Chapter 14 Cable Support Systems - Sourceiex

Session 14 – Cable Support Systems

Cable Support Systems in theInternational WorldIEC61537‐2004If full details of the cabling layout are available then the likely cable load can be calculated usingeither manufacturer's published information or the tables of Cable Weights and Diameters whichare given below. However it is often necessary to select a tray or ladder design in the absence ofaccurate information on the likely cable load. To assist this selection process a useful approachcan be to choose a likely size of tray or ladder and then to estimate the maximum cable weightwhich is capable of being contained within it. This estimate may be arrived at using the followingguide:‐Max. cabling capacity (kg/m) Cable laying area (m2) x 2800

International Cable Support Standards &How they compare vs. NEC/NEMARequirements and standards

International Cable Support Standards &How they compare vs. NEC/NEMARequirements and standards

Support Load CalculationPer IEC 61537Even spread load and point weightsAll load tests are done with evenly distributed load. To be able to calculate from an evenlydistributed load to a point load this formula is used2 X Point LoadEvenly Distributed Load Support DistanceWhen using this formula point loadscan be counted for and used as designbasis. Even if thisequation takes into account that thepoint load is placed on worst part ofthe span, i.e. the midpoint, it should always be a goal toplace the equipment as close to thesupports as possible.

Support Load CalculationPer IEC 61537One or more spans (IEC 61537 7.3i)For installations with more than one span it is important to notice that the loadingcapacity is not the same form one end to the other. The middle span will be able tohandle more load than the two spans on the end. It can therefore be necessary toreduce the distance between the supports for the end spans. For some of theinstallations the end span will have less load to carry than the mid spans, however ifthe load is evenly distributed from one end to the other the support distance have tobe reduced with ¼ on both ends. The load capacity is reduced a great deal by settingup just one single span.For all the tests according to IEC61537 both the mid span and the end span are tested in termsof safe working load and deflection. For those cases where splice connectors have been usedon the end span, it’s been placed ¼ from the support point, i.e. the most favourable position.

Support Load CalculationPer IEC 61537DeflectionDeflection will vary over the spans. The mid span will have less deflection than the endspans and the single spans. Deflection tests according to IEC 61537 have been carriedout. The tests are done on single spans, i.e. “a worst case” approach. According to thestandard the deflection must not be more than 1:100, i.e. that deflection for example ona span on 3 meters can’t be more than 3 cm.Placing of splice connector (IEC 61537 7.3j)In reality it is hard to plan the locations ofthe splice connectors, but it is howeverimportant to be aware of this. The leastbeneficial location for the splice connectorsare at the mid point of the span or right overthe support. Placing the splice connector inthese two places should be avoided,especially on end spans. If possible, it ispreferred to put the splice connectors ¼ ofthe span length from the support.

Expansion Splice PlatesRecommended UsesCalculations : Installing Expansion CouplersTemperature dataMinimum temperature at siteMaximum temperature at siteTemperature when installing cable laddersCalculationsTemperature differentialExpansion of stainless steel for this temperature rangeExpansion coupler gap when installing (Including safety factor)Minimum distance between expansion couplersConstantsExpansion of steel per increased ºC:Oglaend expansion coupler allows movement ofFill in valuesin grey cells-152520ºCºCºCExample of installationin warm weatherCalculate400.6915.058ºCmm/mmmm0.0173 mm/m40mmThe gap between the couples when installing 15 mmExample of installationin cold weather

Cable separation within cablemanagement systems

Cable Tray WiringMore use of protection by location than is typical in US installations. The useof basket tray is typical for light weight last meter cable runs in onshoreapplications. The use of ventilated cable tray is common for heavier weightcables and offers more protection in offshore applications.Cable ladder is typically used in feeder applications for longer runs of multiplecables or of higher ampacity and weight.

Cable Support Systems in theInternational WorldTypical Cable Weight Information PVC Unarmored StrandedCopper Power Cables to BS6346Nom.Area ofConductor, mm22 core3 core4 .013.262.54008.553.212.661.416.769.6

Cable Support Systems in theInternational WorldSupport of cable tray and ladder is typically done in the same fashion as US installationsbut generally has fewer restrictions as to loading design. Calculations for loading ofcable into tray is based upon manufacturers cable data compared to loading data fortray manufacturer.

Cable Support Systems in theInternational WorldIt is not uncommon to use either the cable trayor ladder to be used as a means to directlymount lighting fixtures to the support structure.Special bracketry is designed for various brandsof products to be supported in this fashion.Examples of these types of installations areshown here .Stretch preventors are typically used to relievestrain on the cable as the enter light fittings.

Cable Support Systems in theInternational World ‐ Typical

Cable Support Systems in theInternational World ‐ Typical

Cable Support Systems in theInternational World ‐ Typical

Cable Support Systems in theInternational World ‐ Typical

Cable Support Systems in theInternational World ‐ Typical

Cable Support Systems in theInternational World ‐ Typical

Cable Support Systems in theInternational World ‐ Typical

Cable Support Systems in theInternational World ‐ Typical

Support Systems InstallationExamples

Support Systems InstallationExamples

Support Systems InstallationExamples

Support Systems InstallationExamples

Cable Cleats Trefoils for SingleCore CablesPower cables under short‐circuit conditions (especially three‐phase, single conductor cable arrangements) are subject tosignificant forces as a result of induced magnetic fields. Forthree‐phase, single conductor cables, these forces cause violentthrashing of the individual conductors, frequently resulting ininadequately supported cables jumping out of their cable trayor raceway systems. Such unrestrained cable movement cancause cable damage, damage to surrounding equipment andpossible injury.A European Standard now exists – EN 50368:2003, CableCleats for Electrical Installations. This Standard wasapproved by CENELEC (the European Committee forElectrotechnical Standardization) in September 2003 andpublished in October 2003. EN 50368:2003 has the statusof an approved British Standard.

Cable Cleats Trefoils for SingleCore CablesGood engineering practice for the use of single core cables without theuse of conduit systems is to use cable cleats to minimize downtime andpotential dramatic destruction of the cable systems and surroundingenvironment

Cable Cleats Trefoils for SingleCore Cables

Cable Cleats Trefoils for SingleCore Cables

Typical Installation of single core cable

Per IEC 61537 Deflection Deflection will vary over the spans. The mid span will have less deflection than the end spans and the single spans. Deflection tests according to IEC 61537 have been carried out. The tests are done on single spans, i.e. “a worst case” approach. According to the