WIXLIB

New challenges for the operationof distribution gridsCommunication infrastructures for backhaul and access networksA prerequisite for implementing asolution for this demand is monitoringand managing as many components ofa power supply system as possible allthe way to the consumer. The basisfor this is a reliable communicationinfrastructure. For medium-voltage,at least the following system components must be integrated into a SmartGrid and managed: The key ring-main units All large distributed producers (solar /wind farms, biogas / hydroelectricpower plants, etc.) Large buildings, campuses, refrigerated warehouses, etc.For low-voltage, primarily householdsand small producers of renewableenergy are involved.With respect to their role in the powersupply system, consumers can bedivided into two groups: “Standard consumers”, who havesmart meters and optimize theirelectricity costs via ongoing pricesignals depending on supply anddemand “Prosumers” (prosumer producer consumer), who can feed surplusenergy into the power grid – such assolar power or energy generated bycombined heat and power systems(CHP); many can also intermediatelystore energy using possibilities suchas night storage heaters or e-cars.While the communication requirements for standard consumers areconcentrated on smart meteringincluding price signals, time-criticalcontrol signals and power quality datamust also be transmitted for prosumers. Therefore, in addition to smartmeters, prosumers have energy8gateways, which process and forwardthese control signals accordingly.The young history of Smart Grids hasalready shown that utilities do notimplement it as a whole from thescratch. They usually start with smartmetering projects with later extensions of Smart Grid applications.Already with the first roll-out, thedesign of the communication infrastructure has to consider the growingrequirements for these extensions.After a large deployment of meteringinfrastructure in the first step, it is notacceptable to replace the communication network a few years later becausethe requirements for the next subsetsof Smart Grid applications cannot bemet anymore.Communications infrastructures forall conditionsThe communication infrastructure inthe medium-voltage and low-voltagedistribution systems is usually heterogeneous, and the suitable technologies depend to a large extent on thelocal topology (large city, rural region,distances, etc.). It must therefore bespecifically tailored for each customer.In general, the following communication technologies are available: Fiber-optic or copper communicationcables are the best option, if present Power line carrier systems formedium-voltage and low-voltagenetworks Setup of own private wirelessnetworks (e.g., wireless mesh,private Enterprise-WiMAX / LTE, orUHF Evolution), when spectrum isavailable at reasonable prices orlocal regulations allow for it. Public wireless networks, dependingon the installation for narrowbandcommunication in the kbps range(e.g., GPRS), or in the Mbps range(e.g., LTE). Attractive machine-tomachine (M2M) data tariffs androbustcommunication in case ofpower outages are key ingredients tomake this communication channel aviable option.Depending on the applications beinginstalled inside the RMU, an Ethernetswitch / router might be needed inorder to concentrate the flow ofcommunications. These data concentrators can be implemented as customized solutions or integrated, forexample, in the RTU (remote terminalunit). To meet these requirements,Siemens offers a full range of allabove-mentioned communicationtechnologies including ruggedswitches and routers that complywith energy industry standards.

Fiber opticsEnergy lineEnergy line with PLC communicationMV substationPublic chargingfor e-carsCold storeMVBPL/PLCMV substationMVBPL/PLCMVBPL/PLCMVBPL/PLCMV substation6 kV–22 kVRMU withmeter dataconcentratorMeterCold storeMV substationPublic chargingBuildingfor e-carsRMU withmeter dataconcentrator400 VMVBPL/PLC6 kV - 22 kVMVBPL/PLCMVBPL/PLCRMU400 V400 VLVBPLMeter400 VMeterMeterHomes(smart meter with PLC)400 VMeterRMU400 VRMU400 VRMUSmart homeswith energygatewayDistributedenergy resourcesMeterMeterMVBPL/PLCRMULVBPL400 VLVBPLLVBPLRMULVBPLMeterHomesHomes (smart meterSmart homes with(smart meter with PLC) with wireless connection) energy gatewayEnergy lineMeterHomes (smartmeter with wirelessconnection)MeterLVBPLDistributedenergy resourcesMV Energy line with PLC communicationLV Energy line with PLC communicationFiber-optic infrastructure for distribution networkPower line carrier communication solutions for distribution networksFiber opticsPower line carrier solutionsThe best choice for all communications needsFiber optics is the best transmission medium for mediumand low-voltage applications because it is robust and notsusceptible to electromagnetic disturbances or capacityconstraints. That‘s why grid operators who choose thistechnology will be well prepared when their communications needs multiply in the future. Fiber-optic cables arelaid underground to connect indivi dual substations. Thiswork is associated with heavy civil works, and thereforewith great expense. However, when new power cables areinstalled the cost-benefit analysis paints a clear picture.Fiber-optic cables should generally be the first choice inthis case.For low- to medium-voltage applications,using the existing power lineStandards-based power line carrier solutions provide anattractive communication channel for all applications inmedium-voltage and low-voltage Smart Grid scenarios.They use the utility-owned infrastructure in the distributionnetwork, and provide a reliable and affordable communications channel. Therefore, PLC solutions are especially usefulfor connecting elements in grids, where no other reliablecommunication channel is available. They transform theDSOs assets into a highly capable Smart Grid communication infrastructure. With its throughput, low latency andhigh reliability, PLC solutions serve for distribution automation applications as well as for backhauling data frommetering applications in the medium-voltage grid.Benefits in detail: At the core of a variety of communications systems, frompassive optical networks (PON) to Ethernet and SDH Durable, insusceptible to electromagnetic disturbances Practically unlimited transmission capacityAs with every communication technology, the transmissionrange and bandwidth provided by the PLC solution dependson the quality of the used transmission medium. In case ofthe transmission over power lines, type and age of thepower cable as well as the number of joints have an impacton the achievable results. Consequently, a PLC networkneeds to be engineered and planned correctly to providemaximum performance.Benefits of power line communication solutions: They transform the utility-owned infrastructure intoa highly capable communication network. They are especially useful for connecting all elements inthe grid where there are no other reliable communications media available. They provide a communication solution for all MVpower grids.9

CommunicationEnergy lineEnergy line withPLC communicationMVsubstationMVsubstationMV substationMV substation6 kV–22 kV6 kV–22 kVService carRMU withmeter dataconcentrator400 V 400 VMeterCommunicationEnergy lineEnergy line withPLC communicationMeterMeterMeterRMU400 VRMU400 VRMURMU withmeter dataconcentrator400 V 400 V400 VRMU400 VRMUMeterMeterHomes(smart meter with PLC)RMUHomes (smartmeter withwireless connection)Smart homeswith energygatewayDistributedenergy resourcesMeterMeterMeterHomes(smart meter with PLC)MeterHomes (smartmeter withwireless connection)Smart homeswith energygatewayDistributedenergy resourcesEnterprise-WiMAX / LTE solution for distribution networksWireless mesh networkEnterprise-WiMAX / LTEWireless meshThe main application area for private WiMAX / LTE systems,specifically tailored to the needs of enterprises in verticalmarkets, is backhauling of RMUs, data concentrators orDistributed Energy Resources (DER). Single prosumers couldtechnically be served, but this is economically reasonableonly in selected cases. WiMAX (Worldwide Interoperabilityfor Microwave Access) is a standards-based telecommunications protocol (IEEE 802.16 series) that provides bothfixed and mobile broadband connectivity. The advancedpoint-to-multipoint technology is field-proven and deployed globally. In the past, certain manufacturers haveevolved the system for the requirements of specific verticalmarkets such as oil and gas or power utilities. Differingfrom telecommunication-carrier-oriented systems, theseimplementations support special features such as asymmetric prioritization of uplink traffic, layer-2-based traffic(multicast / IEC 61850 GOOSE), redundancy options, aswell as economic system scaling fitting also for smaller,privately owned regional or local networks.In general, wireless mesh networks are composed ofcooperating radio nodes that are organized in a meshtopology. The link communication technology from onehop to another can be standardized (e.g., IEEE 802.11series [WiFi] or IEEE 802.15.4 [LoWPAN, Low-rate WirelessPersonal Area Network]) or proprietary (e.g., FHSS, OFDMtechnologies). The mesh protocols and correspondingforwarding algorithms are on the other hand still predominantly proprietary. Standardization efforts in this area(e.g., 6LoWPAN protocol suite / Zigbee-NAN) are currentlystill ongoing. Thanks to their mesh properties along withself-setup and self-healing mechanisms, mesh networksinherently offer ease of operation and redundancy for fixedapplications. The system performance can be characterizedby the hops’ throughput capacity, the average reach of ahop-to-hop link, and the max. number of hops on a singlepath.Besides the application requirements, it is important toassess regional conditions like area topology and availability of radio spectrum. Professional radio networkplanning and network engineering are mandatory whensetting up private broadband radio networks.BenefitsThe WiMAX technology is field-proven, globally deployed,and continues to evolve. In parallel, manufacturers are alsopreparing enterprise-grade shapings of LTE-based networksleveraging economy-of-scale benefits from the widelyspread deployment of this technology in the public cellulardomain. Enterprise-WiMAX / LTE networks can be scaledfrom small to large, which allows for privately ownednetworks even on regional and local levels.10Detailed requirements as well as specific regional conditions must be carefully assessed in order to select thebest-suited technology.Broadband wireless mesh for RMU / DER backhaulBroadband wireless mesh systems have sufficient transportcapacity to backhaul a high amount of data, that is to sayaggregated data of various RMUs / DER plants, withmultiple RTU devices or data concentrators / access gateways.Narrowband radio frequency (RF) mesh for access /meteringThe term “RF mesh system” is used to denominate narrowband wireless mesh technologies. Their capacity suffices toconnect individual devices with moderate data transmission requirements, such as meters, grid sensors, measuringtransformers, etc. The single RF mesh nodes communicate

One base station forseveral MV substationsCommunicationEnergy lineMV substationMVsubstationMV substationServicecar6 kV–22 kV400 V 400 VRMU400 VRMU400 V6 kV–22 kV400 VRMUMeterMeterMVsubstationRMU withmeter dataconcentratorRMU withmeter dataconcentratorMeterCommunicationEnergy lineEnergy line withPLC communicationMeterMeterHomes(smart meterwith NB-PLC)MeterHomes (smartmeter withwireless connection)Smart homeswith energygatewayDistributedenergy resourcesUHF evolution solutionvia each other towards an access gateway, which serves astake-out point into other WAN / backhaul communicationnetworks.BenefitsThanks to their mesh properties along with self-setup andself-healing mechanisms, mesh networks inherently offerease of operation and redundancy for fixed applications.UHF evolutionThe private wireless communication technologies coveredin the previous sections (Enterprise-WiMAX / LTE andbroadband wireless mesh) represent the preferred solutions for easily extensible multi-purpose wireless communication networks. However, for singular applications withjust modest data rate requirements and end points spreadover a large geographical area, an extensive privatebroadband wireless infrastructure can not always beimplemented with a positive benefit-cost ratio. In thesecases, the recently enhanced UHF radio systems (for thesake of distinction from classical UHF, here denominatedas UHF evolution) constitute a better match for these kindsof requirements.Basic technical data: Data rates: purpose-fit bandwidth 100 kbps Coverage: up to dozens of kilometresMeterMeterHomes(smart meter with PLC)400 V RMUMeter400 VRMU400 VRMUMeterHomes (smartmeter withwireless connection)Smart homeswith energygatewayDistributedenergy resourcesPublic cellular networkselective rollouts and including rurally distributed gridassets. The systems provide the merits of modern radiocommunication including automatic scalability betweenthroughput and range. Due to the deployment of licensedspectrum and the flexibility of private network design,they are also appropriate for mission-critical applications.Public cellular networksFor the extension of private communications networksThe main application areas for public mobile radionetworks in the smart-grid context are meter reading andenergy grid monitoring functions.In contrast to constructing new, proprietary networksfor smart-grid communication, there is also the option ofusing existing cellular radio networks owned by communications service providers. These networks are standardsbased, deployed worldwide, and continuously upgradedand expanded. Activities like acquiring spectrum licenses,building, operating, and maintaining the network as wellas assuring sufficient coverage and bandwidth on anationwide scale are naturally managed by the communications service providers. Data rates normally availablerange from 50 kbps (GPRS), over 15 Mbps (HSPA), to over20 Mbps (LTE). Attractive data tariffs and the availabilityof the network are key to use public cellular networks forsmart-grid applications. Implementations in licensed radio spectrum, withnarrow-band spectrum usually readily available toutilities.BenefitsUHF evolution is ideally suited for applications withmoderate bandwidth requirements (e.g., monitoringor automation via IEC 60870-5-104), even in case of just11

Transmissionnetworks12

Solutions for transmission grids(communication backbone)Fiber-optic communications on the way to carrier and utility grade packettransport networks.Today – Synchronous Digital Hierarchy (SDH) plusPlesiochronous Digital Hierarchy (PDH) access multi plexer solutionsToday, SDH solutions in combination with PDH accessmultiplexer are used mostly by utilities for the communication requirements in high-voltage networks. Siemens offersfor these demands the latest generation of SDH equipment,commonly referred to as NG (Next Generation) SDHsystems or Multi-Service Provisioning Platforms (MSPP).NG SDH technology combines a number of benefits thatmakes it still well-suited to the needs of power utilities.Among those benefits are high availability, comprehensivemanageability, and monitoring features. Ethernet-over-SDHprovides the capacity to transport packet-based traffic overthe SDH backbone with high reliability and low latencies.State-of-the-art NG SDH systems are highly integrated,providing the requested capabilities for utilities in a singledevice.Migration to highly available (carrier and utility grade)Multi-Protocol Label Switching (MPLS) networksThe SDH technology, combined with PDH multiplexer, isa well-proven solution for the manifold communicationrequirements of the transmission utilities.But meanwhile new requirements arise, which clearlyidentify the limits of the SDH / PDH technology. Especiallythe demand for further cost savings, above all the OPEXpart, is the main challenge for the communication departments of the utilities. At the same time, the portion ofpacket-based data (Ethernet and IP) in the wide areanet-works, caused by new Ethernet- and IP-based systems(e.g., new IEC 104 RTUs, IEC61850 protection systems,sensors, IP telephony, IP CCTV, etc.) is increasing dramatically.At the subscriber side there is still a need to operate anumber of different systems with conventional communication interfaces in today’s substations (e.g., FXS, FXO,E&M, V.24, X.21, etc.). For this purpose, so-called PDHaccess multiplexers are used, which provide the requestedinterfaces, bundle the communication signals, and passthem on to the NG-SDH systems.The fig shows a typical NG-SDH solution with connectedPDH Access SDHRouterAccessMUXIEC 61850substation ringPhoneRTUControlcenterAccessMUXIEC 61850substation ringPhoneRTUTypical NG SDH solution for transmission grids13

In order to follow the general trend of the telecom industryand the roadmaps of the network manufacturers, theexisting traditional communication networks need to bemigrated into highly available, packet-based hybrid systemswith low latency.The fig shows a typical MPLS communication network.In a final stage, Ethernet would be the single communication interface, which will be used in the backbone as wellas in the access network.The most important requests are:Based on this easy network structure in combination with apowerful Network Management System (NMS) and intelligent network functions, daily network configuration tasksand other service work can be performed fast and straightforward. This is the basis for further OPEX reductions. Cost-optimized installation and operation of the networkBenefits of a MPLS communication network Low latency, jitter- and connection-oriented services Exceptionally cost-efficient operation of the network Use for critical Smart Grid applications (e.g., distance anddifferential protection) Supports all latency critical Smart Grid applicationsHowever, these packet-based optical networks need tomeet the specific communication requirements of thetransmission network operators. Easy network extension SDH-like look-and-feel (e.g., central NMS, fixed communication paths) Support of conventional PDH communication interfaces. Efficient use of the available transmission bandwidthIn order to meet these requirements, it is advisable tostepwise migrate the installed SDH / PDH communicationinfrastructure to a packet-based, highly available (carrierand utility gra

today’s transmission systems, almost all substations are monitored and controlled online by Energy Management Systems (EMS). The main transmission lines are usually equipped with fiber-optic cables, mostly integrated in the earth (ground) wires (OPGW: Optical Ground Wire) and the substa