How to Use IEC 61850 in Protection and Automation

0508-095Mep222 7/12/05 16:51 Page 11 REPORT SC B5

How to use IEC 61850 in Klaus-Peter BRAND (Switzerland),2 protection and automation Christoph BRUNNER 3 from Ivan de MESMAEKER1 (Switzerland), Ivan de MESMAEKER (Switzerland)

Introduction decentralized ones as used in fully developed substation automation system The use of numerical technology in Pro- • Be future-proof, i.e. to cope with the fast tection and Automation has provided multi- development in communication technology in functional equipment with serial communica- the slow evolving application domain of power tion. The introduction of serial communication systems. some years ago resulted in the use of proprietary protocols for the communication of con- These are very ambitious goals because all trol and protection IEDs (Intelligent Electronic functionality needed in substations had to be Devices) installed in the substation. examined with respect to their communication Of course, some IEC standards have been behavior and requirements. issued: an important one standardized the communication between substation and The resulting standard IEC 61850 [4] is now remote control centre (IEC 60870-5-101/104 finalized but a joint group of users, editors and [1], [2]), another one defined the protocol for IEC working group members is collecting the communication with protection equip- experience from the use of the standard, iden- ment (IEC 60870-5-103 [3]). These two have tifying points where clarification is needed and been very well accepted but especially the areas where extensions are requested. The IEC 60870-5-103 has shown its limited result will be short-term amendments and design: designed as master-slave protocol long-term revisions. A challenge is the com- restricted to some protection functions and prehensive range of the standard covering a relatively little number of standardized functional aspects, communication aspects, numbered data. engineering aspects and conformity tests. For substation automation systems, first projects Users request an open protocol for all func- are now realized and the first experiences will tions like protection, control and monitoring be reported very soon. at least inside substations (see e.g. in [11]). Open means to have the possibility to make Taking into consideration all the different extension without being dependant on the dedicated activities related to protection and manufacturer having delivered the previous control inside substations it is also very impor- parts of the substation equipment. This means tant to establish a clear understanding, how also that third party equipment should be eas- the tasks have been solved until now and how ily integrated in the system of another manu- they should be solved using the full power of facturer. the standard. The goal of this paper is to facilitate the understanding and to explain how The requested standard has to easy the standard can be applied to exploit all • Cover all communication issues inside the applicable benefits. Therefore, a stepwise func- substation tion-oriented approach is chosen covering • Assure interoperability between the func- • SCADA application in the substation tions existing inside the substation (as pre- • Time critical information exchange liminary condition for interchangeability) • Connection of the primary process • Support all types of architectures used, • Design, test and commission e.g. centralized ones similar to RTUs and • Maintenance and extension

1. I. de MESMAEKER, Chairman of SC B5 2. Klaus-Peter BRAND, IEC expert 3. Christoph BRUNNER, IEC expert

No. 222 - October 2005 ELECTRA 11 0508-095Mep222 7/12/05 16:51 Page 12 SC REPORT B5 Finally, an outlook is given to the future is the process or bay level IED, which provides ongoing and proposed work based on the all data to the client at station or any remote standard IEC 61850 and leading to seamless level. The data are provided on request by the utility communication architecture. server or automatically by a report from the server issued if certain conditions are fulfilled. How to use IEC 61850 for SCADA The client is mostly a computer representing application in substations the operator’s work place. The client can send commands to the server for changing data in Tasks the server to: Supervisory control and data acquisition • Issue commands for the operation of to (SCADA) is one of the basic tasks of a substa- the switchgear tion automation system. This comprises: • Modify the behavior of the server through • Local and remote operation of the the change of internal data (e.g. change of switchgear and other high voltage equipment parameter sets, analog set-points, enabling or • Acquisition of switchgear information and disabling functions) power system measurands • Handling of events and alarms. In a client-server communication, the client controls the data exchange. Therefore, client- The SCADA application is related to human server communication is very flexible in terms operation of the network and is performed by of the data to be transmitted. Compared to a local or remote operator. The data commu- a master slave system, the client-server con- nication for this application is directed verti- cept allows the implementation of multiple cally, i.e. from a higher hierarchical control clients in the same system. (Figure 1; e.g. both level down to a lower one (commands of any the gateway and the HMI are clients). Client- kind from the operators place) or reverse server communication relies on the full seven (binary indications like breakers or isolators layer stack using a confirmed transmission layer position, measurands from instrument trans- and is, as consequence, very reliable but rel- formers and other sensors, events, alarms) as atively time consuming. Therefore, the client- can be seen from Figure 1. It allows to oper- server communication is not suited for time- ate and to supervise the power system. critical data transmission but very well for the communication with an operator having a response time of the order of 1 s.

IEC 61850 not only specifies the method of the data transfer. It defines as well the process data of the servers. For that purpose, IEC 61850 uses an object-oriented approach with Logical Nodes (LN) as core objects (see [5], [7]). A logical node is a functional grouping of data and represents the smallest function, which may be implemented independently in devices. Examples are all data of a circuit breaker contained in the Logical Node XCBR or all data of a timed overcurrent protection contained in the Logical Node PTOC. There- fore, the substation or protection engineer Figure 1: Vertical communication in the substation identifies easily the objects he knows from automation system with hardwired process interface his daily work.

Model As outlined in Figure 2 all the Logical For this vertical relationship IEC 61850 is Nodes have data, and all the data have using the client - server concept [5]. The server attributes. For example, the LN class

12 ELECTRA N° 222 - Octobre 2005 0508-095Mep222 7/12/05 16:51 Page 13 REPORT SC B5 XCBR (Q0_XCBR) has a data called Pos, with To access the data, several services are one attribute stVal, which indicates the posi- standardized as part of the client-server con- tion (values according the common double cept. Besides the basic services to access the point indication: off, on, intermediate-state, data model (individual read or write of data), bad-state) and another attribute ctlVal for the more elaborated services are defined. As an opening and closing command (values: off, on). example, for the SCADA application, event The Logical Nodes, the data and the attributes driven transmission of data is essential. In IEC including their names and semantic interpre- 61850, the report service is defined for that pur- tation are defined by the standard. pose. The report service is not accessing individual data, but group of data called dataset. Logical Nodes are grouped in Logical The details of the event driven transmission are Devices. Example: Logical Device Tampa_Pro- defined in the report configuration block. An tection for a comprehensive two zone distance event causing a transmission may be a change protection using one Logical Node PDIS per of a binary value, the crossing of a predefined zone (PDIS1 and PDIS2 in Figure 2). By alarm limit or the expiration of a cycle time. enabling or disabling a Logical Device, it is pos- Based on the report configuration block and sible to enable and disable the contained the related dataset, reports are sent to the group of Logical Nodes together. client. Including the time tag of the event as part of the dataset, event lists can be created. Logical Devices are implemented in phys- For that purpose, the IED is typically synchro- ical devices (IEDs). There is some actual infor- nized with accuracy in the order of 1 ms. mation needed not only about the Logical Nodes and Logical Devices but also about the Applications complete IED like the status of the common A typical application of SCADA is the cre- power supply. This information is modeled in ation of alarm lists and event lists. Today, the the Logical Node LPHD, which has to be pro- data content of the alarm lists and event lists vided in each Logical Device (see Figure 2). is specified through signal lists. With IEC 61850, datasets used together with the report service can be used for that purpose. As an example, a utility may specify a dataset per IED that contains all data for the alarm list.

The NCC gateway provides the interface from the NCC to the substation. It has two basic tasks: • Protocol and data conversion • Data collection For the data collection, the NCC gateway is a client in the IEC 61850 based substation automation system. The data is typically col- Figure 2: lected using the report model. The dataset Hierarchical data model and naming used in that case corresponds to the traditional signal list specifying the information from the An important aspect of a data model is the substation to be transmitted to the NCC. unambiguous identification of the data. Accord- ing to IEC 61850, the name is created by the How to use IEC 61850 for time concatenation of the individual elements of the critical information exchange hierarchical data model: logical device, logical node instance, data and data attribute. Exam- Task ple for the status of the breaker Q0 in the bay There are several automated functions in Tampa: Tampa_Control/Q0_XCBR.pos.stVal the substation automation system, which (Figure 2). require a time critical exchange of binary

No. 222 - October 2005 ELECTRA 13 0508-095Mep222 7/12/05 16:51 Page 14 SC REPORT B5 information between functions located within Model the same bay or in different bays. Examples: The concept of logical nodes has been • Exchange between line protection and introduced in clause 2.2. As an example, for autorecloser the information exchange between the pro- • Exchange between bays for breaker failure tection function and the breaker failure func- • Exchange between bays for station inter- tion, the following logical nodes are involved: locking • PTRC (Protection Trip Conditioning) rep- Typically, these functions are not using resenting the logic in a protection device that human interaction and are time critical. They creates the binary outputs (start and trip out- are time critical because they are safety criti- put of e.g. the line protection device) cal. The maximal accepted communication • RBRF representing the protection Related delay is in the range of several milliseconds [7]. function Breaker Failure function

If the functions exchanging the information The information exchange between these are located in different IED’s, the information logical nodes is also modeled as data. The data exchange may be done using copper wiring is part of the logical node that is the source of with contacts and auxiliary relays or using serial the information exchange. As an example, the communication. This information exchange logical node PTRC has a data Tr with an is a horizontal communication between devices attribute general representing the trip output at the same hierarchical level (Figure 3). of the protection device for a general trip. That signal is not only used to operate the breaker, Theoretically, the information exchange but it is used as well to trigger e.g. the breaker could take place using the client-server com- failure function (see Figure 4 and Figure 5). munication. However, client-server communication is using the full seven-layer stack and is For the exchange of this type of (binary) therefore relatively time consuming. An appro- information over serial communication, IEC priate communication concept used is a pub- 61850 introduces a specific information lisher-subscriber communication. The publisher exchange service called GOOSE (Generic is distributing the information over the com- Object Oriented Substation Event) based on munication network; the subscriber may receive the publisher-subscriber concept. The con- the information according his needs. In IEC tent of a GOOSE message is defined with a 61850 publisher-subscriber communication is dataset (similar like for the report model not using confirmed services and is therefore described above). The GOOSE message is transmitted over a reduced communication sent as a multicast message over the com- stack resulting in a very short transmission time. munication network. That means that multiple devices can receive the message and retrieve the information required from the message. The communication service is not confirmed; instead, the message is repeated several times.

In the example of the breaker failure function a GOOSE message is configured in the protection device that contains at least the data attribute PTRC.Tr.general. As soon as PTRC.Tr.general changes its value to TRUE, the GOOSE message is sent. The device performing the breakure failure function is receiving this message and detects that PTRC.Tr.general has changed its value to Figure 3: Horizontal communication in the substation TRUE. Another GOOSE message is sent when automation system with hardwired process interface the value changes back to FALSE.

14 ELECTRA N° 222 - Octobre 2005 0508-095Mep222 7/12/05 16:51 Page 15 REPORT SC B5 Applications the breaker failure function has already been Basically, there are two types of applica- used as example to explain the model in the tion, depending if the exchange of informa- clause 3.2. In case the concerned breaker does tion is between devices inside the bay or not open, the breaker failure function may between devices placed in different bays. retrip (RBRF.OpIn) and, without success send a trip to all surrounding breakers. This is mod- Exchange of information inside the bay: eled with the data RBRF.OpEx. A typical example is the exchange of information between Logical Device “Distance Pro- tection” containing instances of LN PDIS per zone and the LN PTRC ( and the Logical Device “Recloser” containing the LN RREC (, in case these both functions are installed in separate devices (Figure 4).

The LD “Distance Protection” sends information to the LD “Recloser”: start of starting elements in LN PTRC (PTRC.Str) and trip in LN PTRC (PTRC.Op). Based on these information and depending on the settings (single pole recloser or three pole recloser; RREC.TrMod) the recloser function represented by RREC will send information (RREC.TrBeh) to the LD “Dis- tance Protection” in order to enable the expected trip (if one or three phases PTRC.Tr) Figure 5: Breaker failure protection to the breaker. The open command to the in double busbar arrangement breaker is issued by the recloser function (RREC.Op). In Figure 5, the modeling of the breaker failure function in a double bus arrangement Exchange of information between bays: is shown. The breaker failure protection is ini- The information exchange between pro- tiated by trip indications from the LD “Bay Pro- tection device and breaker failure used to start tection” (PTRC.Op). The criterion for

Figure 4: Connection between distance protection and recloser functions

No. 222 - October 2005 ELECTRA 15 0508-095Mep222 7/12/05 16:51 Page 16 SC REPORT B5 breaker failure protection is typically the cur- For the exchange of voltage and current rent (RBRF.FailMod=current) with the setting waveforms using standardized serial commu- RBRF.DetValA. As first step the breaker fail- nication, IEC 61850 defines the service for sam- ure function will issue a retrip to the circuit pled value transmission. All other information breaker (RBRF.OpIn) after a certain time delay exchange is using either the client-server con- (RBRF.SPTrTmms for single pole trip; cept as described in clause 2 for SCADA appli- RBRF.TPTrmms for three pole trip). If the cation and the GOOSE message as described breaker didn’t open before the second time in clause 3 for the time critical communication delay (RBRF.FailTmms) is elapsed, the breaker like e.g. the transmission of a trip signal from failure function will initiate an external trip the protection relay to the circuit breaker. (RBRF.OpEx). This external trip is forwarded according to the busbar image to the sur- Model rounding breakers. While in conventional tech- The concept of logical nodes as functional nology this is implemented with two auxiliary grouping of information has been introduced relays, in IEC 61850 two instances of the LN in clause 2.2. There is a group of logical nodes PTRC are used to model this. A GOOSE mes- that represents the data model of the high volt- sage that contains the data PTRC1.Op and age equipment like PTRC2.Op is distributed to all other bays. • XCBR representing a circuit breaker • XSWI representing any other switching How to use IEC 61850 for process equipment connection • TCTR representing a single phase current transformer Task • TVTR representing a single phase voltage The process connection provides the infor- transformer. mation exchange between the substation automation system and the high voltage equip- The logical nodes XCBR and XSWI include ment: the data Pos with an attribute stVal used to • Voltage and current waveforms retrieve the position information and another • Position and other status one ctVal to execute open and close commands • Open, close and other controls (Figure 2). Additional data is used to model further status information like e.g. the operation The information exchange may be done capability of a circuit breaker (energy stored using copper wiring (e.g. secondary nominal in the drive; e.g. o-c-o). For SCADA applications, value of 100V/5A for voltage and current wave- these logical nodes and their data are accessed forms) or using serial communication (Figure 6). using the client / server based communication.

The logical nodes TVTR and TCTR include the data Vol and Amp. These data represent the sampled value of the voltage and current waveform. For the exchange of voltage and current waveform over a serial communication, a stream of these sampled values needs to be transmitted.

An important aspect while using sampled values of a power system is the phase relationship between the different measured sig- nals, in particular between current and voltage. IEC 61850 is using the concept of synchronized sampling. All units performing sampling are Figure 6: Process connection with serial communication globally synchronized with the required accuracy. The samples are taken all at the

16 ELECTRA N° 222 - Octobre 2005 0508-095Mep222 7/12/05 16:51 Page 17 REPORT SC B5 same time. Each sample is identified with a matical reclosure or manual switch on) a syn- number that provides the time reference. That chrocheck function is useful in order to check approach can deal with variable communica- if both voltages (the one at line side and the tion delays, as they are inevitable when using one at bus side) are nearly identical (amplitude, a network topology for the communication. phase frequency) allowing a switch on without excessive stress. The bus voltage is normally The message with the sampled values is not available per bay but only once per bus typically transmitted as a multicast message zone on which the line will be connected. This – that means the same telegram can be bus zone voltage can be taken from the cor- received by multiple receiving devices. As for responding voltage transformer at the bus and the GOSSE message the content of the mes- introduced to the device where the syn- sage is defined with a dataset. chrocheck function is placed. Using IEC 61850 the samples representing the bus voltage can Applications be sent over the serial link to the synchrocheck A typical application for the process con- function installed in the line bay where the nection is the information transfer between reclosing should take place. instrument transformers, protection devices and circuit breakers. This information transfer is time How to use IEC 61850 for critical. It has a direct impact on the reaction substation automation design time of the protection function. The acceptable transmission delay is in the range of 3 µs [7]. Introduction to SCL Substation automation design is a series of The analog waveform of current and volt- steps from the specification up to the commis- age is transmitted as a stream of samples as sioning of a project specific system. To show described in clause 4.2. In order to fulfill the IEC 61850 is used in this process we have first to requirements for the protection functions, the introduce shortly the Substation Configuration synchronization accuracy for the sampling description Language (SCL) provided by the needs to be in the range of 1…4 µs (e.g. phase standard for this process. SCL was introduced relationship of currents for differential protec- for a comprehensive description of the complete tion, phase relationship between current and SA system supporting the goal interoperability voltage for fault locator and distance protec- of the standard. SCL allows describing the tion). To achieve that synchronization accuracy, • single line diagram, a dedicated synchronization network is cur- • function allocation to the single line dia- rently required. gram, • function allocation to devices, To simplify the synchronization of samples • data as being mandatory and optional from all phases all relevant TCTRs and TVTRs according to IEC 61850 (optional if needed or may be implemented in a common Logical provided), Device called Merging Unit (MU). One or many • data as being extended according to the of theses Logical Devices are implemented extension rules (should be avoided but may be in a common Physical Device sometimes con- needed), fusingly called MU also. • the services provided and used, • connection in the communication system, The samples are used as current and volt- • setting of all configuration parameters as age input e.g. for protection. The trip from the defined in IEC 61850, protection device to the circuit breaker IED • defaults values of for all operational (XCBR.pos.ctl) can be transmitted over the parameters as defined in IEC 61850. same communication network using the GOOSE concept introduced in clause 3.2. The SCL is based on the eXtended Mark- up Language (XML), known also from the Another interesting example is the syn- description of Web pages, with an XML Schema chrocheck function. In case of reclosing (auto- defining the semantic use of XML in the

No. 222 - October 2005 ELECTRA 17 0508-095Mep222 7/12/05 16:51 Page 18 SC REPORT B5 description of the substation and SA configu- If these are not given, the system integrator ration. The goal of SCL is to have a formal has to make certain assumption to select the description of the SA on engineering level, i.e. proper communication architecture out of the files, which can be exchanged between pro- wide range of architectures possible with Eth- prietary tools of different suppliers. ernet used in IEC 61850.

Specification by the user The customer may specify also pre-quali- In a first approach nothing looks changed fied IEC 61850 compliant devices, e.g. differ- in a specification for IEC 61850 compliant SA ent for main 1 and main 2 protection. This will compared to previous specifications. The fol- limit the optimization process of the provider lowing elements are part of the specification: but may be of special interest to get similar SA • The single line diagram of the substation systems after a successful operation of the first • Signal lists and data flow requirements optimized system. • The specification of functionalities to be performed (including performance figures and First considerations and recommendations availability requirements if applicable) and their for the specification of IEC 61850 based SA allocation to the single line diagram systems have been published in [12]. In addi- • The interfaces both to the switchgear tion the WG 11 of the CIGRE SC B5 is working (process interface) and to the NCC (protocol) out details to be used as guideline for utili- • The geographical layout (extension, ties or other specifying parties. buildings, cable channels, etc.) • The environmental conditions Form of the specification Using SCL, many of the above-described If not more is specified the supplier will requirements can be formally specified in a Sys- translate the specification to an optimized solu- tem Specification Description file (SSD). If the tion based both on his experience and the customer does not yet do this it is left as task framework of IEC 61850. for the supplier.

Since the data model of IEC 61850 is The SSD file is used to describe the single line defined function oriented, i.e. according to the diagram and the allocated functions (feeder block functional needs but not based on certain diagram). The optional data that need to be sup- implementation in devices, a function oriented ported can also be described in the SSD file. This specification facilitates the translation to an replaces the traditional signal list, the elements IEC 61850 based SA system. All data defined of a signal list being the data of logical nodes. Up as mandatory are provided according to the to now, the signal list is not only used to describe data model in IEC 61850. If the user needs data the complete information content, but also to declared as optional this has to be specified. describe the data flow. In IEC 61850, the data If data are needed which are not specified in flow is implemented through communication ser- the standard, they have to be listed for pos- vices like report or GOOSE where the content is sible extensions. defined by data sets being a group of data.

The specification of functionality results The capabilities of an IEC 61850 compliant basically in a selection of required logical nodes. device (IED) are described in an IED Capabil- Some aspects of the functionality requirements ity Description (ICD) file. A vendor of devices may have an impact on the services, e.g. there claiming conformance to IEC 61850 has not are different command services available rang- only to supply paper documentation like a data ing from a “direct control” to “select-before- sheet but also an ICD file. operate (SBO) with enhanced security”. From specification to system design as task Availability figures or scenarios may be pro- for the system integrator vided answering the questions about the The specification has to be translated by accepted or not accepted impact of failures. the provider to a system design (see e.g.

18 ELECTRA N° 222 - Octobre 2005 0508-095Mep222 7/12/05 16:51 Page 19 REPORT SC B5 [14]). The responsibility for the system design, • The starting point of the engineering pro- including the resulting performance, is the task cess (Figure 7) is the formal description of the of the system integrator. He has more respon- single line diagram, and part of the data model sibilities in the multi-vendor environment pos- by the SSD file. sible with IEC 61850. He has to consider not • Any selected IED if IEC 61850 compli- only the direct impact of IEC 61850 but also ant has to have an IED Capability Description all boundary conditions regarding environ- (ICD) file including its potential data model. ment, performance, etc. as summarized in • A system configuration tool will take p.17. The system integrator may be part of the all these files written according to SCL and main provider or of the utility, but he has to merge these by the system engineering pro- have the know-how and experience for this job cess to a Substation Configuration Description and, very important, powerful tools compliant (SCD) file. with IEC 61850. Note that the standard is not • If the ICDs are properly selected, the data defining tools but by SCL standardized infor- of all IEDs represented by the ICD files have mation (see further) to be used by proprietary to fit with the data in the SSD file. Since the tools. data in the models represent only the source or client part, the data have to be configured Any system integration tools needs the in data sets for the transmission by the appro- SSD file and the ICD files of all devices of the priate services (e.g. Report, GOOSE) and in system. The output is the Substation Config- so-called input sections of the SCL file, since uration Description (SCD) file. For maintenance the receiver side has to be informed where the and future system modifications the SCD files data needed for the functions coming from. have to be archived as part of the project doc- • All data changes caused by the promo- umentation. tion of the IEDs from the shelf to integrated system components, i.e. in minimum some Product and system engineering with addressing information, have to be down- compatible tools loaded to the IEDs. Since the functions are not standardized, device specific tools will remain at least for the The formal SCL description will result in a next time. They are depending mostly on the consistent data exchange, allow exchanges function algorithms and their implementation between compliant tools independent from in the IEDs. If they are in series with the system the supplier and, finally, in a machine-readable configuration tool they have be IEC 61850 com- documentation of the data and communica- pliant, i.e. to be able to export and import SCL tion structure of the SA system. Any extension files if applicable. The complete engineering or update in the future will not start from the process is schematically shown in Figure 7. scratch but from the archived SCD file.

Figure 7: The engineering process using SCL files

No. 222 - October 2005 ELECTRA 19 0508-095Mep222 7/12/05 16:51 Page 20 SC REPORT B5 How to USE IEC 61850 have to be equipped with IEC 61850 interfaces. for testing and commissioning The test of the functionality has to be done same as before. Conformance testing Devices are the physical (IED) building Commissioning and Site Acceptance Test blocks of a system. To minimize problems with interoperability in a project, any IED to be inte- The site acceptance test (SAT) has to prove grated in an IEC 61850 based SA system the same as the FAT but now on site with the should be IEC 61850 compliant by itself. The switchgear in the real substation environment. report of the CIGRE TF 34.01 [8] gives some Conventional wiring requires mostly a conven- general testing guidelines for communication tional point-to-point test. In case of a process in SA, Part 10 of IEC 61850 [9] provides a frame bus, the data consistency in the SA system from specification concerning conformance testing the NCC gateway down to the switchgear has of devices including the mandatory ICD file. been already proven in the engineering pro- The goal is that testing in any test laboratory cess with the resulting SCD file. The only mis- is done in comparable and universal valid way. take could be an allocation mismatch between The conformance test is depending on the the bay units and the process bus connectors device under test but independent of a real plugged in. Only this check and outstanding project. Note that the user group UCA Inter- function tests have to be performed. This national tries to detail the test to facilitate the speeds up the SAT dramatically. procedure. The device and its content have to be the same as described by the mandatory How to use IEC 61850 ICD file. during the life cycle

System performance testing The primary equipment as a whole needs To check the performance classes as changing once every 30 – 60 years but may be defined in the mandatory part IEC 61850-5 for extended during the life cycle time of the sub- the device in a system (system conformance) station. One of the most important aspects independent from a project, the IEDs may be during the life cycle time is the facility for tested in a test system with reasonable data extensions or the refurbishment of existing traffic in the background. parts of the SA system. In this respect it is to be considered that the replacement of an IED The Factory Acceptance Test may be needed because of maintenance rea- The factory acceptance test (FAT) has to son (failure of the equipment) or because of prove that the SA system as far as assembled in needs for a performance upgrade. In most one factory fulfills the given specification of the cases the new coming in IED is not identical customer. The prerequisite is that all compo- with the previous one, additional engineering nents are conformant with IEC 61850 and that and testing works are needed. the all SCL files used in engineering, especially With IEC 61850 the whole system descrip- the resulting SCD file is available. With some tion and data remain available as formally pro- minor exceptions for systems on MV level, the vided in the SCD file. This is part of the doc- switchgear will not be available for the FAT. The umentation the user has received with the missing switchgear and other missing parts have system delivery and has to be updated for any to be simulated. For an IEC 61850 based sys- change in the system e.g. change of the event tem appropriate simulators having serial inter- list. Using this documentation and taking over faces according to the standard can easily do data coming from new devices or from new this. If the system has also an IEC 61850 process functions to be introduced in the system, the bus simulators may be plugged in to the bus system integrator can perform the required representing the switchgear. Quasi-standard- extensions much easier than in the past. ized or project specific switchgear plugs are replaced by the standardized process bus inter- A practical issue is the extension of a new face. Note that also devices monitoring the tests bay to an existing SA system, which is

20 ELECTRA N° 222 - Octobre 2005 0508-095Mep222 7/12/05 16:51 Page 21 REPORT SC B5 not yet IEC 61850 compliant. In this case it is International promotes the standard and tries recommended to build the new bay according to support all users. The intended result is seam- IEC 61850 in order to have the advantages set less communication architecture for utilities. by the standard for the life cycle of a substa- Since IEC 61850 has high impact on the tion automation system. For this reasons exten- investment and operation of power systems, sion scenarios are very important but gener- the utilities will consider the standard very ally individual per substation. actively same as the suppliers.

Note that all actual versions of the soft- References ware, hardware (IED) and switchgear are available and readable from remote if the optional [1] IEC 60870-5-101 “Telecontrol equipment feature “name plate” is used. This nameplate and systems - Part 5-101: Transmission protocols - is provided in Logical Nodes, Logical Devices, Companion standard for basic telecontrol tasks” Physical Devices and as external nameplate for [2] IEC 60870-5-104 “Telecontrol equipment and systems - Part 5-104: Transmission protocols - switchgear also. Network access for IEC 60870-5-101 using standard transport profiles” Outlook and conclusions [3] IEC 60870-5-103 “Telecontrol equipment and systems – Part 5-103: Transmission protocols – Companion standard for the informative interface The Standard IEC 61850 covers all aspects of protection equipment related to the communication inside substa- [4] IEC 61850 “Communication networks and tion. It supports important issues as the nam- systems in substations” (www.iec.ch) ing and the engineering capabilities but also [5] IEC 61850-7-2 “Communication networks and conformity, testing, etc. It is a comprehensive systems in substations – Part 7-2: Basic communica- approach for the conception of the substation tion structure for substation and feeder equipment – Abstract communication service interface (ACSI) automation and protection with serial com- [6] IEC 61850-7-4 “Communication networks munication. It doesn’t mean that all delivered and systems in substations – Part 7-4: Basic com- systems will have the same “quality” inde- munication structure for substation and feeder pendently of the manufacturer because archi- equipment – Compatible logical node classes and data classes” tecture remains free (architecture of the com- [7] IEC 61850-7-3 “Communication networks munication system as well as location of the and systems in substations – Part 7-3: Basic com- different functionality) as well as the quality of munication structure for substation and feeder each function involved (e.g. protection func- equipment – Common data classes” tions). The first experiences done by manu- [8] IEC 61850-5 “Communication networks and systems in substations – Part 5: Communication facturers and utilities have now to confirm if requirements for functions and device models the expectations are fulfilled and if some exten- [9] K.P. Brand et al., Conformance Testing sions inside the standard will be needed. Guidelines for Communication in Substations, Cigré Report 34-01 – Ref. No. 180, August 2002 Besides the mentioned maintenance of the [10] IEC 61850-10 “Communication networks and standard for communication within substations, systems in substations - Part 10: Conformance testing” activities have been started or are envisaged to [11] K.P.Brand, V.Lohmann, W.Wimmer “Sub- station Automation Handbook”, UAC 2003, ISBN 3- use IEC 61850 also outside the substation. Within 85759-951-5, 2003 (www.uac.ch) IEC, there exists already working groups using the [12] K.P.Brand, M.Janssen “ The specification of standard in wind power, hydro-power and dis- IEC 61850 based Substation Automation Systems” tributed energy resources (DER). The feasibility Paper presented at the DistribuTECH 2005, January 25-27, San Diego of IEC 61850 for the link to the NCC has been [13] CIGRE SC B5, WG11 “The introduction of proven, a harmonization between the data model IEC 61850 and its impact on protection and automa- of IEC 61850 and the CIM model on Network tion within substations”, work started in 2003, report Level is in progress. New work items to use IEC to be scheduled for 2005/2006 61850 for communication between both ends of [14] K.P. Brand, C. Brunner, W. Wimmer “Design a line protection (protection application) are in of IEC 61850 based Substation Automation Systems according to customer requirements”, Paper B5-103 preparation. The IEC TC57 WG10 takes care to of the B5 Session at CIGRE Plenary Meeting, Paris, the common data model, the user group UCA 2004, 8 pages ■

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