Cables selection

Nearly all polymeric materials require the addition of antioxidants to retain physical properties and to ensure an adequate service life. The selection of an antioxidant or system of antioxidants is dependent upon the polymer and the anticipated end use. A product that will not be exposed to the elements for a long period of time such as polyethylene grocery bags does not need a long term stabilizer polyethylenes used to iasulate communication cable must be stabilized for many years of service. 

The fact that the polymer contains no halogens along with certain unique compounding techniques for flame resistance prompts the selection of ethylene—acryflc as jacketing material on certain transportation/mifltary electrical cables and in floor tiles. 

Table 12.4 Selection table for switches, fuses, relays and cables for different sizes of LT motors...

In some cases, where the nearest rating of the fuse itself is too high for the rated current, a larger cable is recommended. The thermal (/ - t) characteristics of all such components will vary from one manufacturer to another and may not be readily available with a design or a field engineer, while making the selection. The manufacturers of such components therefore as standard practice, perform this coordination for their products and make such data readily available for the user lo make a quick selection. It may be noted that OCR and fuses at least, of different brands, will require a new coordination. 

To increase the impedance of the network, a series resistor or reactor is sometimes used to contain the fault level of a system within a desirable limit. This may be required to make the selection of the interrupting device easy, and from the available range, without an extra cost for a new design as well as an economical selection of the interconnecting conductors and cables. Such a situation may arise on HV >66 kV or EFIV > 132. kV transmission networks, when they are being fed by two or more power sources, which may raise the fault level of the system to an unacceptable level. The cost of the interrupting device for such a fault level may become disproportionately high, and sometimes even pose a problem in availability. 

The ratings and sizes of main components and cables can be selected from manufacturers catalogues. But cables required for the switchgear internal control and power wirings, being typical of all, are normally identified by their cross-sectional area rather than the current ratings. We have therefore piovided the technical data and current ratings for the most common sizes of such cables for a ready reference in Table 13.15. 

Appendix 1 Selection of Power cables 16/531 A 16.1 Introduction 16/531 A16.2 Technical details 16/544 A16.3 Service conditions 16/544 A 16.4 Recommended derating factors 16/544 A 16.5 Voltage drop 16/544... 

To provide a reference for those working on power projects or at sites, we provide some important data on different types of LT and HT power cables in this appendix. The cables described here are in use for all kinds of power distribution applications. Of these, XLPE cables are also used for power transmission applictiiions. To help a user to select the most appropriate types of cables, we also provide a brief comparative chart of the various types of cables being manufactured. Tables giving the technical particulars of such cables in all voltage ratings have also been provided. 

The selection process of power cables is almost the same as that of a bus system discussed in Section 28.3. For simplicity we consider only the basic data for selection which would suffice the majority of applications. For accurate calculations a similar approach will be essential as for the bus systems (Chapter 28). For site conditions and laying arrangements which may influence the basic rating of a cable, corresponding derating factors have also been provided. The information covered here will be useful to users to meet their cable requirements, although the data may vary marginally for different manufacturers. For more data on cables, not covered here, reference may be made to the cable manufacturers. 

It is possible that at certain installations, even after selecting the size of the cables on the basis of the site conditions and the laying parameters as discussed above, a larger cable may become imperative as a consequence of a higher voltage drop. 

Consider a 55 kW motor to be switched direct on-line and instalied, say, at 75 m from its controlgear. To select the most appropriate cable size refer to Table 12.4, where... 

Figure A16.4 Current - time characteristics for aluminium cables for the selection of minimum cable size for a given fault level...

Lower kVA demand will reduce the load current (due to reduced / P losses) and result in an economical selection of switchgear components and cables. 

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 protection current produced by the usual full-wave rectifier has a 100-Hz alternating component of 48%. There are receivers with selective transmission filters for 100 Hz, which corresponds to the first harmonic of the cathodic protection currents [45]. With such a low-frequency test current, an inductive coupling with neighboring pipelines and cables is avoided, which leads to more exact defect location. 

The motor cost is but one facet of any cost study for selecting voluigc level. The study must compare installed cost of motor, starting equipment, transformers, and power and control cables at the various levels under consideration, as well as plant standards. 

MG 2 Safety Standard for Construction and Guide for Selection, Installation, and Use of Electric Motors and Generators MG 10 Energy Guide for Selection and Use of Polyphase Motors VE 1 Cable Tray Systems... 

This is a letter report from JBF Associates Inc., to Sandia National Laboratories (SNL) summarizing JBF s efforts to analyze dependent (common cause) failures and failures caused by harsh environments. The information used for the analysis was ta)cen from over 1000 failure reports (mostly abstracts of LERs that were assembled for other studies). The 26 groups of components selected for study are accumulators, batteries, cables, control rod drives,... 

When located at the motor the capacitor bank will be normally cabled from the motor terminal box, so that the size of the motor cable can then be selected on the basis of the reduced-power factor corrected current drawn by... 

The cable must be selected on the basis of full-load current rating, voltage drop on both running and start-up, and short-time current rating. 

In selecting a cable for a particular installation, the following factors need to be considered ... 

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