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Purpose: Instantaneous unloading with equal force is usually used to simulate the sudden failure of cables. This simulation method with equivalent force requires obtaining the magnitude and direction of the force for the failed cable in the normal state. It is difficult, however, to determine the magnitude or direction of the equivalent force when the shape of the cable is complex (space curve). This model of equivalent force may be difficult to establish. Thus, a numerical simulation method, the instantaneous temperature rise method, was proposed to address the dynamic response caused by failures of the cables with complex structural form. Design/methodology/approach: This method can instantly reduce the cable force to zero through the instantaneous temperature rise process of the cable. Combined with theoretical formula and finite element model, the numerical calculation principle and two key parameters (temperature rise value and temperature rise time) of this method were detailed. The validity of this approach was verified by comparing it with equivalent force models. Two cable-net case with saddle curved surfaces were presented. Their static failure behaviors were compared with the dynamic failure behaviors calculated by this method. Findings: This simulation method can effectively address the structural dynamic response caused by cable failure and may be applied to all cable structures. Originality/value: An instantaneous temperature rise method (ITRM) is proposed and verified. Its calculation theory is detailed. Two key parameters, temperature rise value and temperature rise time, of this method are discussed and the corresponding reference values are recommended. [ABSTRACT FROM AUTHOR]

Utilities continuously observe cable failures on aged cables that have an unknown degraded basic insulation level (BIL). One of the root causes is the transient overvoltage (TOV) associated with circuit breaker reclosing. To solve this problem, researchers propose a series of controlled switching methods, most of which belong to deterministic control. However, in power systems, especially in distribution networks, the switching transient is buffeted by stochasticity. Since it is hard to model transient overvoltage due to its complexity, we propose a model-free stochastic control method for reclosers under the existence of uncertainty and noise. Concretely, to capture high-dimensional dynamics patterns, we formulate the recloser control problem by incorporating the temporal sequence reward mechanism into a deep Q-network (DQN). Meanwhile, we embed our physical understanding of the problem into the action probability allocation and develop an infeasible-action-space-elimination algorithm. Through PSCAD simulation, we first reveal the impact of load types on cables’ TOVs. Then, to reduce the training burden for the proposed reinforcement learning (RL) control method in different applications, we establish a post-learning knowledge transfer method. After the validation with our industrial partner, we exhibit several learning curves to show the enhanced performance. The learning efficiency is proved to be outstanding due to the proposed time sequence reward mechanism and infeasible action elimination method. Moreover, the results on knowledge transfer demonstrate the capability of method generalization. Finally, a comparison with conventional methods is conducted. It illustrates the proposed method is most effective in mitigating the TOV phenomenon among three methods. [ABSTRACT FROM AUTHOR]

Formation of dry zones around power cables is an important factor affecting the cable loading and may lead to cable failure. This phenomenon is ignored by some standards in the calculation of power cables capacity. Numerous efforts have been done by many researchers for cable monitoring. In this study, monitoring system based on measurements of temperature distribution surrounding the cable route is suggested. When reaching the temperature of the dry zone formation the system will produce a warning alarm. To the best of the authors knowledge, the invention of a device that gives a warning in the case of drying layers formation around the power cables has not received attention so far. The proposed device is characterised by cheap price, high accuracy and its simplicity in the design. The system is tested in the laboratory using different soil types. Field tests are done to verify the reliability of the device. [ABSTRACT FROM AUTHOR]

In this paper, we conducted studies on the relevant engineering parameters of submerged floating tunnel longitudinal structure, including plane alignment, tube stiffness, joint stiffness, cable stiffness, foundation settlement and cable failure, and carried out sensitivity analysis of some parameters. It is found that the plane curvature radius of submerged floating tunnel should take into account the deflection, bending moment and torsion of the tunnel tube and take values in combination with the code. The influence of tube stiffness and cable stiffness on tunnel system has a reciprocal relationship. The influence of joint stiffness is the same as that of tube stiffness. Offshore cable settlement and single vertical cable settlement are unfavorable settlement conditions. Deflection increment caused by mid-span cable failure is large. [ABSTRACT FROM AUTHOR]

Pretension is the pre-added axial tensile force on fully grouted bolt systems, which include rock bolts and cable bolts. Although a series of studies via lab testing and analytical modelling proved the importance of pretension in cable bolts, there is no systematic analysis to guide the optimal pretension values to be applied on cable bolts in different engineering geological conditions. Complicated geological conditions, such as anisotropic in-situ stress, bedding plane detachment and country rock deformation, cannot be fully represented in the lab or analytical work. In addition, field scale numerical models to investigate cable bolt performance and its interaction with various geological conditions are rare. This paper analyses the effect of pretension on the performance of cable bolts in underground coal mines via field scale numerical models, with considering different geological conditions (in-situ stress, bedding plane stiffness and rock mass properties). Numerical models were developed based on a case study mine in Australia with challenging ground conditions. The in-situ stress, properties of claystone and bedding planes are considered critical variables to be analysed. The results show higher pretension contributes to higher force along the cable bolt. Neutral points, where shear force in grout materials is zero, are used to describe the pretension-induced stress redistribution on cable bolts. Pretension also has a positive effect on roof and bedding plane management, resulting in a more stable roof condition. In addition, high pretension and high in-situ stress are more likely to result in cable-grout (CG) interface failure since the relative vertical displacement difference between cable bolts and the surrounding rock mass is higher. Once CG interface failure is generated, the pretension effect turns out to be negative, leading to severe roof sagging and bedding plane aperture. This paper provides a guide to the application of pretension in coal mining. • Developed a numerical model to illustrate the effect of pretension on cable bolts. • Analysed effects of pretension and cable-grout (CG) interface failure on cable bolts. • Investigated the relationship between pretension applied and CG interface failure generated along cable bolts. • CG interface failure induced by excessive pretension is more sensitive to bedding plane properties. [ABSTRACT FROM AUTHOR]

Ice accretion on power transmission lines is one of the major causes for cable failure in Zhaotong area, Yunnan Province, South China. This study proposes a method to predict the remaining‐dangerous time (RDT) of the icing load accretion on an interval of the power transmission lines with modified hidden semi‐Markov model (HSMM). Based on the predicted RDT of the cables during ice accretion, the appropriate preventative measures can be scheduled in advance by electric power companies. The estimation model with the learning algorithm of support vector machine for icing load accretion is built through historical icing load accretion data and meteorological conditions first. Then, the estimated icing load accretion sequence can be obtained through the estimation model by forecasting the meteorological conditions. The modified HSMM method can eliminate the possible underflow issue during computation, and be used to build the RDT prognosis model. With the estimated icing load accretion sequence and RDT prognosis model, the authors can predict RDT of the icing load accretion on an interval of the power transmission lines. The developed prognosis algorithm is verified through collected meteorological conditions and icing load accretion data on the Dazheng 73# power transmission line in Zhaotong area, Yunnan Province, South China. [ABSTRACT FROM AUTHOR]