Cable imperfections

The interface between conductor shield and insulation is the region of the highest stress in the cable insulation stmcture. Any imperfections at this interface, especially sharp protmsions of the conductor shield into the insulation, will cause high local electrical stress that may reduce the dielectric strength of finished cable. Calculation of the stress enhancement, for a 15 kV cable with a 4.4 mm (175 mil) insulation thickness, indicates that the common round 50 p.m (2 mil) radius protmsions increase the electrical stress by a factor of 30 and a sharp 5 fim protmsion will increase the electric stress by as much as 210 times (11,20). 

The current is carried to the electrolyzer by copper or alluminium busbars from which it is distributed by cables or by a system of elastic copper lamellae to the terminals of the electrodes. The current passes through many points of contact which determine the magnitude of so called contact resistance. The more imperfect are the contacts at these points the greater the losses in electrical... 

Factors other than the stress induced ageing also play an important role in cable failure. Thorough investigation (7, 8) has revealed that imperfections present in the cable are responsible for premature failures and also indirectly for the gradual deterioration. 

Imperfections. A schematic view of the potential imperfections (Figure 4) depicts those occurring in the freshly prepared cable. Others that may develop during the service life will be discussed later. 

There are two major sources of stray capacitance. First, the capacitance of the po-tentiostat and leads. By using high-quality cable of minimum length, for example, by mounting the current-to-voltage converter directly over the electrochemical cell, and by avoiding the use of switches as far as possible, stray capacitance from the electrochemical system can be minimized. Second, the microelectrode itself. For example, if there is a small imperfection in the seal between the insulator and the electrode material, then solution leakage will cause the RC cell time constant to increase massively and the Faradaic response may... 

One of the most demanding applications for conducting compounds is as a layer around the center condnctor of a high voltage cable. The purpose of the compoimd is to smooth any snrface imperfection that wonld otherwise resnlt in high electric field gradients and the breakdown of the insnlating layers. These... 

Notwithstanding the many advantages of screw presses, they still have some important imperfections and that is why hydraulic lead cable sheathing presses continue to find a wide application. 

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