61850-5©1EC:2001 26 57/526/CDV 9.2 The need for a formal system description Where the data potentially coming from (sending LN)and going to (receiving LN),i.e.the static structure of the communication system has to be engineered or negotiated during the set-up phase of the system.Opening and closing communication channels dynamically at run time will refer always to the given static structure.To control the free allocation and to create interoperable systems.a strong formal device and system description for communication engineering shall be provided.Such a description (substation configuration language independent from supplier)is defined in part 6 of this standard(IEC 61850-6). 9.3 Requirements for logical node behavior Each receiving LN shall know what data is needed for performing its task;i.e.it shall be able to check if the delivered data are complete and valid having the proper quality.In real-time systems like substation automation,the most important validity criterion is the age of the data. The sending LN may set most quality attributes.The decision if data are"old"is the genuine task of the receiving LN.Missing or incomplete information is covered since in this case no data with an acceptable age are available.Therefore,the requirements for communication providing interoperability between distributed LNs are reduced to the standardization of the data to be available or needed and the assignment of validity (quality)attributes in an appropriate data model as defined in part 7 of this standard(IEC 61850-7-x). The requirements mentioned above imply that the sending LN is also the source of the primary data,i.e.it keeps the most actual values of these data,and the receiving LN is processing these data for some related functionality.In case of mirrored data (data base image of the process,proxy server,etc.)these mirrored data shall be kept as actual("valid") as needed by the function using these data. In case of corrupted or lost data,the receiving LN can not operate in a normal way but may be in a degraded mode.Therefore,the behavior of the LN both in the normal and degraded mode has to be well defined but the degradation behavior of the function has to be designed individually depending on the function and is beyond the scope of this standard.Also the other LNs of the distributed function and the system supervision shall be informed about this degradation by a standardized message or proper data quality attributes to take the actions requested.If there is e.g.enough time,a request for sending valid data could be sent out also (retry).The detailed sequential behavior of the distributed functions cannot be standardized at all Examples of data based complex interoperability are the different interlocking algorithms(e.g. Boolean or topology based interlocking)which can be performed with the same data set(the position indications of the switchgear). Since the logical node concept covers essential requirements in a consistent and comprehensive way.this concept itself is seen as a requirement,which shall be used in the detailed modeling given in part 7 of this standard(IEC 61850-7). 9.4 Examples for decomposition of common functions into logical nodes In Fig.4,there are examples of common functions given Synchronized circuit breaker switching Distance protection Overcurrent protection The functions are decomposed into logical nodes listed in the figure,the allocated physical devices are described by numbers
61850-5 IEC:2001 57/526/CDV 26 9.2 The need for a formal system description Where the data potentially coming from (sending LN) and going to (receiving LN), i.e. the static structure of the communication system has to be engineered or negotiated during the set-up phase of the system. Opening and closing communication channels dynamically at run time will refer always to the given static structure. To control the free allocation and to create interoperable systems, a strong formal device and system description for communication engineering shall be provided. Such a description (substation configuration language independent from supplier) is defined in part 6 of this standard (IEC 61850-6). 9.3 Requirements for logical node behavior Each receiving LN shall know what data is needed for performing its task; i.e. it shall be able to check if the delivered data are complete and valid having the proper quality. In real-time systems like substation automation, the most important validity criterion is the age of the data. The sending LN may set most quality attributes. The decision if data are “old” is the genuine task of the receiving LN. Missing or incomplete information is covered since in this case no data with an acceptable age are available. Therefore, the requirements for communication providing interoperability between distributed LNs are reduced to the standardization of the data to be available or needed and the assignment of validity (quality) attributes in an appropriate data model as defined in part 7 of this standard (IEC 61850-7-x). The requirements mentioned above imply that the sending LN is also the source of the primary data, i.e. it keeps the most actual values of these data, and the receiving LN is processing these data for some related functionality. In case of mirrored data (data base image of the process, proxy server, etc.) these mirrored data shall be kept as actual (“valid”) as needed by the function using these data. In case of corrupted or lost data, the receiving LN can not operate in a normal way but may be in a degraded mode. Therefore, the behavior of the LN both in the normal and degraded mode has to be well defined but the degradation behavior of the function has to be designed individually depending on the function and is beyond the scope of this standard. Also the other LNs of the distributed function and the system supervision shall be informed about this degradation by a standardized message or proper data quality attributes to take the actions requested. If there is e.g. enough time, a request for sending valid data could be sent out also (retry). The detailed sequential behavior of the distributed functions cannot be standardized at all. Examples of data based complex interoperability are the different interlocking algorithms (e.g. Boolean or topology based interlocking) which can be performed with the same data set (the position indications of the switchgear). Since the logical node concept covers essential requirements in a consistent and comprehensive way, this concept itself is seen as a requirement, which shall be used in the detailed modeling given in part 7 of this standard (IEC 61850-7). 9.4 Examples for decomposition of common functions into logical nodes In Fig. 4, there are examples of common functions given • Synchronized circuit breaker switching • Distance protection • Overcurrent protection. The functions are decomposed into logical nodes listed in the figure, the allocated physical devices are described by numbers
61850-5©1EC:2001 27 571526/CDV 1.Station computer 2.Synchronized switching device 3.Distance protection unit with integrated Overcurrent function 4.Bay control unit 5.Current instrument transformer 6.Voltage instrument transformer 7.Busbar voltage instrument transformer tio The logical node "device"(LLNO)as contained in any physical device is not shown Functions- Logical Synchronised Distance Overcurrent Nodes CB switching protection protection HMI X X X Sy.Switch. X 国因 Dist.Prot. X O/C Prot. Physical D Breaker X X X Bay CT X X 回 evices Bay VT X X BB VT X Fig.4-Examples of the application of the logical node concept(explanation see text)
61850-5 IEC:2001 57/526/CDV 27 1. Station computer 2. Synchronized switching device 3. Distance protection unit with integrated Overcurrent function 4. Bay control unit 5. Current instrument transformer 6. Voltage instrument transformer 7. Busbar voltage instrument transformer The logical node “device” (LLN0) as contained in any physical device is not shown. HMI Sy.Switch. Dist.Prot. O/C Prot. Breaker Bay CT Bay VT BB VT Logical Nodes X X Distance protection X X X X Synchronised CB switching X X X X X Overcurrent protection X X X [--------------------Functions----------------] [---------Physical Devices-------] 1 2 3 4 5 6 7 Fig. 4 – Examples of the application of the logical node concept (explanation see text)
61850-5©1EC:2001 28 57/526/CDV 9.5 The PICOM concept PICOMs introduced by CIGRE WG34.03 are used to describe the information exchanged between LNs.The components or attributes of a PICOM are: Data meaning the content of the information and its identification as needed by the functions (semantics) Type describing the structure of the data,i.e.if it's an analog or a binary value,if it's a single value or a set of data,etc. Performance meaning the permissible transmission time (defined by performance class), the data integrity and the method or cause of transmission (e.g.periodic,event driven,on request). Logical connection containing the logical source (sending logical node)and the logical sink(destination or receiving logical node) NOTE:PICOMs describe exchanged information("content")and communication requirements ("attributes").The "bits on the wire"are found in the mappings,i.e.in the parts IEC 61850-8 and IEC 61850-9. 9.6 ATTRIBUTES OF PICOMS There are three types of attributes defined by their purpose 9.6.1 PICOM attributes to be covered by any message Value value of the information itself if applicable Name for identification of the data Source: the LN where the signal comes from Sink: the LN where the signal goes to Time tag: absolute time to identify the age of the data if applicable Priority of transm.:to be used for -LN input queues (if more than one) -LN input and output(re-transmission order)in case of intermediate LNs Time requirements cycle time or overall transfer time to check the validity with help of the time tag NOTE:To specify the communication requirements,pairs of sources and sinks have to be identified.Sometimes multicast and broadcast messages maybe more convenient for the communication but this is a matter of implementation. 9.6.2 PICOM attributes to be covered at configuration time only Value for transmission(see above):test or default value if applicable Attributes for transmission(see above) Accuracy: classes or values Tag information: if time tagged or not(most data will be time tagged for validation) Type: analog,binary,file,etc Kind: alarm,event,status,command,etc. Importance high,normal,low
61850-5 IEC:2001 57/526/CDV 28 9.5 The PICOM concept PICOMs introduced by CIGRE WG34.03 are used to describe the information exchanged between LNs. The components or attributes of a PICOM are: • Data meaning the content of the information and its identification as needed by the functions (semantics) • Type describing the structure of the data, i.e. if it’s an analog or a binary value, if it’s a single value or a set of data, etc. • Performance meaning the permissible transmission time (defined by performance class), the data integrity and the method or cause of transmission (e.g. periodic, event driven, on request). • Logical connection containing the logical source (sending logical node) and the logical sink (destination or receiving logical node) NOTE: PICOMs describe exchanged information (“content”) and communication requirements (“attributes”). The “bits on the wire” are found in the mappings, i.e. in the parts IEC 61850-8 and IEC 61850-9. 9.6 ATTRIBUTES OF PICOMS There are three types of attributes defined by their purpose. 9.6.1 PICOM attributes to be covered by any message • Value : value of the information itself if applicable • Name : for identification of the data • Source: the LN where the signal comes from • Sink : the LN where the signal goes to • Time tag : absolute time to identify the age of the data if applicable • Priority of transm. : to be used for - LN input queues (if more than one) - LN input and output (re-transmission order) in case of intermediate LNs • Time requirements :cycle time or overall transfer time to check the validity with help of the time tag NOTE: To specify the communication requirements, pairs of sources and sinks have to be identified. Sometimes, multicast and broadcast messages maybe more convenient for the communication but this is a matter of implementation. 9.6.2 PICOM attributes to be covered at configuration time only • Value for transmission (see above) : test or default value if applicable • Attributes for transmission (see above) • Accuracy : classes or values • Tag information : if time tagged or not (most data will be time tagged for validation) • Type: analog, binary, file, etc. • Kind: alarm, event, status, command, etc. • Importance : high, normal, low
61850-5©1EC:2001 29 571526/CDV ·Data integrity: the importance of the transmitted information for checks and re- transmissions(IEC class 2 is applicable only and,therefore,no transmission of this attribute is needed) 9.6.3 PICOM attributes to be used for data flow calculations only Value for transmission/configuration(see above):test or default value if applicable Attributes for transmission/configuration(see above) Format: value type of the signal:I,Ul,R,B,BS,BCD,etc. ·Length: the length:i bit,i byte,k word State of operation:reference to scenarios NOTE:Format and length are a matter of implementation and not a requirement.For data flow calculations assumptions about these two attributes have to be made. not for reproc
61850-5 IEC:2001 57/526/CDV 29 • Data integrity : the importance of the transmitted information for checks and retransmissions (IEC class 2 is applicable only and, therefore, no transmission of this attribute is needed) 9.6.3 PICOM attributes to be used for data flow calculations only • Value for transmission/configuration (see above) : test or default value if applicable • Attributes for transmission/configuration (see above) • Format : value type of the signal : I, UI, R, B, BS, BCD, etc. • Length : the length : i bit, j byte, k word • State of operation : reference to scenarios NOTE: Format and length are a matter of implementation and not a requirement. For data flow calculations, assumptions about these two attributes have to be made.
61850-5©1EC:2001 30 57/526/CDV 10 LIST OF LOGICAL NODES Most of the functions consist of three logical nodes in minimum,i.e.the LN with the core functionality itself,the process interface LN and the HMI (human-machine interface)LN meaning human access to the function.If there is no process bus,the LNs of the remote process interface are allocated to another physical device (in the example shown in Fig.5 the physical "Protection device). If we call a function e.g."protection function"we refer mostly to its core functionality only. Therefore,the function list given e.g.in the report of CIGRE 34.03 is a list of logical nodes according to our definitions. Protection Station function computer HMI XCBR LC2 Protection LC1 TCTR device (relay) 1F4,5 Remote process interface Fig.5-Protection function consisting of 3 logical nodes(IHMI,P..=protection,XCBR=circuit breaker to be tripped)residing in 3 physical devices(Station computer,Protection device and Remote process interface).Abbreviations for LN designation same as introduced in the tables of clause 10 Table columns Logical Node displays a short description of the task of the LN for common understanding. For full understanding the data to be exchanged have to be considered also. 61850 means abbreviations/acronyms with a systematic syntax used by IEC 61850 IEEE means device function numbers and contact designations used in IEEE Std C37.2- 1996 Electric Power System Device Function Numbers and Contact Designation Description or Comments displays the description of the IEEE device number if applicable or/and other descriptive text Note that the reference to the lEEE device number means not the related devices but its core functionality only(see definition of LN and Fig.5)in the context of this standard
61850-5 IEC:2001 57/526/CDV 30 10 LIST OF LOGICAL NODES Most of the functions consist of three logical nodes in minimum, i.e. the LN with the core functionality itself, the process interface LN and the HMI (human-machine interface) LN meaning human access to the function. If there is no process bus, the LNs of the remote process interface are allocated to another physical device (in the example shown in Fig. 5 the physical “Protection device”). If we call a function e.g. “protection function” we refer mostly to its core functionality only. Therefore, the function list given e.g. in the report of CIGRE 34.03 is a list of logical nodes according to our definitions. Fig. 5 - Protection function consisting of 3 logical nodes (IHMI, P..=protection, XCBR=circuit breaker to be tripped) residing in 3 physical devices (Station computer, Protection device and Remote process interface). Abbreviations for LN designation same as introduced in the tables of clause 10 Table columns Logical Node displays a short description of the task of the LN for common understanding. For full understanding the data to be exchanged have to be considered also. 61850 means abbreviations/acronyms with a systematic syntax used by IEC 61850 IEEE means device function numbers and contact designations used in IEEE Std C37.2- 1996 Electric Power System Device Function Numbers and Contact Designation Description or Comments displays the description of the IEEE device number if applicable or/and other descriptive text Note that the reference to the IEEE device number means not the related devices but its core functionality only (see definition of LN and Fig. 5) in the context of this standard. Station computer Protection function IF 4,5 IF 1 LC1 HMI XCBR TCTR Remote process interface P.. LC2 Protection device (relay)