonics of the characteristic frequencies, but also calculate the corresponding harmonic intensity, providing more effective and efficient feature support for fault diagnosis of bearing

Research on rockfall scratch damage of FRP-coated oil and gas pipelines based on finite element method

Oil and gas pipelines, as vital arteries for energy transportation, play a crucial role in ensuring the supply of energy. However, under harsh geological conditions and external forces, the pipeline's anti-corrosion layer is susceptible to damage, particularly the destruction caused by external forces such as rockfall. This study focuses on the performance of a new type of anti-corrosion material-Fiber Reinforced Polymer (FRP) coating-under rockfall scratch, and compares it with Polyethylene (3PE) coating. By establishing a three-dimensional finite element model of the pipeline and rockfall, the study simulates the scratch process of rockfall on FRP and 3PE coated pipelines, analyzing the impact of various parameters on the coating damage. The results indicate that the FRP coating has a significant advantage in resisting rockfall damage, effectively dispersing and absorbing the impact force, thereby reducing damage. Moreover, parameters such as rockfall moving velocity, angle, penetration depth, and coating thickness significantly affect the degree of damage to the FRP coating. This research provides theoretical basis and technical support for the protection of oil and gas pipelines, which is of great importance for enhancing the safety and reliability of pipelines

Influence of the supporting surface inclination angle on the locomotion conditions of a vibration-driven system

This paper investigates the influence of supporting surface inclination angle on the locomotion of a capsule-type robot driven by an imbalanced rotor, considering dry anisotropic friction. Using Lagrange’s second-order differential equations, a mathematical model is developed, and numerical simulations are performed with Wolfram Mathematica software. The scientific novelty lies in the comprehensive analysis of how inclination angle, coupled with anisotropic friction, affects the capsule’s motion, including the derivation of analytical conditions for maintaining a “non-detachable” motion regime and preventing backward slippage. Key results include the establishment of relationships for the maximum permissible angular velocity of the imbalanced rotor as a function of surface inclination angle and friction coefficient. It is found that this velocity is maximal on horizontal surfaces and decreases with increasing inclination, while higher backward friction coefficients allow for greater rotor speeds. The practical value of these findings is significant for the design and control of vibration-driven robots, particularly for applications such as pipeline inspection, monitoring, and cleaning, where reliable navigation across varied inclinations is crucial

Modernization of the electromagnetic vibration stand for testing aviation industry products

The article presents a methodology for modernizing a two-mass resonant electromagnetic vibration stand for testing parts of the aviation industry for vibration resistance. The main goal of the modernization is to provide a significantly lower disturbance force from electromagnetic vibration exciters to set the working body in motion. For this purpose, by introducing a third oscillating mass into the two-mass mechanical system, the interresonant mode of operation of the vibration stand is ensured. Analytical dependencies are presented that reveal the methodology for calculating inertial and stiffness parameters that ensure the transformation of a two-mass resonant vibration system into a three-mass interresonant vibration system. A specific example demonstrates the implementation of the proposed approach in the modernization of the design. The amplitude-frequency characteristics of the basic two-mass resonant and modernized three-mass interresonant vibration systems are constructed. It has been confirmed that to ensure the specified amplitude of oscillations of the working body in the modernized design, 4 times less disturbing force from electromagnetic vibration exciters (400 N) is required

Analysis on the influence of blade pitch angle on dynamic characteristics of the rotor system

At present, few studies focus on variable-pitch fans for small-to-medium turbofan engines, with most relying on hydraulic actuation that fails to meet strict environmental and efficiency demands. This paper analyzes an electrically actuated lead-screw servo-motor-driven variable-pitch fan rotor: at 1×10⁷ N/m support stiffness, the first critical speed exceeds the operational range and pitch angle’s influence is negligible, peak unbalance response is 1.22×10⁻⁶ m linearly decreasing with pitch angle, and vibration analysis avoids resonance. Results confirm the electric pitch-change concept’s feasibility

Coupling dynamics modeling and vibration characteristics analysis of TBM main drive system under complex tunnelling conditions

In order to ensure the reliable operation of TBM excavation process, it is particularly important to analyze the vibration characteristics in complex surrounding rock environments. The coupling dynamics model of the TBM main drive system proposed in this article considers the structural characteristics of distributed support and multi-source inputs, as well as nonlinear internal excitations such as bearing dynamic stiffness, gear meshing error, and tooth side clearance, which can more accurately calculate the dynamic characteristics of the main drive system. Based on the TBM scale test-bed, the modeling method and the vibration response of the main components were compared and verified. Based on the coupled dynamic model of the main driving system, the vibration characteristics of the driving system were analyzed under different excavation penetrations and different proportions of soft and hard surrounding rocks. The analysis results show that during the process of penetration from 5 mm to 6 mm, the average vibration increase speed is the highest, reaching 0.1493 g/mm. As the proportion of soft surrounding rock increases, the lateral unbalanced load and torque of the cutterhead significantly increase. Meanwhile, as the proportion of soft surrounding rock increases, the corresponding rate of load increase significantly increases. Within the range where the proportion of soft surrounding rock increases from 21 % to 35 %, its lateral overturning vibration RMS value increases by 13.08 %. Within the range where the proportion of soft surrounding rock increases from 35 % to 50 %, its lateral overturning vibration RMS value increases by 32.18 %. This can easily cause safety accidents such as the fracture of key load-bearing components of the system during the excavation process

Modeling of the transportation process on the Kokand-Andijan section of the Kokand regional railway track junction of the Uzbek railway

The article presents original research results on the substantiation of the forward motion parameters of a freight train with a fixed maximum mass of the train and the main traction and operational characteristics of the energy efficiency of O’z-EL type AC freight electric locomotives on a real flat section of the railway. Energy-optimal control modes for the movement of the aforementioned freight train by electric locomotives of the O’z-EL series have been developed using the original computer hardware and software complex KORTES, and their traction and energy characteristics are presented in the form of numerical values and graphs with an error of no more than five percent compared to the practical data of the Kokand locomotive depot of the Uzbek Railway. The above results will be further used by the authors to evaluate the effectiveness of various options for energy-optimal control modes for the power equipment of the Oʼz-EL series electric locomotives when implementing freight transportation on sections of the Uzbekistan railway industry of varying complexity under real operating conditions

Study on the influence of sewage pipeline construction on the foundation of the neighboring bridge

With rapid urbanization, conflicts between underground pipeline construction and existing bridge infrastructure have become increasingly prominent. This research aims to fill the gap in understanding the differential impact mechanisms and dynamic coupling effects between construction activities and bridge foundation stability. The study employs the finite element model to simulate the construction process, including working well excavation and pipe jacking, in a 120×80×30-meter three-dimensional model. Results show that both excavation and pipe jacking activities have minimal impact on the adjacent bridge foundations, with maximum horizontal displacements remaining within safe limits. This research provides a methodological framework for urban infrastructure risk assessment, offering technical references for balancing underground construction activities with existing structural protection

Correlation degree analysis of sliding bearing oil monitor data based on grey theory

Based on regular analysis of the spectrum, PQ value, precision moisture content and kinematic viscosity of a certain sliding bearing lubricating oil, this paper used grey theory to study the correlation degree within these four kinds of analysis indicators. It is hoped that it can achieve mutual verification and judgment of the state evaluation of sliding bearings. It can provides reliable basis for studying the internal operating rules of sliding bearings. It can also provide scientific basis for the management and maintenance of sliding bearings