The Standardization Of Distribution Grid Communication .
1The Standardization of Distribution GridCommunication NetworksZhao Li, Member IEEE, Fang Yang, Member IEEE, Dmitry Ishchenko, Member IEEEAbstract--This paper reviews the recent development in thedistribution utility communication networks including theadvanced metering infrastructure (AMI) and the supervisorycontrol and data acquisition (SCADA) system. Thestandardizations of application level communication protocols inboth AMI and SCADA systems are the major focus of this paper.In addition, some smart grid applications facilitated by theadvances in the distribution communication networks are alsodiscussed.Index Terms-- Smart Grid, AMI, SCADA, CommunicationProtocol.AI. INTRODUCTIONPromising solution for challenges presented by theglobally rising energy demand, aging power systeminfrastructures, increasing fuel costs, and emerging renewableresource portfolios is the smart grid [1]. Technically, smartgrid applies the advanced monitoring and control technologiesto the electric grid, which enables sustainable options tocustomers and improves security, reliability, and efficiency forutility grid operation [2], [3].Since one primary goal of the smart grid is to improveenergy efficiency, it is often referred to as the “green grid”.Two green features of the smart grid are that it maximizes theutilization of renewable resources (e.g., solar and wind) andimproves the efficiency of system operation through lossreduction, dynamic pricing, and other applications. On theother hand, different from a traditional system in which powergeneration and consumption can be well planned andestimated, in smart grid, the power generation andconsumption become more dynamic and unpredictable due tothe intermittence of renewable resources and dynamic pricedriven power consumption. The unpredictable powerproduction and consumption complicates the gridmanagement. To efficiently manage a grid system with thesedynamic features, utility control centers should be able tomonitor and control the grid in real-time.Utility control centers implement system monitoring bycollecting measurements from field devices (e.g., smartFinancial support from the ABB Corp. Research Center is gratefullyacknowledged. The authors appreciate the discussions and help fromcolleagues Zhenyuan Wang and Xiaoming Feng.The authors are with the ABB US Corp. Research Center940 Main Campus Dr. Suite 200, Raleigh NC, 27606, United StatesEmail: {zhao.li, fang.yang, Dmitry.ishchenko} @us.abb.com978-1-4673-2729-9/12/ 31.00 2012 IEEEmeters, sensors, and intelligent electronic device (IED)) andsystem control through sending control commands tocontrollable equipment. As transported messages carryinformation of system status and/or control that are importantto maintain the normal operation of the system, particularlywhen the grid is hit by a large disturbance, the communicationnetwork should ensure the instantaneous deliverability ofimportant messages. If a control center fails to deliver orallows the delay of delivering such a message, it may lose theopportunity to govern a disturbance and potentially render thegrid system unstable and unreliable. Hence, building a largescale real-time communication network becomes one ofimportant pre-requests for Smart Grid [4].Nowadays, distribution utilities mainly adopt two types ofcommunication networks: the supervisory control and dataacquisition (SCADA) system [5], [6] and the advancedmetering infrastructure (AMI) [7]. In the past several decades,SCADA has played a key role in the online monitoring andcontrol of the grid system. However, constrained by high costson constructing a real time communication system, SCADAhas been mainly deployed in transmission system and a smallpart of distribution system (e.g., distribution substations) forreal-time monitoring and control. In contrast, because ofrelatively low cost on building a non-real-time communicationsystem and the stimulus from US government, AMI has beenwidely deployed in the distribution system recently, reachingthe feeder and residential levels. Rather than functioning as amonitoring and control network, AMI implements aninfrastructure to automatically collect energy usages fromresidential smart meters and transports them back to thecontrol center on a monthly basis. It improves the efficiencyof the process of collecting residential energy usages and thequality of collected measurements, and eventually enhancesthe quality of customer service.In the past several years, efforts have been invested intobuilding the large scale smart grid communication networksreaching the feeder level or the residential level. These effortsinclude extending the scope of SCADA and/or enhancing thereal-time capability of AMI. With the scope of the monitorednetwork reaching the feeder and residential level, the numberof monitored data points is significantly increased, reachingmillions. Hence, improving efficiency and quality of the smartgrid communication network and increasing interoperabilitybetween devices produced by various vendors becomeimportant topics and lead to the standardization of thecommunication protocols and information models.This paper primarily reviews the efforts on standardizationof application level communication protocols in both SCADA
2[9] and AMI [10] recently. The rest of this paper is structuredas follows: focusing on AMI infrastructure, the second sectionfirst introduces its components, and then discusses thestandardization of the AMI protocols. Similarly, the thirdsection discusses SCADA and recent standardization efforts.Section four discusses some potential advanced smart gridapplications triggered by real-time and/or near real-timesmart-grid communication networks. Section five concludesthis paper.support new requirements (i.e., demands responses) from thesmart grid [11].The standardization of the AMI infrastructure includes thestandardization of both AMI communication protocols andAMI information models.Table 1 Communication modules supported by AMI vendorsAMI VendorsLandis GyrItronII. ADVANCED METERING INFRASTRUCTUREElsterA. BackgroundAMI consists of metering, communication, and datamanagement functions, offering the two-way transportation ofcustomer energy usage data and meter control signals betweencustomers and utility control centers. The AMI was originallydeveloped from advanced meter reading (AMR) [12], [13],[14], [15], and [16], a one-way communication infrastructurethat implements automatic collection of meter measurementsfrom residential smart meters to utility control centers forcalculating monthly bills and fulfilling other related activities.Partially as the next generation of “AMR”, AMI not onlyenhances the traditional data collection functionality (i.e.,improving monthly meter data collection to real time or nearreal-time meter data collection) but also develops the remotecontrol capability from the control center to smart meters.Motivated by the economic stimulus plan of the U.S.government, most U.S. states have begun the process ofdeploying smart meters within AMI infrastructures. At thebeginning of 2009, for example, Texas initiated a project ofdeploying six million smart meters and expected to completeit by 2012; and California plans to install 10 million smartmeters by the end of 2012. The deployment of smart meters istaking place not only in the United States but throughout theworld. Based on current estimates, by 2015, smart meterinstallations are expected to reach 250 million worldwide[17]. Hence, for most utilities, AMI will be a well-deployedfeeder or residential level communication network, deliveringa large amount of data in real time or near real time (e.g.,every 15 minutes).B. The Standardization of the AMI InfrastructureIn the current market, smart meters from different vendorsare using proprietary communication protocols that aregenerally non-interoperable (Table 1). For utilities, deployingmillions of smart meters is a long-term investment indeed.Therefore, once a utility adopts smart meters from a certainAMI vendor, it must follow up with related products from thesame vendor for the sake of compatibility.As utilities are reluctant to commit to a certain metervendor, enabling interoperability between AMI products fromdifferent vendors by following the same standards becomes aneffective way to protect utilities’ investment. Table 2 listspopular standard communication protocols and meterinformation models in the current market, defined by ANSI,IEC and IEEE. Most of them have recently been revised (e.g.,C12.18 and C12.19) or newly defined (e.g., C12.22) toCommunication ModulesUnlicensed RF, PLCZigbee, unlicensed RF, Publiccarrier network (OpenWay)Unlicensed RF, public carriernetworkEchelonPLC, RF, EthernetGEPLC, public carrier network, RFSensusLicensed RF (FlexNet)EkaUnlicensed RF (EkaNet)SmartSynchPublic carrier networkTantalusRF(TUNet)TriiliantZigBee, public wireless networkThe Standardization of AMI Communication ProtocolsIn the past two years, the focus of the standardization ofAMI communication protocols has gradually shifted from thephysical level (e.g., ANSI C12.18 [18]) and the device level(e.g., ANSI C12.21 [20]) to the application level (e.g., ANSIC12.22 [21]) because application level communicationprotocols effectively isolate the details of underlying physicalnetwork configurations and implementation. This sectionintroduces two application level communication protocols thatare popular in both the United States (i.e., C12.19 and C12.22)and European markets (i.e., IEC 62056-53 and IEC 6205662).ANSI C12.22Historically, after a set of standard table contents andformats were defined in ANSI C12.19, a point-to-pointstandard protocol (ANSI C12.18) that transported the tabledata over an optical connection was developed. Afterwards,the “Protocol Specification for Telephone ModemCommunication” (ANSI C12.21), which allowed devices totransport tables over telephone modems was defined. TheC12.22 standard, expanding on the concepts of both the ANSIC12.18, and C12.21 standards, allows the transport of tabledata over any reliable networking communications system.The goal of the ANSI C12.22 standard is to define ameshed network infrastructure customized for AMIapplications. The standard contains the followingfunctionalities:1) Defining a datagram that may convey ANSI C12.19 datatables through any network, including the AMI specificnetwork and general purpose network (e.g., Internet)2) Providing a seven-layer communication infrastructure forinterfacing a C12.22 device3) Providing an infrastructure for point-to-pointcommunication that will be used over local ports (e.g.,optical ports and moderns)
34) Providing an infrastructure for efficient one-way messagingThe ANSI C12.22 mesh network consists of the C12.22nodes and network. A C12.22 node, a point on the networkthat attaches to a C12.22 network, is a combination of both aC12.22 device and communication module. The C12.22communication module is a hardware module that attaches aC12.22 device to a C12.22 network. The C12.22 devicecontains meter data in the forms of tables defined by C12.19.The interface between the communication module and thedevice is completely defined by the C12.22 standard.Table 2 Popular standard information model and communication tDomainC12.19[19]2005InformationmodelUtility industry end devicedata tionProtocolProtocol specification forInterfacingto data 8]2005CommunicationProtocolProtocol specification forANSIType 2 optical onProtocolProtocol for 1968-9[22]2009InformationModelMeter data model in powerdistribution protocolCOSEM application InformationprotocolMeter object 26]2007InformationprotocolInterface for dataexchangingGas,Water,Electricity1701 [27]2011CommunicationprotocolOptical PortCommunication Protocol(compatible with 702 [28]2011CommunicationprotocolTelephone moderncommunicationprotocol (compatible withC12.21)P1377/D9[29]2011InformationModelEnd device data tables(Compatible with AN/WAN Nodecommunicationprotocol(Compatible with C12.22)Gas,Water,ElectricityP1703/D8[30]2011The C12.22 network defines an AMI specific meshcommunication infrastructure that consists of one or moreC12.22 network segments (a sub-network) or a C12.22 LAN.Similar to the open system interconnection (OSI) model, theC12.22 communication protocol consists of seven layers(Figure 1): an application layer (layer 7), a presentation layer(layer 6), a session layer (layer 5), a transport layer (layer 4), anetwork layer (layer 3), a data link layer (layer 2), and aphysical layer (layer 1). Unlike OSI, C12.22 is customizedonly for meter data transportation. For example, theapplication layer of C12.22 supports only ANSI C12.19tables, described by EPSEM and ACSE, the languages thatencapsulate C12.19 meter data.Supported by layers 1 through 6, which consist of variousphysical network connections in the meter industry as well asthe standard Internet connection, the C12.22 standard definesthe following services in the application layer of the OSImodel (layer 7): an identification service, a read service, awrite service, a security service, a trace service, and others.IEC62056IEC62056 defines the meter interface classes for theCompanion Specification for the Energy Metering (COSEM)model through a series of standards on data exchange formeter reading, tariffs, and load control. Similar to ANSIC12.22, IEC62056-53, the application layer communicationprotocol in the COSEM model, is defined based on severalother IEC62056 series protocols, including IEC62056-21, 42,46, and 47 [23]. Except for the IEC62056-21, which is used inhand-held devices for locally exchanging data with meters, theremaining protocols define the various layers of thecommunication network that support application levelcommunication: the physical layer (IEC62056-42), the datalink layer (IEC62056-46), and the transport layer (IEC6205647). Similar to ANSI C12.22, the meter data carried byIEC62056-53 are defined by IEC62056-61 and IEC62056-62,which are dedicated meter data models in the IEC62056series.C12.22 DeviceC12.22 Communication ModelC12.19 TablesC12.22 EPSEMC12.22 ACSEC12.22 Layer 7C12.19 TablesC12.22 EPSEMC12.22 ACSEC12.22 Layer 7C12.22Layer 6 to 1C12.22Layer 6 to 1Key:C12.22Layer 6 to 1To LAN/WAN/MANLAN – Local Area NetworkWAN - Wide Area NetworkMAN – Metropolitan Area NetworkFigure 1 The open system interconnection (OSI) model defined by C12.22As an application layer communication protocol,IEC62056-53 primarily offers three types of services in itsapplication-level: the GET service (.request, .confirm), theSET service (.request, .confirm), and the ACTION service(.request, .confirm).Although both IEC62056-53 and ANSI C12.22 provide asimilar way to construct the advanced mesh AMI network,each has a unique market focus: IEC62056 primarily focuseson the European market while ANSI C12.22 focuses on theNorth American market. In the current North Americanmarket, most AMI vendors support C12.18 and C12.21, butfew support C12.22 since it has only recently been defined.Because of the advantages of C12.22 and/or IEC62056-53, wepredict that most major meter vendors will support either ofthem worldwide in the near future.The Standardization of AMI Information ModelAn information model is a representation of concepts,relationships, constraints, rules, and operations that specifydata semantics for a chosen domain of discourse [32]. In theAMI communication infrastructure, it is necessary to have an
4information model, by which all communication participantscan semantically reach a certain level of understanding.This section discusses major standard information modelsin today’s market: ANSI C12.19 and IEC62056-62. Theformer is supported by ANSI C12.22 and widely used in theNorth American market; the latter is support by IEC 62056-53and widely deployed in the European market.ANSI C12.19-2008ANSI C12.19 resulted from comprehensive cooperativeeffort among utilities, meter manufacturers, automated meterreading service companies, the ANSI, Measurement Canada(for Industry Canada), NEMA, the IEEE, Utilimetrics, andother interested parties. Currently, it has two versions: ANSIC12.19-1997 and ANSI C12.19-2008. As the latter is intendedto accommodate the concepts of the most recently identifiedadvanced metering infrastructure, it is the primarily focus ofthis section.The heart of ANSI C12.19 is a set of defined standardtables and procedures: The former are methods of storing thecollected meter data and controlling parameters, and the latterare methods of invoking certain actions against the above dataand parameters [19]. The standard tables in C12.19 aretypically classified into sections, referred to as “decades”.Each decade pertains to a particular feature set and a relatedfunction. Transferring data from or to an end device thatadheres to the C12.19 standard entails reading or writing aparticular table or a portion of a table. Even though theC12.19 standard covers a broader range of tables andprocedures, it is highly unlikely that any smart meter will beable to embed all of the tables or even a majority of thosedefined in ANSI C12.19. Hence, implementers are encouragedto choose an appropriate subset that suits their needs.The C12.19 standard is a general meter information modelthat serves various domains, including electricity, water, andgas using a series of tables, which can be customized throughseveral standard operations.IEC 62056-62Unlike ANSI C12-19, which uses tables to package metermeasurements, IEC 62056-62 models meter informationthrough a series of interface classes. As the informationmodeled by C12.19 and IEC 62056-62 are nearly identical, wedo not duplicate our efforts to further introduce the content ofIEC 62056-62. Similar to ANSI C12.19, as a general meterdata model, IEC 62056 supports not only electricity metersbut also gas and water meters.For AMI vendors, the preference to support certainstandards reveals a strong geographical bias. For example,most smart meter vendors in the North American market aremore likely to choose ANSI series standards (i.e., C12.19 andC12.22) while those in the European market are more likely toselect IEC standards.Triggered by the rapid development of the smart grid,beyond supporting proprietary communication protocols, mostAMI vendors have begun to support the standardcommunication protocols and meter data models.III. SCADA –THE UTILITY MONITORING AND CONTROLNETWORKA. BackgroundHistorically, the most matured utility applications havingclose relationships with communication technologies istelemetry and telecontrol, which are commonly fulfilled by asupervisory control and data acquisition (SCADA) system, areal-time communication network bridging end devices andutility control centers. Constrained by the high cost ofconstruction, SCADA has traditionally been limited at thetransmission level and distribution system substations, onlymonitoring and control important power system devices.As SCADA has been in place since the late 1960s, it hastransitioned through several generations of communicationtechnologies and protocols. Initially, RS-232 and RS-485were used as physical interfaces with Modbus, DNP, or IEC60870-5-101 [36] as communication protocols in SCADA.Since the late 1990s, Ethernet interfaces have become the defacto standard for most of the IEDs, and traditional serialbased protocols have begun to support Ethernet interfaces intheir physical layers, but the application layer of aboveprotocols is still serial fashion; for example, Modbus and IEC60870 evolved into Modbus over TCP and IEC 60870-5-104[37]. During the transition, DNP3 has become the mostimportant utility communication protocol, particularly in US,and has been developed into an IEEE Standard, named IEEE1815, [38] in 2010.Unlike DNP3, evolved from traditional communicationprotocols, IEC61850 is a newly defined network basedcommunication protocol optimized for the mesh network.Beyond defining communication specifications, IEC61850primarily delimits an information model that is compatible tothe common information model (CIM) [31], the widelydeployed information model in the power system domain.Hence applications based on IEC61850 have stronginteroperability with most power system applications in stateof the art.Nowadays, IEC61850 has been identified as one of the keystandards that lay the foundation of the future Smart Gridframework by the US Federal Energy Regulatory Commission(FERC) in 2010. In this section, DNP3 and IEC61850 arebriefly discussed.B. Distributed Network Protocol 3 (DNP3)Developed and maintained by the DNP3 Users Group, anopen community for vendors and utilities, DNP3 is recognizedas an important utility communication protocol, particularly inthe US market. Structurally, even though DNP3 supportsEthernet in its physical layer, it still keeps the serial nature inits application layer. Hence, from application’s point of view,DNP3 is still a serial communication protocol.As saving communication bandwidth was one of the mostcritical goals that the DNP series protocols were trying toachieve, DNP3 is suitable for situations where communicationresources (e.g., bandwidth) are limited. Structurally, DNP3 isconstructed based on a simplified OSI model, including onlythree layers: the application layer, the data link layer, and thephysical layer.
5Figure 2 demonstrates the master-outstation communicationmodel of DNP3 [38], which includes a masterdevice/information collectors (e.g., an RTU or SCADAmaster) and one or more outstation devices/end devices (e.g.,IEDs) connected to each other using serial or Ethernet links.Here, inputs are values collected by outstation and outputs arecommands sent by SCADA masters. Generally, an outstationcontains several arrays of data points in different types (e.g.,binary and analog), mapping to various internal deviceparameters in the outstation firmware.Rather than having a formal information model, DNP3defines the following classes to organize data: Class 0: Staticdata – the snapshot of the outstation current point values;Classes 1, 2, 3 – the historical point data from the outstationevent buffer. Semantically, the above classes are mapped to arange of data points in outstations.the application layer confirmation from the master is receivedor the final confirmation timeout is expired.C. IEC 61850IEC61850 is maintained by the International Electrotechnical Commission Technical Committee 57. Technically,IEC61850 has been developed based on utilitycommunications architecture (UCA), an open communicationsstandard for the electric power utilities defined by ElectricalPower Research Institute’s (EPRI) in the early 1990s.IEC61850 was originally designed for exchanginginformation within substations. Afterwards, it expandsconcepts and principles beyond the substation fence.Unlike DNP3, IEC 61850 consists of a series specifications[39], primarily focusing on the following aspects: theinformation model and communication structure (IEC618507), the mapping of communication service (IEC61850-8 andIEC61850-9), and configuration description (IEC61850-6).Located in the heart of IEC61850 is information modelingpart (IEC 61850-7). To some extent, IEC61850 is more like aninformation model, modeling the information exchangedbetween devices in a substation.Representing a logical function performed by a physicaldevice, a Logical Node (LN) is a basic information unit in IEC61850, the semantic of which is represented by data and dataattributes (Figure 3: the LN for a circuit breaker [39]). Agroup of LNs constructs a Logical Device (LD), representingvarious functions performed by a physical device (e.g.,protection, control, and monitoring). Generally, a physicaldevice consists of one or more LDs. In 61850, over 100 LNsare defined, covering the functionalities across protection,monitoring, and control of a grid system.Logical nodeXCBRFigure 2 The communication model of DNP3 [38]As reducing the network traffic is one major focus ofDNP3, it introduces the concept of deadband, allowinggeneration of events based on monitoring the analog inputsagainst thresholds (deadbands). An analog input onlygenerates an event when changes of its absolute value exceeda predefined threshold (deadband) so that the smallfluctuations of the analog value mapped to the analog inputare filtered out and will not be reported.In DNP3, SCADA masters can poll data from outstationsby sending a request to the outstations. Meanwhile, theoutstations can push data back to a master through amechanism of spontaneous unsolicited reports. During thepushing process, the outstation initiates the reporting processwhen it accumulates a pre-determined number of class events.In addition, to save the bandwidth, DNP3 supports the reportby-exception (RBE) function, by which the outstation onlyreports the data that has changed since the last poll. The RBEfunction significantly reduces the amount of information thatmust be transferred, saving the bandwidth.To guarantee the information delivery, the followingstrategy is adopted by DNP3: if the original unsolicitedreporting attempt failed, the outstation initiates a retry untilData-DataAttributesPosControl value ‘ctlVal’Operate timeOriginatorControl numberStatus value ‘stVal’QualityTime stamp.Subst. enableSubst. value.Controlscontrollablecontrolstatus valuestatussubstitutionPulse configurationconfiguration,Control modeldescriptionSBO timeoutSBO classand extension.Figure 3 Hierarchical structure of IEC61850 object model[39]In IEC61850, the object models (e.g., LN and LD) can beaccessed through abstract communication service interfaces(ACSI). Some typical services provided by ACSI include thefollowing:(1) The SETTING-GROUP-CONTROL BLOCK, switchingthe field device from one set of preconfigured controlparameters to another set(2) The REPORT-CONTROL-BLOCK, LOG-CONTROLBLOCK, reporting and logging the event data, including
6immediate real-time reporting, polled reports, and integrityscans(3) A generic substation event (GSE) and a generic objectoriented substation event (GOOSE), enabling fast peer-to-peercommunications among the field devices and allowing theimplementation of de-centralized control schemes based onlocal intelligence(4) Control class model, performing the control actions,supports both direct control and select-before-operate controlwith enhanced securityThe network interface maps the services defined by ACSIto actual network protocols. The protocol profiles of IEC61850 are defined by the Manufacturing MessageSpecification (MMS) protocol, the Internet, and OSI protocolstacks. In addition, the Ethernet (IEEE 802.3x) LAN is alsospecified for high-speed protection functions, such as GOOSEand the processing of digitized waveforms of high samplingrates (Sampled Values). The infrastructure of 61850 issummarized in Figure 4.Information ModelLogical Device, Logical Nodes, Attributes, and DataIEC 61850-7-4/-7-3Abstract Communication Service Interface(i.e., SETTING GROUP CONTROL BLOCK, GOOSE) IEC 61850-7-2Network InterfaceMapping to MMS, Ethernet (TCP/IP)discusses.A. Smart grid communication systemFrom information point of view, CIM, including IEC61970and IEC61968, is the widely applied information model in thegrid management territory. Most power system applicationsare built on top of it. Therefore, the information collected bythe AMI and SCADA has to be translated to CIM beforebeing consumed by these applications. For the gridmanagement system, information sent from AMI to the gridmanagement system has to be translated from C12.19 toIEC61968-9, the newly defined meter data model in CIM;while the information sent from SCADA has to be convertedinto IEC61970 and/or IEC61968. On the other hand,information sent from the grid management system to AMIand/or SCADA has to be changed from CIM to C12.19 and/orIEC61850 separately.Beyond accommodating different types of informationmodels, we have to consider adapting the communicationprotocols when integrating AMI and SCADA with the gridmanagement system. For example, to receive/send informationfrom/to AMI or SCADA, the grid management system needsto have a C12.22 interface or IEC61850-8 interface. Toillustrate the above integration process, the informationintegration layer is proposed in Figure 5.IEC 61850-8-1Physical LinkKey:MMS Manufacturing Message SpecificationIn summary, DNP3 is a serial communication protocol:even though supporting Ethernet in its physical level, DNP3still maintains the serial manner in its logical level. Comparedto IEC61850, DNP3 has less communication overhead and ismore suitable for low bandwidth network in practice. Incontrast, IEC61850 has a well-defined information model thatis compatible with CIM, the most popular information modelused in the power system domain. Hence, IEC61850-friendlydevices have less overhead in semantic translation whenintegrated with most power system applications. However,transporting the complex semantics modeled by IEC61850consumes a large amount of network resource, requiring awell-constructed communication network in the physicallayer.IV. SMART GRID COMMUNICATION NETWORK AND SMARTAPPLICATIONSFigure 5 illustrates the landscape of the standard-basedsmart grid system, including the smart grid communicationsystem and the grid management system. The communicationsystem includes AMI and SCADA; while the grid applicationsincludes some advanced distribution management applicationsenhanced by real-time or near real-time communicationnetwork. These two parts
ANSI C12.22 Historically, after a set of standard table contents and formats were defined in ANSI C12.19, a point-to-point standard protocol (ANSI C12.18) that transported the table data over an optical connection was developed. Afterwards, the “Protocol Specification for Telephone Modem Communication”
May 02, 2018 · D. Program Evaluation ͟The organization has provided a description of the framework for how each program will be evaluated. The framework should include all the elements below: ͟The evaluation methods are cost-effective for the organization ͟Quantitative and qualitative data is being collected (at Basics tier, data collection must have begun)
Silat is a combative art of self-defense and survival rooted from Matay archipelago. It was traced at thé early of Langkasuka Kingdom (2nd century CE) till thé reign of Melaka (Malaysia) Sultanate era (13th century). Silat has now evolved to become part of social culture and tradition with thé appearance of a fine physical and spiritual .
On an exceptional basis, Member States may request UNESCO to provide thé candidates with access to thé platform so they can complète thé form by themselves. Thèse requests must be addressed to esd rize unesco. or by 15 A ril 2021 UNESCO will provide thé nomineewith accessto thé platform via their émail address.
̶The leading indicator of employee engagement is based on the quality of the relationship between employee and supervisor Empower your managers! ̶Help them understand the impact on the organization ̶Share important changes, plan options, tasks, and deadlines ̶Provide key messages and talking points ̶Prepare them to answer employee questions
Dr. Sunita Bharatwal** Dr. Pawan Garga*** Abstract Customer satisfaction is derived from thè functionalities and values, a product or Service can provide. The current study aims to segregate thè dimensions of ordine Service quality and gather insights on its impact on web shopping. The trends of purchases have
Chính Văn.- Còn đức Thế tôn thì tuệ giác cực kỳ trong sạch 8: hiện hành bất nhị 9, đạt đến vô tướng 10, đứng vào chỗ đứng của các đức Thế tôn 11, thể hiện tính bình đẳng của các Ngài, đến chỗ không còn chướng ngại 12, giáo pháp không thể khuynh đảo, tâm thức không bị cản trở, cái được
Le genou de Lucy. Odile Jacob. 1999. Coppens Y. Pré-textes. L’homme préhistorique en morceaux. Eds Odile Jacob. 2011. Costentin J., Delaveau P. Café, thé, chocolat, les bons effets sur le cerveau et pour le corps. Editions Odile Jacob. 2010. Crawford M., Marsh D. The driving force : food in human evolution and the future.
Le genou de Lucy. Odile Jacob. 1999. Coppens Y. Pré-textes. L’homme préhistorique en morceaux. Eds Odile Jacob. 2011. Costentin J., Delaveau P. Café, thé, chocolat, les bons effets sur le cerveau et pour le corps. Editions Odile Jacob. 2010. 3 Crawford M., Marsh D. The driving force : food in human evolution and the future.
