This paper considers electric shock hazard due to induced sheath voltages in 110 kV power cables. The purpose of this paper is to find an optimal configuration of the power cable system, taking into account electric shock hazard and ability of the system to transfer maximal power. A computer simulations on a computer model of the local power system, comprising high voltage power cables, were carried out. This model enables to analyse various configurations of the metallic cable sheaths bonding and earthing (singlepoint bonding, both-ends bonding, cross-bonding) and their impact on induced voltages in the cable sheaths. The analysis presented in the paper shows, that it is possible to find an optimal configuration of the complicated power cable system, in terms of electric shock hazard, maximal power transfer as well as economic aspects.
Flexible, slender structures like cables, hoses or wires can be described by the geometrically exact Cosserat rod theory. Due to their complex multilayer structure, consisting of various materials, viscoplastic behavior has to be expected for cables under load. Classical experiments like uniaxial tension, torsion or three-point bending already show that the behavior of e.g. electric cables is viscoplastic. A suitable constitutive law for the observed load case is crucial for a realistic simulation of the deformation of a component. Consequently, this contribution aims at a viscoplastic constitutive law formulated in the terms of sectional quantities of Cosserat rods. Since the loading of cables in applications is in most cases not represented by these mostly uniaxial classical experiments, but rather multiaxial, new experiments for cables have to be designed. They have to illustrate viscoplastic effects, enable access to (viscoplastic) material parameters and account for coupling effects between different deformation modes. This work focuses on the design of such experiments.
By simulating the actual working conditions of a cable, the temperature variation rule of different measuring points under different load currents was analyzed. On this basis, a three-dimensional finite element model (FEM) was established, and the difference and influence factors between the simulation temperature and the experimental measured value were discussed, then the influence of thermal conductivity on the operating temperature of the conductor layer was studied. Finally, combined with the steady-state thermal conductivity model and the experimental measured data, the relation between thermal conductivity and load current was obtained.
The paper analyses the possibilities of treating the ignition cable in the internal combustion engine as a distributed parameter system. It presents the experimental verification of computer simulations of signal propagation generated by ignition systems in the ignition cables, modelled by the distributed parameter system. The tests conducted to determine the wave parameters of ignition cables, as well as the results of numerical simulations and their experimental verifications, are presented. It is concluded that the modelling of the ignition cable by means of a long line gives positive results that can be used for the design of a spark plug with impedance equal to wave impedance of the ignition cable.
Tensile structures in general, achieve their load-carrying capability only after the process of initial form-finding. From the mechanical point of view, this process can be considered as a problem in statics. As cable systems are close siblings of trusses (cables, however, can carry tensile forces only), in our study we refer to equilibrium equation similar to those known from the theory of the latter. In particular, the paper regards designing pre-tensioned cable systems, with a goal to make them kinematically stable and such that the weight of so designed system is lowest possible. Unlike in typical topology optimization problems, our goal is not to optimize the structural layout against a particular applied load. However, our method uses much the same pattern. First, we formulate the variational problem of form-finding and next we describe the corresponding iterative numerical procedure for determining the optimum location of nodes of the cable system mesh. We base our study on the concept of force density which is a ratio of an axial force in cable segment to its length.
The article presents the assumptions, characteristics and description of the implementation of a pilot system for on-line monitoring of partial discharges in heads of the high-voltage cable lines. The main purpose of the implementation was to increase the reliability of cable line heads by equipping them with a system of continuous assessment of technical condition with direct transmission of measurement data and alarms to the SCADA system. In order to achieve the assumed goal, unconventional methods for measuring partial discharges were used, the application of which does not require disconnecting the line from the voltage. The implementation was carried out on an active 110 kV high voltage cable line in the area of activity of one of the Distribution System Operators.
The hereby paper discusses the influence of cable length on the SHM systems with the use of vibrating wire dynamic measurements. Vibrating wire sensors are mainly used for measuring stable or slowly changing strains, e.g. system installed on Rędziński Bridge in Wroclaw. From some time applications of these sensors for measuring dynamic deformations are becoming popular. Such tests were conducted on STS Fryderyk Chopin. New solutions generate new problems. In this case: the operational stability of systems exciting wire vibrations. The structure of such sensors and the electric cables length has an essential influence on their operations, what is undertaken in the paper. The subject of investigations constitutes the measuring system based on self-exciting impulse exciter, for which impedance parameters of electric cables and of the vibrating wire sensor were the most essential. The mathematical model of the system, experimental verification of the model as well as the results of theoretical analyses at the application of electric cables of various lengths are presented in the paper.