CABLE Subject

Alloy B Pb-0.8-0.95Sb 9.6 Solid type cables and telecommunication cables subjected to severe vibrations... 

Alloy 1/2C Pb-0.18-0.22% Sb-0.06-0.09 Cd 4.2 0.07% Oil-filled and submarine power cables. Power cables subjected to severe vibrations in service. Acceptable for most types of reinforced cables... 

Cu-Te Pb-0.06Cu-0.045Te 6.9 Cables subjected to high vibrations and oil-filled cables... 

F3 Pb-0.15 As-0.15 Sn-0.1% Bi 6.1 PILC cables, submarine cables, power cables subjected to severe bending or vibration conditions... 

Cables subject to frequent movement, such as those used to supply mobile cranes, should be flexible to BS 6708. This standard calls for a protective conductor other than the armour and for circulating current earth monitoring to prove its integrity (see Fig. 3.1). Cables in the llOV system are usually unarmoured plastics-insulated and plastics-sheathed. The safety... 

This type of structural behavior is called geometrically nonlinear and invalidates the use of the principle of superposition, thus of aU commOTily used stmctural analysis methods. The so-called nmiltnear analysis methods are required, often involving iterations to achieve cmivergence, as equilibrium equations must now be formulated in the deformed geometry, which however is unknown. Thus, nonlinear analysis is a lot more time and computationally demanding than linear ones. Typical examples of structures that are prone to geometric nonlinearity are cables subjected to transverse loads, shallow arches and domes, slender bars that buckle under axial compression, and thin-walled shells (Fig. 7). 

The insulation on the conductor is therefore exposed to a considerable concentration of o2one and subjected to chemical reactions and mechanical erosion from the impingement of ions. This causes deleterious effects and shortens the life of the cable. 

There are several methods to determine and compare the resistance to partial discharges. Some tests are done on finished cables, such as the U-bend test, and others are done on laboratory samples molded from the insulation, that are subjected to partial discharges created by sharp objects, such as needles under high voltages. The tests compare either the energy required or the length of time required to erode or fail (short circuit) samples of similar thickness. 

Underwriters Laboratories, Spec. Subject 15 for Power-limited Circuit Cable Class 2, (NEC article 725), Melville, N.Y. 

The first few turns of the line end coil of a motor or transformer and short lengths of interconnecting cables and overhead lines and their associated terminal equipment, will thus be subject to severe stresses and will be rendered vulnerable to damage by such sleep-fronted transient voltages. 

The terminal equipment connected on the secondary side of the transformer is thus automatically protected as it is subject to much less and attenuated severity of the transferred surges than the secondary windings of the transformer. Nevertheless, the BIL of the interconnec-ting cables and the terminal equipment must be properly coordinated with the BIL of the transformer secondary, particularly for larger installations, say, 50 MVA and above, to be absolutely safe. Example 18,2 will explain the procedure. 

In an attempt to provide as much information on the related subjects as possible and to make the book more complete for a project or a design engineer w e have provided data and tables on cables and described in detail the procedure for the selection of the type and size of control and LT and HT pow er cables. 

The switching-off method for 7/ -free potential measurement is, according to the data in Fig. 3-5, subject to error with lead-sheathed cables. For a rough survey, measurements of potential can be used to set up and control the cathodic protection. This means that no information can be gathered on the complete corrosion protection, but only on the protection current entry and the elimination of cell activity from contacts with foreign cathodic structures. The reverse switching method in Section 3.3.1 can be used to obtain an accurate potential measurement. Rest and protection potentials for buried cables are listed in Table 13-1 as an appendix to Section 2.4. The protection potential region lies within U[[Pg.326]

Further chapters cover in detail the characteristics and applications of galvanic anodes and of cathodic protection rectifiers, including specialized instruments for stray current protection and impressed current anodes. The fields of application discussed are buried pipelines storage tanks tank farms telephone, power and gas-pressurized cables ships harbor installations and the internal protection of water tanks and industrial plants. A separate chapter deals with the problems of high-tension effects on pipelines and cables. A study of costs and economic factors concludes the discussion. The appendix contains those tables and mathematical derivations which appeared appropriate for practical purposes and for rounding off the subject. 

The market for PPVC film and sheet is only slightly less than for wire and cable insulation. Uses are as diverse as seepage barriers, factory doors, inflatables, baby pants, car trim, covering materials for book bindings and document cases and shower curtains. UPVC film has also been widely used for packaging of food, particularly for shrink-wrap purposes, but this market has been subject to some substitution by polypropylene. 

Many materials are subject to deterioration by ultraviolet light (UV). particularly many of the plastics and fiberglass materials. Fiberglass materials for outside use should be specified as UV-stabilized, and most plastics installed outdoors should be carbon-impregnated (black in color). It is particularly recommended that plastic cable ties, which secure cables in cable trays, be carbon-impregnated if installed outdoors. 

The cathodically protected primary structures may be the hulls of ships, jetties, pipes, etc. immersed in water, or pipes, cables, tanks, etc. buried in the soil. The nearby unprotected secondary structures subjected to interaction may be the hulls of adjacent ships, unbonded parts of a ship s hull such as the propeller blades, or pipes and cables laid close to the primary structure or to the cathodic-protection anode system or groundbed. 

Melt filtration systems are commonly employed in pigment master-batch production and in situations where the presence of defects in the compound may have a critical effect on its subsequent processing or properties. This is vitally important, for example, in fibre-spinning operations involving extrusion of polyester or polyamide through fine spinneret plates [162], and in minimizing breakdown of polymer cable insulation subjected to electrical stress [163]. 

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