Cable installation methods

In principle, material selection, cable design, and installation method can work together to produce the solution for meeting performance requirements within standards. However, in many cases the standards have evolved based upon certain materials and constructions, thus limiting material selection options unless one is willing to propose changes to standards, which is a lengthy proposition. 

Centralized methods of sensor networking make impractical demands on cable installations and network bandwidth. The burden on commnnication system components, networks, and human resources can be drastically rednced if raw data are processed at the source and the decisions conveyed. The same holds true for systems with relatively thin communications pipes between a source and the end network or systems with large numbers of devices. The physical world generates an nnlimited quantity of data that can be observed, monitored, and controlled, bnt wireless telecommunications infrastructure are finite. Thus, even as mobile broadband services become available, processing of... 

Individual conductors may be installed in trunking or conduit and individual cables may be clipped directly to a surface or laid on a tray using the wiring system which is most appropriate for the particular installation. The installation method chosen will depend upon the contract specification, the fabric of the building and the type of installation - domestic, commercial or industrial. 

Protection of cables in walls - section 522 has been rearranged and modified to make it clearer. Amendment 3 at 522.6.202 states that all installations buried at a depth of 50mm or less, which includes cables installed in partitions constructed of metal parts irrespective of depth, shall have 30 mA RCD protection, unless other methods detailed in 522.6.203 have been applied. Compatibility - Regulation 512.1.5 tells us that the installation designer must ensure that all the installed fixed equipment is designed and manufactured in accordance with the Electromagnetic Compatibility (EMC) Directive. Installations composed only of CE marked apparatus will conform to this directive. 

An EC funded project has been examining the various test methods that are used to evaluate electric cables and their fire performance. This was funded by DG XII of the Commission and is designated as Fire Performance of Electric Cables (FIPEC). Various levels of testing have emerged from the project ranging from a small-scale, cone ealorimeter test procedure especially developed for cables and their constituent materials, a full scale proeedure based on lEC 60332-3, but utilising heat rate release and smoke production rate (SPR) measurements, and a real scale test for mock cable installations. 

For each environment there may be numerous other specific considerations that are germane to a particular application, such as sewer or shipboard environments, or to an installation method, such as aerial self-supporting or jetting into miniature ducts. As with the optical fibers there are a number of unique cable designs optimized for various combinations of application and installation method. The performance criteria for the most common designs are also specified by the various telecommunications industry forums, which will be discussed at the end of this section. 

There are a number of diverse installation methods for the various spaces in which fiber optic cable is used. The installation methods discussed below are primarily associated with outside plant applications but may also have some uses in other environments. The relatively benign environment of the inside plant means that installation considerations are somewhat less critical, although this is not to say that they are not important. 

Combining the various attributes discussed to this point enables the construction of a wide range of cable types for various applications. The most common cable designs are described later on and the design of choice for a particular application depends on a number of factors. The primary considerations are fiber count, installation method, and the environment. Specific designs based on the basic constructions discussed (i.e., stranded loose-tube, central tube, and tight buffered), but which are specialized for a particular application, are discussed in Section 9.2.4. 

Installation methods and handling procedures for cables to protect conductors from physical damage... 

The running of telephone lines through power lines is long discontinued. They are now run on separate structures within a city and nearby areas at audio frequency (— 0.3-3.4 kHz), and maintain enough distance from HT power distribution lines. They are therefore almost unaffected from such disturbances. Nevertheless, interferences must be kept in mind when installing these lines so that they are out of the inductive interference zone of the power lines. The latest method in the field of communications to avoid disturbances is to use underground optical fibre cables, where possible, as discussed later. Optical fibre cables are totally immune to such disturbances. 

Figure 11 -7 shows the basic circuit diagram for a tank with two domes. The protection current flows via the two interconnected openers of the cover grounding switch to the cathode connection. If one of the covers is opened, the protection current circuit is broken and the tank grounded via the closing contact. The unconnected cable connection of the tank is without current and can be used for measuring potential. By this method, only one tank at a time is separated from the protection system while the other parts of the installations are still supplied with protection current. 

Direct current installations that are grounded in several places cause stray currents in the soil which can interfere with other installations (see Section 9.2). All dc railways are sources of stray currents. Protection methods that can be applied in the same way to cables are described in Chapter 15. 

In some instances, it is required to measure the sum of the energy supplied along several feeders. This is the case, for example, when a factory site is fed by more than one cable and the tariff is based on the overall energy and maximum demand used. The usual method of doing this is to summate the currents in the individual feeders by installing separate current transformers in each and connecting their secondaries in parallel (Figure 17.3). 

A number of methods may be used to reduce the interaction on neighbouring structures. In some circumstances it may be practicable to reduce the current output applied to the protected structure or to resite the ground-bed so that the anode effect on an unprotected pipe or cable is altered as required. The physical separation between the groundbed and nearby buried structures can be increased by installing anodes at the bottom of deep-driven shafts and substantial improvements can be made using this technique. 

The speed of information transfer can be increased by switching from twisted pair cables to coaxial or fiber optics, however, these types of cables add to the installation costs. In the future, communications between sensors and multiplex boxes and the rest of the system may use a combination of technologies including traditional means such as twisted wire and coaxial and non-traditional methods such as infrared or radio wave. 

Heat shrink sheets are used for many of fhe same applications as heavy wall shrink tubing. The advantage of the sheet over a tube is that it can be conveniently slipped over the area to be protected, for example, over continuously installed cable. There are many methods to close the heat-shrinkable sheets, such as zippers, rail and channel, heat-sealable bonds, etc., some of them patented. ... 

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