EoW September 2007

english

Advanced Mechanical Protection Using Polymeric Armour By Paul Cinquemani, Bill Wolfe, Carroll Lindler, Paolo Veggetti and Marco Frigerio, Prysmian Power Cables & Systems USA

Abstract Electric power and control cables can be subjected to very high tension during installation. As cables are pulled around bends sidewall bearing pressure (SWBP) should be monitored to keep it below the limits set by industry standards and manufacturer’s recommendations, otherwise the cable can get damaged. cable installers have used various ways to protect cables from high sidewall bearing pressures. Cable manufacturers use metal clad armour of either aluminium inter- locked armour (AIA) or continuously corrugated metal armour. Cable installers have several options. They can increase the bending radius the cable is pulled around or can design to install shorter cable pulls and splicing the several sections. This paper will detail the development and evaluation of a new design of power cable that provides increased mechanical protection without the use of metallic armour while also improving overall flexibility. The new design incorporates a polymer layer that has been shown to improve both the mechanical toughness of electrical power cables while providing improved flexibility compared to cables using metallic armour. that polymeric armour provides five times better impact performance than metallic armoured products. Power cables that contain polymeric armour can achieve up to 3,000 pounds/radius foot of SWBP. This allows installers and customers to install cables for longer distances without the need for expensive splices which also affects cable reliability. Typically, manufacturers and The data presented support

Figure 1 : Conventional type MC – continuous corrugated aluminium sheath design ▲

Figure 2 : Polymeric armour design

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1. Introduction The NFPA National Electrical Code (NEC) clearly defines the applications where metal clad cables (Type MC) are required to be installed or may optionally be used in the occupancies covered therein [1] . The specific types and requirements for such

metal clad cables are also clearly defined in UL Standards 1569 and 1072 [2] [3] [4] . In many other locations and applications, metal clad cable may be used as a beneficial option, ie conduit replacement or as an alternate design when greater mechanical abuse resistant cable is desired by the end user.

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EuroWire – September 2007