The International Electrotechnical Commission was created in 1906 at an international conference attended by 13 countries most interested in such an organization. The date of the beginning of international cooperation in electrical engineering is considered to be 1881, when the first International Congress on Electricity took place. Later, in 1904, government delegates to the Congress decided that a special organization was needed to standardize the parameters of electrical machines and terminology in this area.

After World War II, when ISO was created, the IEC became an autonomous organization within it. But organizational, financial issues and standardization objects were clearly separated. IEC deals with standardization in the field of electrical engineering, electronics, radio communications, and instrument making. These areas are outside the scope of ISO.

Most IEC member countries are represented in it by their national standardization organizations (Russia is represented by Gosstandart of the Russian Federation); in some countries, special committees for participation in the IEC have been created that are not part of the structure of national standardization organizations (France, Germany, Italy, Belgium, etc. ).

The representation of each country in the IEC takes the form of a national committee. IEC members are more than 40 national committees, representing 80% of the world's population, which consumes more than 95% of the world's electricity. The official languages ​​of the IEC are English, French and Russian.

The main purpose of the organization, which is defined by its Charter- promoting international cooperation on standardization and related issues in the field of electrical and radio engineering through the development of international standards and other documents.

National committees of all countries form the Council - the highest governing body of the IEC. Annual meetings of the Council, which are held alternately in different IEC member countries, are devoted to solving the entire range of issues related to the organization’s activities. Decisions are made by a simple majority of votes, and the president has the casting vote, which he exercises in the event of an equal distribution of votes.

The main coordinating body of the IEC is the Action Committee. In addition to its main task - coordinating the work of technical committees - the Action Committee identifies the need for new areas of work, develops methodological documents that support technical work, participates in resolving issues of cooperation with other organizations, and carries out all tasks of the Council.

Subordinate to the Action Committee are advisory groups, which the Committee has the right to create if there is a need for coordination on specific problems in the activities of the TC. Thus, two advisory groups divided the development of safety standards among themselves: the Advisory Committee on. Electrical safety issues (AKOS) coordinates the actions of about 20 technical committees and PCs on electrical household appliances, radio-electronic equipment, high-voltage equipment, etc., and the Advisory Committee on Electronics and Communications (ASET) deals with other standardization objects. In addition, the Action Committee considered it appropriate to more effectively coordinate the work on creating international standards to organize the Coordination Group on Electromagnetic Compatibility (CGEMC), the Coordination Group on Information Technology (CGIT) and the Working Group on Size Coordination (Fig. 11.2).

The structure of the IEC technical bodies that directly develop international standards is similar to ISO: these are technical committees (TC), subcommittees (SC) and working groups (WG). 15-25 countries participate in the work of each TC. The largest number of TC and PC secretariats are held by France, USA, Germany, Great Britain, Italy, and the Netherlands. Russia maintains six secretariats.

International IEC standards can be divided into two types: general technical, intersectoral in nature, and standards containing technical requirements for specific products. The first type includes regulatory documents on terminology, standard voltages and frequencies, various types of tests, etc. The second type of standards covers a huge range from household electrical appliances to communication satellites. Every year, the IEC program includes more than 500 new topics on international standardization.

Main objects of IEC standardization:

Materials for the electrical industry (liquid, solid, gaseous dielectrics, copper, aluminum, their alloys, magnetic materials);

Electrical equipment for industrial purposes (welding machines, engines, lighting equipment, relays, low-voltage devices, cables, etc.);

Electrical power equipment (steam and hydraulic turbines, power lines, generators, transformers);

Electronics industry products (integrated circuits, microprocessors, printed circuit boards, etc.);

Electronic equipment for household and industrial purposes;

Power tools;

Equipment for communication satellites;

Terminology.

The IEC has adopted more than 2 thousand international standards. In content, they differ from ISO standards in that they are more specific: they set out technical requirements for products and their testing methods, as well as safety requirements, which is relevant not only for IEC standardization objects, but also for the most important aspect of confirmation of conformity - certification for compliance with the requirements of standards on safety. To ensure this area, which is of current importance in international trade, the IEC develops special international standards for the safety of specific products. In view of the above, as practice shows, IEC international standards are more suitable for direct application in member countries than ISO standards.

Attaching great importance to the development of international safety standards, ISO and IEC have adopted ISO/IEC Guide 51, General requirements for the presentation of safety issues in the preparation of standards. It notes that safety is an object of standardization that manifests itself in the development of standards in many different forms, at different levels, in all areas of technology and for the vast majority of products. The essence of the concept of “safety” is interpreted as ensuring a balance between preventing the danger of causing physical harm and other requirements that the product must satisfy. It should be borne in mind that absolute safety practically does not exist, therefore, even at the highest level of safety, products can only be relatively safe.

When manufacturing products, safety-related decisions are usually based on risk calculations and safety assessments. Risk assessment (or establishing the likelihood of harm) is based on accumulated empirical data and scientific research. Assessing the degree of safety is associated with a probable level of risk, and safety standards are almost always established at the state level (in the EU - through Directives and technical regulations; in the Russian Federation - so far by mandatory requirements of state standards). Typically, safety standards themselves are influenced by the level of socio-economic development and education of society. Risks depend on the quality of the design and production process, as well as, no less, on the conditions of use (consumption) of the product.

Based on this concept of safety, ISO and IEC believe that safety will be facilitated by the application of international standards that establish safety requirements. This may be a standard that relates solely to safety or may contain safety requirements along with other technical requirements. When preparing safety standards, they identify both the characteristics of the object of standardization that may have a negative impact on humans and the environment, as well as methods for establishing safety for each product characteristic. But The main purpose of standardization in the field of safety is to find protection against various types of hazards. The scope of activities of the IEC includes: injury hazard, electric shock hazard, technical hazard, fire hazard, explosion hazard, chemical hazard, biological hazard, equipment radiation hazard (sound, infrared, radio frequency, ultraviolet, ionizing, radiation, etc.).

The procedure for developing an IEC standard is similar to that used by ISO. On average, they work on a standard for 3-4 years, and often it lags behind the pace of product renewal and the appearance of new products on the market. In order to reduce deadlines, the IEC practices the publication of a Technical Guidance Document (TOD) adopted through a short procedure, containing only the idea of ​​a future standard. It is valid for no more than three years and is canceled after the publication of the standard created on its basis.

An accelerated development procedure is also applied, relating, in particular, to shortening the voting cycle, and, what is more effective, to expanding the conversion of regulatory documents adopted by other international organizations or national standards of member countries into international IEC standards. Technical means also help speed up the work on creating a standard: an automated system for monitoring the progress of work, the Teletext information system, organized on the basis of the Central Bureau. More than 10 national committees have become users of this system.

Within the IEC, the International Special Committee on Radio Interference (CISPR) has a somewhat special status, which standardizes methods for measuring radio interference emitted by electronic and electrical devices. Permissible levels of such interference are the subject of direct technical legislation in almost all developed countries. Certification of such devices is carried out for compliance with CISPR standards.

Not only national committees participate in CISPR, but also international organizations: European Broadcasting Union, International Radio and Television Organization, International Union of Electrical Energy Manufacturers and Distributors, International Conference on Large Electrical Systems, International Union of Railways, International Union of Public Transport, International Union on electrothermy. The International Radiocommunication Committee and the International Civil Aviation Organization participate as observers in the work of the committee. CISPR develops both regulatory and informational international documents:

international standards of technical requirements, which regulate methods for measuring radio interference and contain recommendations for the use of measuring equipment;

reports, which present the results of scientific research on CISPR issues.

International standards have the greatest practical application, which establish technical requirements and maximum levels of radio interference for various sources: vehicles, pleasure boats, internal combustion engines, fluorescent lamps, televisions, etc.

Event protocol - in your own words

If we consider the classroom allegory, which works well, cyclic protocols like Modbus, Profibus, Fieldbus are like polling each of the students sequentially. Even if there is no interest in the device (student). Event protocols work differently. A request is made not to each network device (student) sequentially, but to the class as a whole, then information is collected from the device with a changed state (student who raised his hand). Thus, there is a significant saving in network traffic. Network devices do not accumulate errors when the connection is poor. Given that event delivery occurs with a time stamp, even if there is some delay, the bus master receives information about events that have occurred on remote objects.

Event protocols are mainly used at power generation facilities, as well as remote control systems for various gateway and watershed systems. They are used wherever remote dispatching and control of objects very distant from each other is necessary.

History of the development and implementation of event protocols in the automation of power facilities

An example of one of the first successful attempts to standardize information exchange for industrial controllers is the ModBus protocol, developed by Modicon in 1979. Currently, the protocol exists in three versions: ModBus ASCII, ModBus RTU and ModBus TCP; its development is carried out by the non-profit organization ModBus-IDA. Despite the fact that ModBus belongs to the application layer protocols of the OSI network model and regulates the functions of reading and writing registers, the correspondence of registers to measurement types and measurement channels is not regulated. In practice, this leads to incompatibility of protocols of devices of different types, even from the same manufacturer, and the need to support a large number of protocols and their modifications by the built-in USPD software (with a two-level polling model - collection server software) with limited ability to reuse program code. Considering the selective adherence to standards by manufacturers (the use of unregulated algorithms for calculating the checksum, changing the byte order, etc.), the situation is aggravated even more. Today, the fact that ModBus is not able to solve the problem of protocol separation of measuring and control equipment for power systems is obvious. The DLMS/COSEM (Device Language Message Specification) specification, developed by the DLMS User Association and developed into the IEC 62056 family of standards, is designed to provide, as stated on the official website of the association, “an interoperable environment for structural modeling and data exchange with the controller” . The specification separates the logical model and the physical representation of specialized equipment, and also defines the most important concepts (register, profile, schedule, etc.) and operations on them. The main standard is IEC 62056-21, which replaced the second edition of IEC 61107.
Despite a more detailed study of the device representation model and its operation compared to ModBus, the problem of completeness and “purity” of the implementation of the standard, unfortunately, remains. In practice, polling a device with declared support for DLMS from one manufacturer with a polling program from another manufacturer is either limited to the basic parameters, or simply impossible.It should be noted that the DLMS specification, unlike the ModBus protocol, turned out to be extremely unpopular among domestic manufacturers of metering devices, primarily due to the greater complexity of the protocol, as well as additional overhead costs for establishing a connection and obtaining the device configuration.
The full support of existing standards by manufacturers of measuring and control equipment is not sufficient to overcome intra-system information disunity. Support for a particular standardized protocol declared by the manufacturer, as a rule, does not mean its full support and the absence of introduced changes. An example of a set of foreign standards is the family of IEC 60870-5 standards created by the International Electrotechnical Commission.
Various implementations of IEC 60870-5-102 - a general standard for the transfer of integral parameters in power systems - are presented in devices from a number of foreign manufacturers: Iskraemeco d.d. (Slovenia), Landis&Gyr AG (Switzerland), Circutor SA (Spain), EDMI Ltd (Singapore), etc., but in most cases - only as additional ones. Proprietary protocols or variations of DLMS are used as the main data transfer protocols. It is worth noting that IEC 870-5-102 is not widely used for another reason: some manufacturers of metering devices, including domestic ones, have implemented modified telemechanical protocols in their devices (IEC 60870-5-101, IEC 60870-5 -104), ignoring this standard.

A similar situation is observed among relay protection and automation manufacturers: in the presence of the current IEC 60870-5-103 standard, a ModBus-like protocol is often implemented. The prerequisite for this, obviously, was the lack of support for these protocols by most upper-level systems. Telemechanical protocols described in the IEC 60870-5-101 and IEC 60870-5-104 standards can be used if it is necessary to integrate telemechanics and electricity metering systems. In this regard, they have found wide application in dispatch systems.

Automation Protocol Technical Specifications

In modern automation systems, as a result of constant modernization of production, the tasks of building distributed industrial networks using event-based data transfer protocols are increasingly encountered. To organize industrial networks of power facilities, many interfaces and data transfer protocols are used, for example, IEC 60870-5-104, IEC 61850 (MMS, GOOSE, SV), etc. They are necessary for data transfer between sensors, controllers and actuators (AM), connections between the lower and upper levels of the automated process control system.

Protocols are developed taking into account the specifics of the technological process, ensuring a reliable connection and high accuracy of data transfer between various devices. Along with reliable operation in harsh conditions, functionality, flexibility in design, ease of integration and maintenance, and compliance with industrial standards are becoming increasingly important requirements in automated process control systems. Let's look at the technical features of some of the above protocols.

IEC 60870-5-104 protocol

IEC 60870-5-104 formalizes the encapsulation of the ASDU from IEC 60870-5-101 into standard TCP/IP networks. Both Ethernet and modem connections using the PPP protocol are supported. Cryptographic data security is formalized in the IEC 62351 standard. The standard port is TCP 2404.
This standard specifies the use of an open TCP/IP interface for a network containing, for example, a LAN (local area network) for a telecontrol device that transmits ASDU in accordance with IEC 60870-5-101. Routers, including routers for WAN (wide area network) of various types (for example, X.25, Frame Relay, ISDN, etc.), can be connected through a common TCP/IP-LAN interface.

Example of a general application architecture of IEC 60870-5-104

The transport layer interface (the interface between the user and TCP) is a flow-oriented interface that does not define any start-stop mechanisms for the ASDU (IEC 60870-5-101). To define the start and end of an ASDU, each APCI header includes the following markings: a start character, an indication of the length of the ASDU, along with a control field. Either the complete APDU or (for control purposes) only the APCI fields may be transmitted.

IEC 60870-5-104 protocol data packet structure

Wherein:

APCI - Application Level Control Information;
- ASDU - Data Unit. Maintained by the Application Layer (Application Layer Data Block);
- APDU - Application Layer Protocol Data Unit.
- START 68 N defines the starting point within the data stream.
The APDU length specifies the length of the APDU body, which consists of the four bytes of the APCI control field plus the ASDU. The first byte counted is the first byte of the control field, and the last byte counted is the last byte of the ASDU. The maximum ASDU length is limited to 249 bytes because The maximum APDU field length is 253 bytes (APDUmax=255 minus 1 start byte and 1 length byte), and the control field length is 4 bytes.
This data transfer protocol is currently the de facto standard dispatch protocol for enterprises in the electric power sector. The data model in this standard is more developed, but it does not provide any unified description of the power facility.

DNP-3 protocol

DNP3 (Distributed Network Protocol) is a data transfer protocol used for communication between ICS components. It was designed for convenient interaction between different types of devices and control systems. Can be used at various levels of automated process control systems. There is a Secure Authentication extension for DNP3 for secure authentication.
In Russia, this standard is poorly distributed, but some automation devices still support it. For a long time, the protocol was not standardized, but now it has been approved as the IEEE-1815 standard. DNP3 supports both RS-232/485 serial communications and TCP/IP networks. The protocol describes three layers of the OSI model: application, data link and physical. Its distinctive feature is the ability to transfer data both from a master device to a slave device, and between slave devices. DNP3 also supports sporadic data transfer from slave devices. Data transmission is based, as in the case of IEC-101/104, on the principle of transmitting a table of values. In this case, in order to optimize the use of communication resources, not the entire database is sent, but only its variable part.
An important difference between the DNP3 protocol and those discussed earlier is the attempt to describe the data model objectively and the independence of data objects from the transmitted messages. To describe the data structure in DNP3, an XML description of the information model is used. DNP3 is based on three layers of the OSI network model: application (operates with objects of basic data types), channel (provides several ways to retrieve data) and physical (in most cases, RS-232 and RS-485 interfaces are used). Each device has its own unique address for a given network, represented as an integer from 1 to 65520. Basic terms:
- Outslation - slave device.
- Master - master device.
- Frame (frame) - packets transmitted and received at the data link layer. The maximum packet size is 292 bytes.
- Static data - data associated with some real value (for example, a discrete or analog signal)
- Event data - data associated with any significant event (for example, state changes, reaching a threshold by a value). There is an option to attach a timestamp.
- Variation (variation) - determines how the value is interpreted, characterized by an integer.
- Group (group) - determines the type of value, characterized by an integer (for example, a constant analog value belongs to group 30, and an event analog value to group 32). For each group, a set of variations is assigned, with the help of which the meanings of this group are interpreted.
- Object (object) - frame data associated with a specific value. The object format depends on the group and variation.
A list of variations is given below.

Variations for constant data:

Variations for event data:

Flags imply the presence of a special byte with the following information bits: the data source is on-line, the data source was rebooted, the connection to the source was lost, the value was forced to be written, the value is outside the permissible limits.

Frame header:

Synchronization - 2 bytes of synchronization allowing the recipient to identify the beginning of the frame. Length - the number of bytes in the remainder of the packet, excluding CRC octets. Connection control - a byte for coordinating the reception of a frame transmission. Destination address - the address of the device to which the transfer is assigned. Source address - the address of the device performing the transmission. CRC - checksum for the header byte. The data section of the DNP3 frame contains (in addition to the data itself) 2 bytes of CRC for every 16 bytes of transmitted information. The maximum number of data bytes (not including CRC) for one frame is 250.

IEC 61850 MMS protocol

MMS (Manufacturing Message Specification) is a data transfer protocol using client-server technology. The IEC 61350 standard does not describe the MMS protocol. Chapter IEC 61850-8-1 only describes how to assign data services described by the IEC 61850 standard to the MMS protocol described by the ISO/IEC 9506 standard. In order to better understand what this means, it is necessary to take a closer look at how the IEC standard 61850 describes abstract communication services and what they do.
One of the main ideas embedded in the IEC 61850 standard is that it does not change over time. In order to ensure this, the chapters of the standard successively describe first the conceptual issues of data transfer within and between power facilities, then the so-called “abstract communication interface” is described, and only at the final stage the purpose of abstract models for data transfer protocols is described.

Thus, conceptual issues and abstract models are independent of the data transmission technologies used (wired, optical or radio channels), and therefore will not require revision caused by progress in the field of data transmission technologies.
Abstract communication interface described by IEC 61850-7-2. includes both a description of device models (that is, it standardizes the concepts of “logical device”, “logical node”, “control block”, etc.). and a description of data transfer services. One such service is SendGOOSEMessage. In addition to the specified service, more than 60 services are described that standardize the procedure for establishing communication between the client and the server (Associate, Abort, Release), reading the information model (GetServerDirectory, GelLogicalDeviceDirectory, GetLogicalNodeDirectory), reading variable values ​​(GetAllDataValues, GetDataValues, etc.) , transfer of variable values ​​in the form of reports (Report) and others. Data transfer in the listed services is carried out using client-server technology.

For example, in this case the server can be a relay protection device, and the client can be a SCADA system. Services for reading the information model allow the client to read the complete information model from the device, that is, to recreate a tree of logical devices, logical nodes, elements and data attributes. In this case, the client will receive a complete semantic description of the data and its structure. Services for reading variable values ​​allow you to read the actual values ​​of data attributes, for example, by periodic polling. The reporting service allows you to configure the sending of certain data when certain conditions are met. One variant of such a condition could be a change of one kind or another associated with one or more elements from the data set. To implement the described abstract data transmission models, the IEC 61850 standard describes the assignment of abstract models to a specific protocol. For the services under consideration, this protocol is MMS, described by the ISO/IEC 9506 standard.

MMS defines:
- a set of standard objects on which operations are performed that must exist in the device (for example: reading and writing variables, signaling events, etc.),
- a set of standard messages. which are exchanged between the client and the north to carry out management operations;
- a set of rules for encoding these messages (that is, how values ​​and parameters are assigned to bits and bytes during transmission);
- a set of protocols (rules for exchanging messages between devices). Thus, MMS does not define application services, which, as we have already seen, are defined by the IEC 61850 standard. Moreover, the MMS protocol itself is not a communication protocol, it only defines messages that must be transmitted over a specific network. MMS uses the TCP/IP stack as the communication protocol.

The general structure of using the MMS protocol for implementing data transfer services in accordance with IEC 61850 is presented below.


Diagram of data transfer via MMS protocol

Such a rather complex, at first glance, system ultimately makes it possible, on the one hand, to ensure the immutability of abstract models (and, consequently, the immutability of the standard and its requirements), on the other hand, to use modern communication technologies based on the IP protocol. However, it should be noted that due to the large number of assignments, the MMS protocol is relatively slow (for example, compared to GOOSE), so its use for real-time applications is impractical. The main purpose of the MMS protocol is to implement the functions of an automated process control system, that is, the collection of telesignaling and telemetering data and the transmission of telecontrol commands.
For the purpose of collecting information, the MMS protocol provides two main capabilities:
- data collection using periodic polling of the server(s) by the client;
- transfer of data to the client by the server in the form of reports (sporadic).
Both of these methods are in demand when setting up and operating an automated process control system; to determine the areas of their application, we will take a closer look at the operating mechanisms of each.
At the first stage, a connection is established between the client and server devices (the “Association” service). The connection is initiated by the client by contacting the server using its IP address.

Client-server data transfer mechanism

The next step is that the client requests certain data from the server and receives a response from the server with the requested data. For example, after establishing a connection, a client can request the server for its information model using the services GetServerDirectory, GetLogicalDeviceDirectory, GetLogicalNodeDiretory. Requests will be made sequentially:
- after a GetServerDirectory request, the server will return a list of available logical devices.
- after a separate GelLogicalDeviceDirectory request for each logical device, the server will return a list of logical nodes in each of the logical devices.
- The GetLogicalNodeDirectory request for each individual logical node returns its objects and data attributes.
As a result, the client calculates and recreates the complete information model of the server device. In this case, the actual values ​​of the attributes will not yet be read, that is, the read “tree” will contain only the names of logical devices, logical nodes, data objects and attributes, but without their values. The third step can be to read the actual values ​​of all data attributes. In this case, either all attributes can be read using the GetAllDataValues ​​service, or only individual attributes using the GetDataValues ​​service. Upon completion of the third stage, the client will completely recreate the server information model with all the values ​​of the data attributes. It should be noted that this procedure involves the exchange of fairly large volumes of information with a large number of requests and responses, depending on the number of logical devices of logical nodes and the number of data objects implemented by the server. This also leads to a fairly high load on the hardware of the device. These steps can be carried out at the stage of setting up the SCADA system so that the client, having read the information model, can access the data on the server. However, during further operation of the system, regular reading of the information model is not required. It is also inappropriate to constantly read attribute values ​​using regular polling. Instead, the reporting service - Report - can be used. IEC 61850 defines two types of reports - buffered and unbuffered. The main difference between a buffered report and a non-buffered one is that when using the former, the generated information will be delivered to the client even if at the time the server is ready to issue the report there is no connection between it and the client (for example, the corresponding communication channel has been broken). All generated information is accumulated in the device’s memory and will be transferred as soon as the connection between the two devices is restored. The only limitation is the amount of server memory allocated for storing reports. If during that period of time when there was no connection, quite a lot of events occurred that caused the generation of a large number of reports, the total volume of which exceeded the permissible amount of server memory, then some information may still be lost and new generated reports will “displace” previously generated data from the buffer , however, in this case, the server, through a special attribute of the control block, will signal to the client that a buffer overflow has occurred and data loss is possible. If there is a connection between the client and the server - both when using a buffered and when using a non-buffered report - the transfer of data to the client can be immediate upon the occurrence of certain events in the system (provided that the time interval for which events are recorded , is equal to zero). When it comes to reports, we do not mean monitoring all objects and data attributes of the server information model, but only those that interest us, combined into so-called “data sets”. Using a buffered/unbuffered report, you can configure the server not only to transmit the entire monitored set of data, but also to transmit only those data objects/attributes with which certain types of events occur within a user-defined time interval.
To do this, in the structure of the control block for the transmission of buffered and non-buffered reports, it is possible to specify categories of events, the occurrence of which must be monitored and, upon the fact of which, only those data objects/attributes affected by these events will be included in the report. The following categories of events are distinguished:
- data change (dchg). When you set this option, the report will include only those data attributes whose values ​​have changed, or only those data objects whose attribute values ​​have changed.
- change of quality attribute (qchg). By setting this option, the report will include only those quality attributes whose values ​​have changed, or only those data objects whose quality attributes have changed.
- data update (dupd). When you set this parameter, the report will include only those data attributes whose values ​​have been updated, or only those data objects whose attribute values ​​have been updated. By updating we mean, for example, the periodic calculation of one or another harmonic component and recording its new value in the corresponding data attribute. However, even if the value based on the calculation results for the new period has not changed, the data object or the corresponding data attribute is included in the report.
You can also configure the report to report the entire monitored set of data. Such a transfer can be performed either at the server’s initiative (integrity condition) or at the client’s initiative (general-interrogation). If data generation is entered according to the integrity condition, then the user also needs to indicate the period for data generation by the server. If data generation is entered according to the general-interrogation condition. the server will generate a report with all elements of the data set upon receipt of the corresponding command from the client.
The report transmission mechanism has important advantages over the periodic polling method: the load on the information network is significantly reduced, the load on the processor of the server device and client device is reduced, and fast delivery of messages about events occurring in the system is ensured. However, it is important to note that all the advantages of using buffered and non-buffered reports can be achieved only if they are configured correctly, which, in turn, requires sufficiently high qualifications and extensive experience from the personnel performing equipment setup.
In addition to the services described, the MMS protocol also supports equipment control models - the formation and transmission of event logs, as well as file transfer, which allows you to transfer, for example, files of emergency oscillograms. These services require separate consideration. The MMS protocol is one of the protocols to which the abstract services described by the IEC 61850-7-2 standard can be assigned. At the same time, the emergence of new protocols will not affect the models described by the standard, thereby ensuring that the standard remains unchanged over time. To assign models and services to the MMS protocol, the IEC 61850-8-1 chapter is used. The MMS protocol provides various mechanisms for reading data from devices, including reading data on demand and transmitting data in the form of reports from the server to the client. Depending on the task being solved, the correct data transmission mechanism must be selected and its appropriate settings must be made, which will allow the entire set of communication protocols of the IEC 61850 standard to be effectively used at the power facility.

IEC 61850 GOOSE protocol

The GOOSE protocol, described in Chapter IEC 61850-8-1, is one of the most widely known protocols provided by the IEC 61850 standard. The abbreviation GOOSE - Generic Object-Oriented Substation Event - can be translated literally as “general object-oriented event in a substation”. However, in practice, you should not attach much importance to the original name, since it does not give any idea about the protocol itself. It is much more convenient to understand the GOOSE protocol as a service designed to exchange signals between relay protection devices in digital form.

Generating GOOSE messages

The data model of the IEC 61850 standard specifies that data should be formed into sets - Dataset. Data sets are used to group data that will be sent by a device using the GOOSE message mechanism. Subsequently, the GOOSE sending control block specifies a link to the created data set, in which case the device knows what data to send. It should be noted that within one GOOSE message, both one value (for example, an overcurrent protection start signal) and several values ​​simultaneously (for example, a start signal and an overcurrent protection signal, etc.) can be sent. The receiving device, at the same time, can extract from the packet only the data that it needs. The transmitted GOOSE message packet contains all the current values ​​of the data attributes included in the data set. When any of the attribute values ​​change, the device immediately initiates sending a new GOOSE message with updated data.

GOOSE transmissionmessages

According to its purpose, the GOOSE message is intended to replace the transmission of discrete signals over the operational current network. Let's consider what requirements are imposed on the data transfer protocol. To develop an alternative to signal transmission circuits between relay protection devices, the properties of information transmitted between relay protection devices via discrete signals were analyzed:
- small amount of information - the values ​​“true” and “false” (or logical “zero” and “one”) are actually transmitted between the terminals;
- high speed of information transfer is required - most of the discrete signals transmitted between relay protection and automation devices directly or indirectly affect the speed of elimination of the abnormal mode, therefore signal transmission must be carried out with a minimum delay;
- a high probability of message delivery is required - to implement critical functions, such as issuing a command to turn off a circuit breaker from a relay protection and automation system, exchanging signals between relay protection and automation equipment when performing distributed functions, it is necessary to ensure guaranteed delivery of a message both in the normal mode of operation of the digital data transmission network and in the event of it short-term failures;
- the ability to transmit messages to several recipients at once - when implementing some distributed functions of relay protection and automation, data transfer from one device to several at once is required;
- it is necessary to monitor the integrity of the data transmission channel - the presence of a diagnostic function for the state of the data transmission channel allows you to increase the availability factor during signal transmission, thereby increasing the reliability of the function performed with the transmission of the specified message.

The requirements presented led to the development of a GOOSE message mechanism that meets all the requirements. In analog signal transmission circuits, the main delay in signal transmission is caused by the response time of the device’s discrete output and the bounce filtering time at the discrete input of the receiving device. The signal propagation time along the conductor is short in comparison.
Similarly, in digital data networks, the main delay is caused not so much by the transmission of the signal over the physical medium, but by its processing inside the device. In the theory of data transmission networks, it is customary to segment data transmission services in accordance with the levels of the OSI model, as a rule, going down from the “Application”, that is, the level of applied data presentation, to the “Physical”, that is, the level of physical interaction of devices. In the classic view, the OSI model has only seven layers: physical, data link, network, transport, session, presentation and application. However, the implemented protocols may not have all of the specified layers, that is, some layers may be skipped.
The mechanism of operation of the OSI model can be clearly illustrated using the example of data transfer when viewing WEB pages on the Internet on a personal computer. The content of pages is transferred to the Internet using the HTTP (Hypertext Transfer Protocol), which is an application-level protocol. HTTP data transfer is usually carried out by the TCP (Transmission Control Protocol) transport protocol. TCP protocol segments are encapsulated in network protocol packets, which in this case is IP (Internet Protocol). TCP packets comprise Ethernet link layer protocol frames, which can be transmitted using different physical layers depending on the network interface. Thus, the data of the page being viewed on the Internet goes through at least four levels of transformation when forming a sequence of bits at the physical level, and then the same number of steps of reverse transformation. This number of conversions leads to delays both during the formation of a sequence of bits for the purpose of their transmission, and during the reverse conversion in order to obtain the transmitted data. Accordingly, to reduce delay times, the number of transformations should be kept to a minimum. That is why data via the GOOSE protocol (application layer) is assigned directly to the data link layer - Ethernet, bypassing other layers.
In general, Chapter IEC 61850-8-1 provides two communication profiles that describe all data transfer protocols provided for by the standard:
- “MMS” profile;
- “Non-MMS” profile (that is, non-MMS).
Accordingly, data transfer services can be implemented using one of the specified profiles. The GOOSE protocol (as well as the Sampled Values ​​protocol) refers specifically to the second profile. Using a “shortened” stack with a minimum number of transformations is an important, but not the only, way to speed up data transfer. The use of data prioritization mechanisms also helps speed up data transfer via the GOOSE protocol. Thus, for the GOOSE protocol, a separate Ethernet frame identifier is used - Ethertype, which obviously has a higher priority compared to other traffic, for example, transmitted using the IP network layer. In addition to the mechanisms discussed above, the Ethernet GOOSE message frame can also be provided with IEEE 802.1Q priority labels. as well as virtual local network labels of the ISO/IEC 8802-3 protocol. Such labels allow you to increase the priority of frames when processing them by network switches. These mechanisms for increasing priority will be discussed in more detail in subsequent publications.

The use of all the considered methods allows us to significantly increase the priority of data transmitted via the GOOSE protocol compared to other data transmitted over the same network using other protocols, thereby minimizing delays both when processing data inside devices of data sources and receivers, as well as and when processed by network switches.

Sending information to multiple recipients

To address frames at the link level, the physical addresses of network devices - MAC addresses - are used. At the same time, Ethernet allows for so-called group messaging (Multicast). In this case, the multicast address is indicated in the recipient MAC address field. For multicast broadcasts using the GOOSE protocol, a certain range of addresses is used.

Range of multicast addresses for GOOSE messages

Messages with the value “01” in the first octet of the address are sent to all physical interfaces on the network, so in fact multicast does not have fixed recipients, and its MAC address is rather an identifier of the broadcast itself, and does not directly point to its recipients.

Thus, the MAC address of a GOOSE message can be used, for example, when organizing message filtering on a network switch (MAC filtering), and the specified address can also serve as an identifier to which receiving devices can be configured.
Thus, the transmission of GOOSE messages can be compared to a radio broadcast: the message is broadcast to all devices on the network, but in order to receive and subsequently process the message, the receiving device must be configured to receive this message.


GOOSE message transmission scheme

The transmission of messages to several recipients in Multicast mode, as well as the requirements for high data transfer rates, do not allow receiving delivery confirmations from recipients when transmitting GOOSE messages. The procedure of sending data, generating an acknowledgment by the receiving device, receiving and processing it by the sending device, and then resending it if the attempt fails would take too much time, which could lead to excessive delays in the transmission of critical signals. Instead, a special mechanism was implemented for GOOSE messages to ensure a high probability of data delivery.

Firstly, in the absence of changes in the transmitted data attributes, packets with GOOSE messages are transmitted cyclically at a user-specified interval. The cyclic transmission of GOOSE messages allows you to constantly diagnose the information network. A device configured to receive a message waits for it to arrive at specified intervals. If the message does not arrive within the waiting time, the receiving device can generate a signal about a malfunction in the information network, thus notifying the dispatcher about the problems that have arisen.
Secondly, when one of the attributes of the transmitted data set changes, no matter how much time has passed since the previous message was sent, a new packet is generated that contains the updated data. After which the sending of this packet is repeated several times with a minimum time delay, then the interval between messages (if there are no changes in the transmitted data) again increases to the maximum.


Interval between sending GOOSE messages

Thirdly, the GOOSE message packet contains several counter fields, which can also be used to monitor the integrity of the communication channel. Such counters, for example, include the cyclic send counter (sqNum), the value of which varies from 0 to 4,294,967,295 or until the transmitted data changes. With each change in the data transmitted in the GOOSE message, the sqNum counter will be reset, and another counter, stNum, will also be increased by 1, also cyclically changing in the range from 0 to 4,294,967,295. Thus, if several packets are lost during transmission, this loss can be tracked using two specified counters.

Finally, fourthly, it is also important to note that the GOOSE message, in addition to the value of the discrete signal itself, may also contain a sign of its quality, which identifies a specific hardware failure of the information source device, whether the information source device is in testing mode, and a number of other abnormal conditions. modes. Thus, the receiving device, before processing the received data according to the provided algorithms, can check this quality attribute. The above can prevent incorrect operation of information receiving devices (for example, their false operation).
It should be borne in mind that some of the built-in mechanisms for ensuring the reliability of data transmission, if used incorrectly, can lead to a negative effect. Thus, if the maximum interval between messages is chosen too short, the load on the network increases, although, from the point of view of the availability of the communication channel, the effect of reducing the transmission interval will be extremely insignificant.
When data attributes change, transmitting packets with a minimum delay causes increased load on the network (“information storm” mode), which theoretically can lead to delays in data transmission. This mode is the most complex and should be taken as calculated when designing an information network. However, it should be understood that the peak load is very short-lived and its multiple decrease, according to our experiments in the laboratory to study the functional compatibility of devices operating under the terms of the IEC 61850 standard, is observed at an interval of 10 ms.

When building relay protection systems based on the GOOSE protocol, the procedures for their adjustment and testing change. Now the setup stage consists of organizing the Ethernet network of the power facility. which will include all relay protection devices. between which data exchange is required. To verify that the system is configured and enabled in accordance with the project requirements, it becomes possible to use a personal computer with special pre-installed software (Wireshak, GOOSE Monitor, etc.) or special testing equipment that supports the GOOSE protocol (PETOM 61850. Omicron CMC). It is important to note that all checks can be carried out without disrupting pre-established connections between secondary equipment (relay protection devices, switches, etc.), since data exchange is carried out over the Ethernet network. When exchanging discrete signals between relay protection devices in the traditional way (by applying voltage to the discrete input of the receiving device when closing the output contact of the device transmitting data), on the contrary, it is often necessary to break the connections between the secondary equipment for inclusion in the circuit of test installations in order to check the correctness of the electrical connections and transmission of corresponding discrete signals. Thus, the GOOSE protocol provides for a whole range of measures aimed at ensuring the necessary characteristics for speed and reliability when transmitting critical signals. The use of this protocol in combination with the correct design and parameterization of the information network and relay protection devices allows, in some cases, to abandon the use of copper circuits for signal transmission, while ensuring the required level of reliability and performance.

#MMS, #GOOSE, #SV, #870-104, #event, #protocol, #exchange

The International Electrotechnical Commission (IEC) is the primary international standardization organization for electrical, electronic and all related technologies, including the development and production of temperature sensors. The IEC was founded in London in 1906. The first president of the IEC was the famous British scientist Lord Kelvin. It includes representatives of 82 countries (60 countries are full members, 22 countries are associate members). Russia, Ukraine and Belarus are full members of the IEC. Representatives of the Tax Code of the Russian Federation are members of many technical committees and working groups of the IEC. Standards for temperature sensors are developed mainly within the framework of TK 65B/RG5 (SC 65B - Measurement and control devices , WG5 - Temperature sensors and instruments). On the basis of the Tax Code of the Russian Federation, the IEC has created the Russian Group of Experts on Temperature (RGE), whose task is to actively participate in the development of IEC temperature standards. Details are in the RGE section. All information on current and newly developed IEC standards is obtained from the IEC portal: www.iec.ch

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The main set of chapters of the IEC 61850 standard, first edition, was published in 2002 - 2003. Later in 2003 - 2005 The remaining chapters of the first edition were published. In total, the first edition consisted of 14 documents. Later, some of the chapters were revised and supplemented, and some documents were added to the standard. The current edition of the standard already consists of 19 documents, a list of which is given below.

• IEC/TR 61850-1 ed1.0
• IEC/TS 61850-2 ed1.0
• IEC 61850-3 ed1.0
• IEC 61850-4 ed2.0
• IEC 61850-5 ed1.0
• IEC 61850-6 ed2.0
• IEC 61850-7-1 ed2.0
• IEC 61850-7-2 ed2.0
• IEC 61850-7-3 ed2.0
• IEC 61850-7-4 ed2.0
• IEC 61850-7-410 ed1.0
• IEC 61850-7-420 ed1.0
• IEC/TR 61850-7-510 ed1.0
• IEC 61850-8-1 ed2.0
• IEC 61850-9-2 ed2.0
• IEC 61850-10 ed1.0
• IEC/TS 61850-80-1 ed1.0
• IEC/TR 61850-90-1 ed1.0
• IEC/TR 61850-90-5 ed1.0

Let's take a closer look at the structure of the standard and its constituent documents. But first of all, let's define the terminology according to which documents are designated.

Types of IEC documents

The International Electrotechnical Commission distinguishes the following types of documents:

• International Standard (IS) – International Standard
• Technical Specification (TS) - Technical requirements
• Technical Report (TR) – Technical report

International Standard (IS)

An international standard is a standard formally adopted by the International Organization for Standardization and officially published. The definition given in all IEC documents is “A normative document, developed in accordance with approval procedures, which has been adopted by the members of the IEC National Committees of the responsible technical committee in accordance with Chapter 1 of the ISO/IEC Directives.

There are two conditions for the adoption of an international standard:

1. Two-thirds of the current members of a technical committee or subcommittee vote to adopt the standard
2. No more than one quarter of the total number of votes was cast against the adoption of the standard.

Technical Requirements (TS)

Specifications are often published when a standard is under development or when the necessary agreement has not been achieved for formal adoption of an international standard.

The specifications approach the International Standard in detail and completeness, but have not yet gone through all stages of approval because agreement has not been reached or because standardization is considered premature.

The technical requirements are similar to the International Standard and are a normative document developed in accordance with approval procedures. Technical requirements are approved by a two-thirds vote of the current members of the IEC Technical Committee or Subcommittee.

Technical Report (TR)

A technical report contains information other than that usually published in international standards, for example, data obtained from studies conducted among national committees, the results of the work of other international organizations, or data on advanced technologies obtained from national committees and relevant to the subject of the standard.

Technical reports are purely informative and do not act as regulatory documents.

Approval of the technical report is carried out by a simple majority vote of the current members of the IEC technical committee or subcommittee.

Published chapters of IEC 61850

Let us consider the contents of the chapters of the standard in order, as well as the documents being developed.

IEC/TR 61850-1 ed. 1.0 Introduction and general provisions

The first chapter of the standard is issued in the form of a technical report and serves as an introduction to the IEC 61850 series of standards. The chapter describes the basic principles underlying an automation system operating in accordance with IEC 61850. The first chapter of the standard defines a three-level automation system architecture, including process level, level connections and station level. Initially, the standard defined only an automation system within one object and connections between several substations were not included in the model. Later the model was expanded in Fig. Figure 1 shows the architecture of the communication system described by the second edition of the standard, which also provides for communications between substations (see Fig. 1). Within each of the levels, as well as between levels, the structure of information exchange is described.

Rice. 1. Communication system architecture.

The list of interfaces and their purposes are also given in the first chapter of the standard and described in Table 1.

Table 1 – Interface Definitions

№	Interface
1	Exchange of protection function signals between bay and station levels
2	Exchange of protection function signals between the connection level of one object and the connection level of an adjacent object
3	Data exchange within the connection level
4	Transmission of instantaneous current and voltage values ​​from measuring transducers (process level) to bay level devices
5	Signal exchange between process and bay level equipment control functions
6	Exchange of control function signals between bay level and station level
7	Data exchange between the station level and the engineer’s remote workstation
8	Direct data exchange between bays, in particular for the implementation of high-speed functions such as online blocking
9	Data exchange within the station level
10	Exchange of control function signals between the station level and the remote control center
11	Exchange of control function signals between connection levels of two different objects, for example, discrete signals for implementing operational blocking or other automation

In addition, the first chapter of IEC 61850 describes for the first time:

• data modeling concept;
• concept of data naming with representation of logical nodes, objects and attributes of data;
• a set of abstract communication services;
• System Configuration Description Language.

The description of the above is presented in a fairly condensed form and in the first chapter is intended for informational purposes only.

IEC/TS 61850-2 ed. 1.0 Terms and definitions

The second chapter of the standard contains a glossary of terms, abbreviations and abbreviations used in the context of substation automation in the IEC 61850 series of standards. The chapter is approved in the format of Technical Requirements.

IEC 61850-3 ed. 1.0 General requirements

The third chapter of the standard is the only chapter in the series that specifies physical hardware requirements. Among these requirements, first of all, the requirements for electromagnetic compatibility of devices, permissible operating conditions, reliability, etc. are described.

The bulk of the requirements are given in the form of references to IEC 60870-2, -4 and IEC 61000-4.

It should be noted that one of the requirements of the standard, for example, is a declaration by the manufacturer of the mathematical expectation of time to failure (MTTF), as well as a description of the methodology according to which it is calculated. Knowledge of this important parameter will allow calculating the time between failures of the system as a whole.

IEC 61850-4 ed. 2.0 Systems engineering and project management

This chapter of the standard describes all entities involved in the implementation of the substation automation system and the distribution of responsibilities between them. Thus, the document describes the following participants: the customer in the form of an electric power company, a design organization or designer, an installation and commissioning organization and a manufacturer of equipment and software tools.

The document also describes the basic principles of project execution, commissioning and testing. In addition, the concept of distributing various functions between software and hardware tools is given. More detailed information on this part is given in chapter six.

IEC 61850-5 ed. 1.0 Requirements for functions and devices regarding data transmission X

The fifth chapter of the standard details the conceptual principles of dividing the automation system into levels described in the first chapter, and also describes the concept of using logical nodes and proposes their classification in accordance with the functional purpose. In addition, the chapter provides examples of interaction diagrams of various logical nodes when implementing a number of functions RZA.

The terms “interoperability” and “interchangeability” are also mentioned here. At the same time, emphasis is placed on the fact that the standard does not imply interchangeability of devices; its purpose is to ensure functional compatibility of devices. These two concepts are often confused when discussing the IEC 61850 standard.

An important part of this chapter is also a description of the system performance requirements in terms of acceptable time delays.

The standard normalizes the total signal transmission time, which consists of three components:

• the time of encoding the signal received from the internal function by the communication interface,
• signal transmission time over the communication network,
• the time of decoding data received from the communication network and transmitting it to the function of another device.

The total signal transmission time will be related to the total transmission time of similar signals using analog interfaces (for example, discrete relay inputs/outputs or analog current and voltage circuit inputs). The fifth chapter of the standard normalizes permissible time delays for various types of signals, including discrete signals, digitized instantaneous current and voltage values, time synchronization signals, etc.

It should also be noted that in the second edition of the fifth chapter, the official publication of which is scheduled for autumn 2012, a new system of performance classes has been introduced. However, in fact, the requirements for acceptable delays in the transmission of certain types of signals have not changed.

IEC 61850-6 ed. 2.0 Configuration description language for data exchange

The sixth chapter of the standard describes the file format for describing the configurations of devices involved in data exchange according to IEC 61850. The main task of the general format is to provide the ability to configure the device with external software.

This description file format is known as Substation Configuration Language (SCL) and is based on the XML markup language generally accepted in the IT environment.

In order to define clear rules for the generation of SCL format files, as well as ease of verification of the correctness of their composition, an XSD scheme was developed, which is also described in Chapter 6 and is an integral part of the IEC 61850 standard.

The original version of the diagram was published with the first edition of Chapter 6 in 2007. Later, the scheme underwent a number of changes, related, in particular, to error corrections and a number of additions to SCL files, and in 2009 its new edition was published.

Thus, there are now two editions of the scheme: 2007 and 2009, usually referred to as the “first” and “second” editions. Despite the differences between them, it is expected that devices that are compatible with the “second edition” should be backward compatible with the “first edition” devices. In practice, this does not always happen, unfortunately. However, this does not prevent communication between devices by assigning each device a configuration using the manufacturer’s software.

IEC 61850-7 Basic communication structure

The IEC 61850 standard defines not only data transfer protocols, but also the semantics with which this data is described. The seventh section of the standard describes approaches to modeling systems and data in the form of classes. All parts included in the seventh section are interconnected with each other, as well as with chapters 5, 6, 8 and 9.

IEC 61850-7-1 ed. 2.0 Basic Communication Structure – Principles and Models

Section 7-1 of the standard introduces basic methods for modeling systems and data, presents principles for organizing data transmission and information models used in other parts of IEC 61850-7.

This chapter describes the principle of representing a physical device with all the functions it contains as a set of logical devices, which, in turn, consist of a set of logical nodes. The technology for grouping data into data sets and then assigning this data to communication services is also described.

This chapter also describes the principles of data transfer carried out using the client-server or publisher-subscriber technology. However, it should be noted that this chapter, like the entire section 7, describes only the principles and does not describe the assignment of signals to specific communication protocols.

IEC 61850-7-2 ed. 2.0 Basic communications structure – Abstract Communications Interface (ACSI)

Chapter 7-2 describes the so-called “abstract communication interface” for power plant automation systems.

The chapter describes the class diagram and data transfer services. A conceptual diagram of class connections is shown in Fig. 2. A more detailed description of this scheme will be given in one of the future publications under the heading.

Rice. 2. Class connection diagram.

The chapter provides a detailed description of the properties of each of the classes, and the data transfer services section presents the connection of these classes with possible services, such as reports, event logs, reading/writing data or files, multicasting and instantaneous value transfer.

Thus, the chapter in abstract form describes in detail the entire structure of communications, starting from the description of the data itself, as a class, and ending with the services for transmitting it. However, as mentioned above, all this description is given only in abstract form.

IEC 61850-7-3 ed. 2.0 Basic Communication Structure – General Data Classes

As can be seen from Fig. 2, each data class (DATA) includes one or more data attributes (DataAttribute). Each data attribute is, in turn, described by a specific data attribute class. Chapter 7-3 describes all possible data classes and data attribute classes.

Data classes include several groups:

• Classes for describing state information
• Classes for describing measured values
• Classes for control signals
• Classes for discrete parameters
• Classes for continuous parameters
• Classes for Descriptive Data

The described classes allow you to model all kinds of data within the framework of the PS automation system for the purpose of further exchange of this data between devices and systems.

Compared to the first chapter, the second took into account adjustments in accordance with Tissues, in addition, new classes of data and attributes were added that were required in new information models built in accordance with the requirements of the standard and used outside of substation automation systems.

IEC 61850-7-4 ed. 2.0 Basic Communication Structure – Logical Node and Data Object Classes

This chapter of the standard describes the information model of devices and functions related to substations. In particular, it defines the names of logical nodes and data for data transfer between devices, and also determines the relationship of logical nodes and data.

The logical node and data names defined in Chapter 7-4 are part of the class model proposed in Chapter 7-1 and defined in Chapter 7-2. The names defined in this document are used to construct hierarchical references to objects for the purpose of further reference to data in communications. This chapter also applies the naming rules defined in Chapter 7-2.

All logical node classes have names consisting of four letters, and the first letter in the name of a logical node class indicates the group to which it belongs (see Table 3).

Table 3 – List of logical node groups

Group indicator	Group name
A	Automatic control
B	Reserved
C	Dispatch control
D	Distributed Energy Sources
E	Reserved
F	Function blocks
G	General Features
H	Hydropower
I	Interfaces and archiving
J	Reserved
K	Mechanical and non-electrical equipment
L	System logical nodes
M	Accounting and measurements
N	Reserved
O	Reserved
P	Protection functions
Q	Electrical energy quality control
R	Protection functions
S*	Supervisory control and monitoring
T*	Instrument transformers and sensors
U	Reserved
V	Reserved
W	Wind power
X*	Switching devices
Y*	Power transformers and related functions
Z*	Other electrical equipment
* Logical nodes of these groups exist in dedicated IEDs, provided that the process bus is used. If the process bus is not used, then the specified logical nodes correspond to I/O modules and are located in the IED, connected by copper links to the equipment and located at a higher level (for example, at the bay level) and represent the external device by its inputs and outputs (process projection).

IEC 61850-7-410, -420 and -510

The IEC 61850-7-410 and -420 standards are extensions of Chapter 7-2 and contain descriptions of logical node classes and data for hydroelectric power plants and small-scale generation.

Technical Report IEC/TR 61850-7-510 explains the use of the logical nodes defined in Chapter 7-410, as well as other documents in the IEC 61850 series, to model complex control functions in electrical power plants, including variable speed pumped storage plants.

IEC 61850-8-1 ed. 2.0 Assignment to a specific communication service – Assignment to MMS and IEC 8802-3

As noted above, section 7 of the standard describes only the fundamental mechanisms for data transfer. Chapter 8-1, in turn, describes methods for exchanging information over local networks by assigning abstract communication services (ACSI) to the MMS protocol and ISO/IEC 8802-3 frames.

Chapter 8-1 describes protocols for both latency-critical and non-latency-critical data exchanges.

Services and the MMS protocol operate on the full OSI model on top of the TCP stack, due to which data transmission over this protocol is carried out with relatively large time delays, so the use of the MMS protocol allows you to solve data transfer tasks for which the delay is not critical. For example, this protocol can be used to transmit telecontrol commands, collect telemetering and telesignaling data, and send reports and logs from remote devices.

In addition to the MMS protocol, Chapter 8-1 describes the purpose of data that requires fast data transfer. The semantics of this protocol are defined in IEC 61850-7-2. Chapter 8-1 describes the protocol syntax, defines the purpose of ISO/IEC 8802-3 data frames, and defines procedures related to the use of ISO/IEC 8802-3. This protocol is known to specialists as the GOOSE protocol. Due to the fact that data in this protocol is assigned directly to the Ethernet frame, bypassing the OSI model and bypassing the TCP stack, data transmission in it is carried out with noticeably lower delays compared to MMS. Thanks to this, GOOSE can be used to transmit circuit breaker tripping commands and similar fast signals.

IEC 61850-9-1 ed. 1.0 Assignment to a specific communication service – Transmission of instantaneous values ​​via the serial interface

This chapter described methods for transmitting instantaneous values ​​by assigning data to a serial interface according to IEC 60044-8. However, in 2012, this chapter was removed from the IEC 61850 series of standards and is no longer supported.

IEC 61850-9-2 ed. 2.0 Assignment to a specific communication service – Transmission of instantaneous values ​​via the IEC 8802-3 interface

Chapter 9-2 of the IEC 61850 standard describes methods for transmitting instantaneous values ​​from CTs and VTs via the IEC 8802-3 interface, that is, they will determine the assignment of the class of service for transmitting instantaneous values ​​from measuring CTs and VTs IEC 61850-7-2 to the ISO/IEC 8802- protocol 3.

This chapter of the standard applies to current and voltage measuring transformers with a digital interface, process bus interface devices and IEDs with the ability to receive data from CTs and VTs in digital form.

In fact, this chapter describes the format of an Ethernet frame depending on what data is assigned to it, that is, it will determine its relationship with the data class according to IEC 61850-7-2 and description according to IEC 61850-6.

The first edition of Chapter 9-2 did not provide for such important points as provision of redundancy. In the second edition, these shortcomings were taken into account, and therefore the 9-2 frame format was supplemented with fields for PRP or HSR reservation protocol labels.

Specification IEC 61850-9-2LE

The first edition of the IEC 61850-9-2 standard was published in 2004, however, the lack of clearly defined requirements for sampling rates of instantaneous values ​​and the composition of the transmitted packet could lead to potential incompatibility between solutions from different manufacturers. In order to facilitate the development of compatible solutions based on the IEC 61850-9-2 protocol, the UCA user group, in addition to the standard, also developed a specification (referred to as “9-2LE”), which specified the composition of the transmitted data packet and defined two standard frequencies: 80 and 256 samples per power frequency period, that is, it actually established standard requirements for the IEC 61850-9-2 interface for all devices.

The appearance of this specification along with the document significantly influenced the intensity of penetration of the protocol into equipment. However, it should be understood that this document is not a standard in itself, but only specifies the requirements of the standard, that is, it represents a specification of the standard.

IEC 61850-10 ed. 1.0 Compliance check

Chapter ten of the standard defines procedures for testing the compliance of devices and software with the requirements of the standard and specifications.

In particular, the chapter defines a methodology for checking the compliance of actual delays during the formation and processing of message packets with the stated parameters and requirements of the standard.

IEC/TS 61850-80-1 ed. 1.0 Guidance on transferring information from a common data class model using IEC 60870-5-101 or IEC 60870-5-104

The document describes the assignment of the general IEC 61850 data classes to the IEC 60870-5-101 and -104 protocols.

IEC/TR 61850-90-1 ed. 1.0 Use of IEC 61850 for communication between substations

Initially, the IEC 61850 standard was designed to ensure data transmission between devices only within a substation. Subsequently, the proposed concept found application in other systems in the electric power industry. In this way, the IEC 61850 standard can become the basis for global standardization of data networks.

Existing and developing protection and automation functions require the ability to transfer data not only within, but also between substations; therefore, it is necessary to expand the scope of the standard for data exchange between substations.

The IEC 61850 standard provides the basic tools, but a number of changes are required to standardize communication protocols between objects. Technical Report 90-1 provides an overview of the various aspects that must be taken into account when using IEC 61850 for data exchange between substations. Areas where expansion of existing standard documents is required will later be included in the current versions of the standard chapters.

One example of a needed extension would be the transmission of GOOSE messages between objects. Currently, GOOSE messages can only be transmitted in broadcast mode to all devices included in the local network, but they cannot pass through network gateways. Chapter 90-1 describes the principles of establishing tunnels for transmitting GOOSE messages between different local area networks of objects.

IEC/TR 61850-90-5 ed. 1.0 Use of IEC 61850 for transmission of data from synchronized vector measurement devices in accordance with IEEE C37.118

The main purpose of Technical Report 90-5 was to propose a method for transferring synchronized phasor measurements between a PMU and a control system. Data described by the IEEE C37.118-2005 standard is transmitted in accordance with the technologies provided by IEC 61850.

However, in addition to the initial tasks, this report also presents profiles for routing GOOSE (IEC 61850-8-1) and SV (IEC 61850-9-2) packets.

IEC 61850 documents under development

In addition to the documents reviewed, 21 more documents are currently being developed by working group 10, as well as related working groups, which will be part of the IEC 61850 series of standards.

Most of these documents will be published in the form of technical reports:

• IEC/TR 61850-7-5. Using information models of substation automation systems.
• IEC/TR 61850-7-500. Using logical nodes to model the functions of substation automation systems.
• IEC/TR 61850-7-520. Using logical nodes of small generation objects.
• IEC/TR 61850-8-2. Assignment to web services.
• IEC/TR 61850-10-2. Tests for functional compatibility of hydroelectric power plant equipment.
• IEC/TR 61850-90-2. Use of the IEC 61850 standard to organize communication between substations and control centers.
• IEC/TR 61850-90-3. Use of IEC 61850 in equipment condition monitoring systems.
• IEC/TR 61850-90-4. Guidelines for the engineering of communication systems in substations.
• IEC/TR 61850-90-6. Using IEC 61850 for automation of distribution networks.
• IEC/TR 61850-90-7. Object models for power plants based on photocells, batteries and other objects using inverters.
• IEC/TR 61850-90-8. Object models for electric vehicles.
• IEC/TR 61850-90-9. Object models for batteries.
• IEC/TR 61850-90-10. Object models for systems for planning operating modes of small-scale generation facilities.
• IEC/TR 61850-90-11 Modeling of freely programmable logic.
• IEC/TR 61850-90-12. Guidelines for distributed communications network engineering.
• IEC/TR 61850-90-13. Expanding the composition of logical nodes and data objects for modeling equipment of gas turbine and steam turbine plants.
• IEC/TR 61850-90-14. Using the IEC 61850 standard to model FACTS equipment.
• IEC/TR 61850-90-15. Hierarchical model of small generation objects.
• IEC/TR 61850-100-1. Functional testing of systems operating under the terms of the IEC 61850 standard.

Conclusion

The IEC 61850 standard, originally developed for use within substation automation systems, is gradually beginning to extend to automation systems for other power system assets, as evidenced by a number of recently published and even more upcoming documents. New equipment and new technologies developing “under the banner” of intellectualization of the power system are accompanied by their description in the context of the IEC 61850 standard, while the development/modernization of other standards similar in purpose is not carried out. This allows us to make a bold assumption that every year the standard will become more widespread in practice.

Bibliography

1. http://www.iec.ch/members_experts/refdocs/governing.htm
2. http://tissue.iec61850.com
3. Implementation Guideline for Digital Interface to Instrument Transformers Using IEC 61850-9-2. UCA Internation Users Group. Modification Index R2-1. http://iec61850.ucaiug.org/implementation%20guidelines/digif_spec_9-2le_r2-1_040707-cb.pdf