About this chapter
This chapter gives a short definition and task description for those parts of the IEC 61850 stan-dard which are needed to do station engineering and process signal routing. A reference to the IEC 61850 parts and clauses is given where needed. The reason for this chapter is to have the common platform about the tasks and the used wording. It can and will not be an introduction to the standard.
1 Station engineering in IEC 61850
The way of engineering and configuring a station according to IEC 61850 standard is described in part 6 of the standard. The title of this part is: “Configuration description language for com-munication in electrical substations related to IEDs”
This chapter contains some explanations about the definitions made by the standard. They may be requested to get a better understanding and as a reference when the different engineering steps made with the tools PCM 600/CCT are described. It is expected, recommended that the reader has a general knowledge about the IEC 61850 standard and especially of the parts 6 and 7.
1.1 Engineering process in IEC 61850
Figure 1: IEC 61850–6: Station engineering process
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The standard defines two tools and four file types for station engineering. The above figure shows these tools and files in their relation. In the ideal situation from top down the engineering process and the used tools and files have the following relation:
• System Configurator tool (SC)
- Import a station.SSD file when available. If not continue with the next step - Import the ied.ICD files of the products which will be used
- When no station.SSD file is available, configure the primary equipment (Busbar, Transformer, Apparatus, connections etc. to voltage level and bays.
Make a single line diagram of the station. Remark: This step and the next one is not direct needed to do signal engineering in a station for IEC 61850 based communication. A minimum configuration of the plant structure is requested only.
- Place the Logical nodes to the primary equipment they belong to within a bay.
- Configure the communication with their subnetworks.
- Place the physical IEDs in the communication subnetwork and define the ac-cess points per IED
- Place the IEDs with their Logical devices and Logical nodes in the plant structure
- Do signal engineering. Configure DataSets, Control Blocks and link the communication path between server and clients or between servers (GOOSE).
- Export the complete station configuration in the station.SSD file for further use by the various IED Configurator tools
• IED Configurator tool (IC)
- Import the station.SCD file and extract the information valid and used for each used IED.
- Do additional engineering steps when necessary (vendor specific) - Check for received GOOSE messages and do GOOSE signal marshalling
when necessary
- Prepare the ied.CID file and download the file to the IED
- Precondition in this case: The IED is fully engineered to its function in the project. The ied.ICD file was exported with the complete configuration to the SC tool as described above.
• SSD file = System Specification Description file
- This file describes the single line diagram of the substation and the required Logical nodes. It is expected that the utility is able to support the project with such a file.
• ICD file = IED Capability Description file
- This file describes the full capability in Logical nodes and Logical devices of an IED without any relation to the substation and communication organiza-tion. This is the basis for the SC tool about the volume and capability of the selected IED for signal engineering. This file is possible in two principle variants. First it is a general description without a direct project specific con-figuration and programming. This file describes the general capability. Sec-ond it is the ied.ICD file of the full engineered IED according to project
specification and requirements. In this case the volume of available Logical nodes and therefore signals will be the final one. Which variant is used must be clarified within the project.
• SCD file = Station Configuration Description file
- An SCD file is given when the substation and communication section con-tains configured values. This file concon-tains all IEDs, a communication config-uration section and a substation section.
• CID file = Configured IED Description file
- The CID file contents is not part of the standard. It is vendor specific. It should contain the result of the engineering process on IED and station level.
• As it can be seen there are various possibilities in which order the engineering will be done. Especially the bay level IED for protection and control may need in most cases project specific adaptations and configuration, which has influence on the volume of used Logical nodes and therefore data objects. The concept allows to re-import an extended ied.ICD file and to add or delete signals in the station.
The tools have to support this concept.
2 Designation model of IEC 61850
The description in the following sections will reference to an example station. This is relevant for the description of the object designation and signal addressing requirements.
A substation of any size consists of buildings, a lot of primary equipment, substation control equipment and a lot more. Each item has a name and will be identified by explaining to which part it belongs to. The rules will differ from country to country and by each utility.
Figure 2: Example station for object designation
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=-WH1 (station bus, optical)
=- WA1
The IEC 61850 standard is based on the hierarchical addressing and designation model in a sta-tion. It follows in this way the structure of the substation equipment independent of IED struc-ture and organization.
This designation and addressing model is also visible in the IEC 61850 telegrams because the address is presented in MMS as an ASCII string, so the address can be seen directly in a readable form.
The above figure shows a virtual example station. The identification is based on the IEC 61346 concepts. Reasons to use the IEC 61346 model:
• the IEC 61346 has the task to define structuring principles and reference desig-nations.
• the standard is international in the same way as IEC 61850 is
• the standard has made a concept which can be used in all industrial systems in-dependent of a language, project etc.
• the standard use only single characters per level which makes the total designa-tion very short and therefore saves bytes to be transmitted.
• by using this designation model in IEC 61850 it allows to use an easy project in-dependent identification.
The designation of a Logical node and its signals (DO) is needed to identify it to the primary object etc. The hierarchical order in a substation is the path to identify the LN.
Figure 3: IEC 61850: Object identification model based on IEC 61346 (FuncName)
The designation path to get the position of the circuit breaker as an example would be:
• DeStat => E1 => Q1 => LD1 => QA1 => XCBR1 => Pos => stVal
• in IEC 61850 = DeStat.E1Q1/LD1QA1XCBR1.Pos.stVal and for the operate signal of the time overcurrent protection:
• DeStat => E1 => Q1 => LD2 => P => PTOC => Op
• in IEC 61850 = DeStat.E1Q1/LD2P.PTOC.Op
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The above model of designation identification is possible when the station configuration is based on the “FuncName” method in IED 61850. This is specified in the Header section of the SCL file. The standard identifies these object or signal designations as the technical key. The standard recommends to use the IEC 61346 based designation model, but it is not a must. But a similar naming structure is requested when an existing identification concept has to be used.
2.1 IEC 61346 designation model used for IEC 61850
Basics of the IEC 61346 standard:
• three different views are defined - the functional view (identified by =) - the product view (identified by -) - the location view (identified by +)
• to separate two levels in a row the character “.” is used. It is allowed to leave the
“.” out, when the last character is a digit and the first character of the next level is a letter.
• the transition from one view to another is visible when both identification signs are used in the sequence from > to. E.g. =-QA1 indicates this is a transition from functional view “=” to product view “-”. The functional view is here the bay Q1 and the product is the circuit breaker QA1.
• each level is represented by one character. A second character is used to identify a type within a level, e.g. QB = HV switching equipment of type disconnector, QA = circuit breaker and QC = grounding disconnectors.
The IEC 61346 defines the rules etc. and gives explanations how to organize the structure and the use of the characters but it does not give a model for each industrial area. This has to be done by working groups.
For the substations for electrical energy distribution the German community of interest “IG EVU” has taken this task. Member of the IG EVU are beside others the main vendors and the main utilities of Germany. The papers are available and free of charge via Internet “www.ige-vu.de”. The documents can be found on the page “Veröffentlichungen”.
The following extracts of the designation trees shows the position of the used elements.
Figure 4: Extracts of IEC 61346 designation trees
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B Switchgear > 420 kV AA Central control system C Switchgear 380 ... 420 kV
D Switchgear 220 ... 380 kV E Switchgear 110 ... 220 kV F Switchgear 60 ... 110 kV G Switchgear 45 ... 60 kV
Function Level 2 and 3
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HSignal and control cable, data bus (optical)
Products Level 3 and 4
3 Substation Configuration description Language (SCL)
The SCL language is based on XML.
It is of course not needed to know the XML file in its details and do any step which requests XML knowledge, but the organization of the information within the SCL files (ied.ICD and/or station.SCD) might be of interest. Especially to know where the engineering additions like DataSets and Control Blocks belongs to.
The SCL XML file is defined in five sections or descriptions, which are specified in IEC 61850–6 clause 9. These sections are:
• the Header
• the Substation description (section)
• the Communication description (section)
• the IED description (section)
• the Data Type Templates
The first two sections can be seen as tasks to organize the IEDs within the substation and to es-tablish the communication. These tasks are done by the PCM 600 tool. The Logical nodes as part of the IED are logically linked to the substation section by PCM 600. The signal engineering task and routing of the signals is the task of the CCT tool. Its precondition is that PCM 600 has done the complete organization on the two sections substation and communication.
The DataSets and Control Blocks configured by the CCT tool are located in the IED section be-cause they are logically defined as part of the Logical nodes (see IEC 61850–7–2 clause 9). The CCT needs the correct configured communication section when it comes to GOOSE engineer-ing.
The Data type templates section is requested to give the correct content description of each Log-ical node type to all user of the information. These are the clients. Each IED and vendor may have/has its own Logical node type definitions.
Figure 5: IEC 61850: Principle structure of the SCL XML file
Figure 5 shows a principle structure of the SCL XML file with its five sections. The arrows show the link between the different sections given when an IED is integrated in the substation struc-ture and/or in the communication strucstruc-ture. All available Logical nodes of an IED are linked to the substation section.
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Id ToolId Nam eStructure
IED Nam e AccessPoint Address GSE
IED Nam e AccessPoint Address GSE
Services
A reference to the GoCB is included in the communication section when the GoCB is config-ured.
The above graphical presentation of the XML file is a standard view of XML editors. It gives a better picture about the structure of the XML contents.
3.1 The Substation section
The substation description in IEC 61850–6 clause 9 describes the organization of the primary equipment in a single line diagram on one side. On the other side it describes the used LNs be-longing to a bay. The second part is of interest for the signal engineering.
In part 6 clause 8.4 of the standard the object and signal designation rules are described. The identification for the signals are therefore also used in the telegrams defined in IEC 61850–8–1 is named “Technical key”. The technical key is used within the SCL description to identify and reference objects. See chapter 2, section 1 "Station engineering in IEC 61850" about the concept based on IEC 61346. PCM 600 generates an “SCL Technical key” independent of the naming given by the project. The PCM 600 generated technical key is based on the definitions given in IEC 61346 and for electrical substations. When a project is using its own naming model this will be used by the SCL description as technical key. PCM 600 allows to select the version which should be used in the SCL files when exporting a station.SCD file.
Signal identification in the communication system
The signal identification rules used by IEC 61850 are described in part 7–2 clause 19.2. and used in part 6 clause 8.4.2
The signal designation consists of four parts:
1. a user defined part identifying the Logical device LD in the process (LDName) 2. a function related part to distinguish several LNs of the same class within the
same LD/IED (LN-Prefix)
3. the standardized LN class name and the LN instance number, which distinguishes several LNs of the same class and prefix within the same LD/IED
4. a signal identification inside a LN consisting of data and attribute name as de-fined in IEC 61850–7–3 and IEC 61850–7–4
Figure 6: Elements of the signal identification as defined in IEC 61850–7–2
The above figure is taken from the standard IEC 61850–6 (figure 5).
The standard defines two options how to use part 1 and part 2 above:
1. Function related naming
• identified in the SCL header with NameStructure = FuncName 2. Product related naming
• identified in the SCL header with NameStructure = IEDName Within one SCL project only one option can be used.
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Function related naming
Figure 7: IEC 61850–6: Function related naming
The part 1 = LDName of signal identification is build out of the objects Substation (1), Voltage level (2), bay (3) and the LD (4). The LN Prefix in this case is an additional element which be-longs to the LDName part. It identifies the equipment or sub-equipment object in the primary
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LN Prefix LN class LN instance no
Substation section IED section Substation section
1 2 3 4 5
Signal naming using functional naming
Elements of signal identification IEC 61850-7-2
6
structure. The typical example is the circuit breaker QA1, when the LN classes XCBR, CSWI and CILO are used. It has to be regarded that in this model the IED is not included and the nam-ing is based in the process objects only.
The LNName is in this option the LN class and the LN instance (6) only.
Product related naming
Figure 8: IEC 61850–6: Product related naming
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LN Prefix LN class LN instance no
IED section
Signal naming using product naming
Elements of signal identification IEC 61850-7-2
IED 4 IED 5 IED y
The LDName part is build in this option out of the objects IED (A) and LD (B). The link to the primary process is not given in this model.
The LNName is in this option the LN Prefix, the LN class and the LN instance no (C).
The LN prefix allows in this model to identify several versions of a LN class. For example the eight different versions the LN class PDIF.
The link between the IED and the primary process (Substation (1), Voltage level (2), bay (3)) is given in the substation section of the station.SCD file but not in the signal identification in the telegram. The project may decide how to deal with this matter. The IED name may be extended with a short form of the three missing levels. The IEDName must be unique in this designation model.
Remark:
The standard defines the maximum length for the signal naming and for identification parts to 32 ASCII characters each. This has to be regarded for the object identification for part 1 to part 4 (see figure 6). In addition it might be possible that client IEDs have additional restrictions which have to be taken into account.
Most vendor have to use the LN Prefix to identify their versions etc. Therefore the product re-lated naming model (IEDName) will be used.
3.2 The communication section
The organization of the physical IEDs to the communication network is independent of the sub-station structure. The IEC 61850 standard defines the communication network with no relation to an existing media and protocol. The first mapping to an existing media and protocol is done in IEC 61850–8–1 with:
• Ethernet as medium
• MMS (Manufacturing Message Specification) protocol as defined in ISO 9506–1 and IOS 9506–2.
The IEC 61850 standard describes in part 7–2 the Abstract Communication Service Interface (ACSI) in a media and protocol independent form. Part 8–1 specifies the mapping of this ACSI to the existing MMS.
The communication section in the SCL file describes the minimum of what is needed to identify how information is routed between the IEDs in a project. This is.
• the used subnetworks
• the IEDs connected to the different subnetworks
• the access points per IED to the subnetworks
• the address
• the IP address of the LAN network is as an exception also part of the address el-ements
• and, extended during signal engineering and routing, the link to the GoCB mes-sage in transmission direction.
Figure 9: IEC 61850–6: Communication network
Figure 9 shows the contents of the communication section. Additional information about the server etc. is part of the IED.
The link to the IEDs is done by PCM 600 when the IED is placed and the link to the subnetwork established. The list of “Connected AP” in the communication section of the SCL file includes all IEDs with their APName.
A station as shown in figure 3 the station uses two voltage levels with a set of bays and IEDs per bay. The communication network can be done in several ways for this station. The most typical variants are shown in figure 10.
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Figure 10: Communication section: Possible network configuration examples
Both variants fulfil the requirements and performance. Variant 2 may be used, when the avail-ability question is discussed. In this case only one voltage level of the station is lost when a sub-network fails. The client IEDs must be able to handle two access points.
3.3 The IED section
The IED section describes the complete IED as it is needed for IEC 61850 communication and signal engineering. The Data Type Template part of an IED may be seen as part of the IED, even when separated in its own section. The ied.ICD files includes the description of the LNs, their Data Type Templates and the used/supported services. The structure of the IED section follows the definitions made in the IEC 61850 standard.
There are two basic IED types which are used:
There are two basic IED types which are used: