Truck Trolley System

7/27/2019 Truck Trolley System

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Open-cast mining is the classic field ofoperation for diesel powered trucks. Butrising fuel prices and greater environ-mental awareness often lead to problems- both economic and ecological. Theseproblems are solved convincingly by theSiemens Truck Trolley Sy'stem which chan-nels electric power to relieve the dieseldrives, for example on steep ramps in themine. Truck trolleys are powerful, energy-efficient and flexible.

Featu res

. Decreased operatinq costs due toreduced energy and diesel enginemaintenance costs. lncreased productivity due to increasedtruck speed on the ramps resulting in areduced time cycle. Reduced maintenance due to anincreased service interval and reducedwear on diesel engines. Environmental benefits due to fuelsavings up to 30 %

Contact wire working height upto9m'Y?yr'::'::l piof:le: lelsht:'jp lo 1s msteel 110t11e, l:"nln 'o l: 'l In2]:o:lact wlre 1 :, *":r-:nsur wy1e, each 1 50 mm22x contact wire + 2x messenger wire, each 150 mm'z150 mm2i ""''ll: ::l'l"f i :s :qI f 1_:::up to 1,500 m (2x 750 m).

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Switchgear housing hermetically sealed containerAll equipment is skid mounted to facilitate transport and re{ocation within the mine.Rated power and voltage to be determined depending on electrical requirements of trucksand operating conditions.


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System OverviewThe extreme conditions under which dump trucks have tooperate around the clock in the mines pose high demandson operational reliability. Rough terrain with constantlychanging mining roads, deficient infrastructure and highgross vehicle weights call for a reliable and flexible powersupply system.A trolley assist package co-developed by Siemens tosupplement diesel-electric drives, the Truck Trolley Systemhas established a fi ne track record in open-cast mines in anumber of countries. This system enables the truck tooperate on low-cost electricity.The modular design of the individual system componentsfacilitates the conversion of existing diesel trucks.An existing fleet of trucks can be converted with minimumeffort thanks to a modular design incorporating field-provenstandard components.High flexibility is the hallmark of this logically -structuredsystem - a feature which ensures easy adaption of thesystem to any customer requirements. lndividual aspects ofa mine's operation and the existing infrastructure can bechanneled into the system during the design phase.Standard components ensure not only cost efficient stockingof spare parts but also immediate removal of any faults thatoccur. The entire Truck Trolley System can be expanded,dismantled or moved without any difficulty, even after manyyears of operation.

The power supply via overhead contact lines increases thespeed of the trucks, especially on gradients. With thestandard motors available today, it is possible with this systemto attain signifi cantly higher operating speeds, which alsomeans quicker turn-around times for the trucks and thereforeincreased haulage.Previous experience has shown that the Truck Trolley Systemis a real economical and technical alternative, even inaround-the-clock mining operations. The alternating supplyof power from the diesel unit to the overhead contact lineresults in fuel savings of approximately 30 0/0. The electricitysupplied through the catenary system is generated at lowercost and with minimal environmental impact.The design of the heavy-duty dump trucks is based on adiesel-electric plant which powers the wheel hub motors ofthe rear axles.To permit truck trolley operation. the vehicle is equipped witha conversion package i,vhich comprises a control unit withelectric and electronic components, two pantographs withcorresponding support frame, and the necessary cabling. Thecompletely preassembled control unit is mounted in a cubicle.Carbon strips establish the contact between the pantographsand the overhead contact wires and ensure optimum currentcollection with minimum contact wire wear.The power necessary for electric operation is supplied viaoverhead contact lines. The vehicle changes over fromdiesel-electric pperation to full electric drive as soon as theraised pantographs make contact with the catenaries. Thismodal changeover occurs automatically when the controlsystem installed in the dump truck detects the specifiedparameters such as contact wire voltage and minimum speedof the truck.The Truck Trolley System is most economical on the ramps,where most of the total energy is consumed. Therefore, thetrolley is normally installed on the uphill stretch where thebenefits of fuel savings and increased speed are greatest.The drawing shows the normal case, the trucks drive up theramp with a high gradient from the loading point to the placewhere they dump the load. Then they drive down the samegradient or ramp empty.

$irnplifi ed exarnple of truck operation with theTruck Trolley System


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Truck ConversionThe illustration shows the additional equipment necessaryfor trolley assisted operation. Two pantographs aremounted parallel to the front of the truck, so that electricpower can be collected from over-head lines. Additionalcontrol devices are added to the truck, so that power fromthe overhead contact lines can be transmitted correctly tothe wheel motors.When the truck is connected to the trolley line, the dieselengine and alternator are not used for propulsion. Theengine automatically drops to idling speed, with all thepower for propulsion coming from the overhead lines. Thesystem is designed to provide the highest possible linevoltage which the drive and motors can safely handle, sothat the truck will operate at the highest possible speed.The speed of a diesel-powered truck is limited by its enginehorsepower, but the speed of a trolley truck is only limitedby the line volt-age and the capabilities of its drive tractionmotors.Pantmg ra ph Senssr $ys{,mmlThe Pantograph Sensor System ensures safe and reliableoperation of the trucks under the contact wire and ensuresthere is no risk of damage to the overhead contact line. Adisplay panel installed in the driver's cabin assists thedriver in keeping the correct position under the contactwire.The Pantograph Sensor System consists of sensor strips, abox for electronic components and the display panel. Thetwo sensor strips are inserted into an aluminum pipe andmounted on the pantographs. The control LEDs integratedin the display panel show the relative position of thepantograph to the contact wire.When the truck moves under the contact wire the indica-tion is activated. The correct position is attained when thegreen LED lights up.lf the truck leaves the correct position the driver is warnedby a yellow LED. There are two yellow LEDs. Depending onthe relative position to the contact wire only one lights upat a time.

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lif,herfiati{ view of csnverl*d truck

lf the driver moves even further away from the correctposition, an orange LED lights up. The red LED meansimminent danger of loss of contact with the wire. lf thetruck loses contact with the strip the pantograph islowered.

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Contact LineF*Hffi*iatiffiflIsAdaption of the foundation pipe lengthsto the local permissible soil pressurestestifies to the fl exibility of the TruckTrolley System even in the initialconstruction phase. This flexibility enhancesthe effectiveness of the foundation workand facilitates any modifications toexisting systems. Coordinates determinedwith the aid of the computer serve thesurveying engineer as a basis for thetopographic positioning of the poles.All foundation bore holes are drilled. Thefoundation pipe lengths are variable andtherefore suitable both for fi lled in groundand for undisturbed soil.

frmter"rmry $ystenm Sirat T?We use our catenary system Sicat TT tobring electrical energy from the substationsto the dump trucks.System overviewThe Truck Trolley System does not featureany tracks to serve as return lines. For thisreason, the overhead catenary systemconsists of two parallel catenarytypecontact lines representing the two phases.One contact line feeds the power to the

After the steel pipes are placed in thefoundation holes (1), they are alignedaccording to the roadway and cast inconcrete. A concrete cap, additionallystrengthened with a preassembledreinforcing cage, ensures greater stabilityof the mast in filled soil (2).Flanges welded to the upper ends of thefoundation pipes serve to fasten thepoles.The poles are standardized and have auniform length corresponding to therequired contact wire height. I

truck, the other acts as the return line tothe substation. Each phase consists of twocontact wires and two messenger wires.Electrical connections are providedbetween the messenger wire and thecontact wire in each section of thecatenary lines. This link ensures a highcurrent-carrying capacity of the overheadsystem without the need of additionalfeeders.

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All messenger wires and contact wiresare tensioned automatically with 10 /12kN each by means of tension wheelequip-ment to ensure that the contactwires and the messenger wires areloaded with the same tensile force atany one time, inde-pendent of theoperating and ambient conditions.This minimizes contact wire wear aswell as overall maintenance andensures a high degree of operatingreliability.The overhead catenary system and thesubstation are linked by means of acentral earthlng system. The earthingcable is strung over the pole topstogether with a supply lead for thelightning. Refl ectors fastened to thecantilevers help the drivers to stay in lane.

lnstallationWhile the foundation works are beingexecuted, the poles and cantilevers canbe prepared for installation. Thecantilevers are preassembled in the sitestore, and the poles are fi tted with allthe necessary fastenings and lightningand signalling equipment before beingtransported to the installation site.The complete pole with the cantilever isplaced in position by means of a crane(3), and is bolted to the foundation.Next, the automatic tension devices,consisting of tension wheel andcounterweights, are installed (a). Thisequipment is designed to exert aconstant tensile force on the messengerand contact wires. independent oftemperature variations. Backstay anchorsof the termination poles permit theabsorption of high tensile forces.

A specially designed working platformis used to string first the messengerwires and then the contact wires (5).The messenger wires are strung viapulleys which are fastened to thecantilevers. At the end of each tensionlength, the messenger wires aretensioned with a pull hoist until thetension wheel assembly disengages andthe counterweights hang free.The locations of the provisionaldroppers are calibrated and marked.Then the two contact wires, which haveto be reeled off the drums at a uniformspeed to prevent kinks forming in thewires, are fastened to the provisionaldroppers. As in the case of the messen-ger wire, tension wheel equipment ateach end of a span ensures thenecessary tensile forces are keptconsta nt.The catenary is regulated from themidpoint anchor to the tensionequipment. During this regulationprocess the contact wires are attached tothe steady arms and aligned horizontally.The operational range of the tensionwheel assemblies is ensured via thecounterweights, taking into considerationthe ambient temperatures. The lengthof each dropper is measured on site;the fi nal droppers are manufactured inthe store before being installed in placeof the provisional droppers (6).Then the insulators and jumpers areinstalled in the contact and messengerwires. Additional contact wires areclamped on to the regular contact wiresin the area of the entry ramp in order toprevent excess wear of the contactwires.A trial operation with empty trucks andwithout current ensures that thecontact wire is properly staggered andthat the necessary clearance is observed.The catenary system is now ready foroperation.Relocation of catenaryThe poles are fastened to the foundationswith fl anges welded to the foundationpipe and to the tubular pole and bolts.This design facilitates the relocation ofthe catenary system. The bolts onlyhave to be loosened and the pole withthe cantilever can be transported to andinstalled at its new location.


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SubstationsSystem overviewThe substations transform and rectifythe AC medium voltage from thepublic or mine's network to thevoltage required in order to ensure theoperation of the trucks on the trolleyline. The substations are connected tothe medium voltage network bymeans of an overhead power line.Design and main componentsThe nominal voltage of the trolleysystem, the power and the number ofsubstations are determined for eachtrolley system accordingly. Theydepend on the electrical requirementsof the trucks as well as on the specificoperating conditions at the mine.During the design phase of thesubstation, heavy dust accumulation,corrosive environmental effects, hightemperatures and 24 hour nonstopoperation have to be considered.The open-type modular design of thesubstation facilitates transport andhandling at site. No foundation work isrequired.The substation only has tostand on a level surface.

It consists of the following main componenls:. the medium voltage switchgear. the rectifier transformers. the rectifier. the DC switchgear. auxiliary equipment (battery, auxiliarytransformer, protection device etc)Except for the rectifier transformer,normally all equipment is housed in anair-conditioned hermetically sealed contai-ner protected from dust and moisture.Erection and installationThe equipment in the substation is delive-red mounted and installed ready forcommissioning, thus reducing the amouniof work to be performed on site. Then i-econtainer, the rectifi er, the auxiliarl,transformer and the connection bet,.'uee'the MV switchgear and the public r:e-,',:'

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Truck Trolley System