ECAI 2017 - International Conference – 9th Edition Electronics, Computers and Artificial Intelligence 29 June -01 July, 2017, Targoviste, ROMÂNIA
A Practical Approach to IEC 61850 Standard for Automation, Protection and Control of Substations Balduino Estison Mugilila Camachi, Oana Chenaru, Loretta Ichim, Dan Popescu Faculty of Automatic Control and Computer Science University Politehnica of Bucharest Bucharest, Romania
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[email protected] Abstract – This article discusses the new IEC61850 Standard for Substation Automation, considering its functionalities, requirements, and definitions. It provides an application-oriented approach through the capabilities that the new tools and Intelligent Electronic Devices (IEDs) allow. The work highlights the importance of modern IEDs, emphasizing the main characteristics that these components must possess to meet the requirements of IEC 61850. Based on the new possibilities that the development of the norm has brought, the work presents the potential functionalities discussed in recent articles in the main events of the community, and highlights how to perform these tasks and use the resources now available. Through the implementation of Logical Nodes (LNs), GOOSE messages (Generic Object-Oriented Substation Event) and other tools, the authors approach the logical schemes of interlocking, and transfers or locks execution. All features, functionalities and data presented in the article are based on results obtained in a real application from the 110/ 20kV Babadag 1 Wind Farm. Keywords-IEC 61850; Substation Systems; protection; control; Modbus
I.
Automation
INTRODUCTION
IEC 61850 was developed to standardize the use of LAN for protection and automation, allowing the provision of relevant information to various users, such as regional management, maintenance management and operations, engineering protection. [1]. Because of the benefits of this technological change, there were notable evolutions in the protection relays, in the Acquisition and Control Units (ACU) and in other digital equipment such as meters and oscillographs. They became intelligent devices, generically called Intelligent Electronic Devices (IEDs). These devices, besides adding more resources to the tasks of protection, measurement, oscillography, are also able to participate in the various functions of supervision, control and automation used commonly in a substation [1].
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As a relatively recent standard, IEC 61850 is still under development, with the combined efforts of manufacturers, research institutions and international regulatory forms. Currently, this standard has the following main characteristics [2]: •
Represents a set of protocols and criteria;
•
It is being adopted in many countries;
•
Corresponds to the state of the art of digital technology in substation automation;
•
Enables a complete integration between the several intelligent digital devices using highspeed, high levels of reliability in Local Area Network (LAN), networks based on Ethernet technology [3];
•
Enables the sharing of information with widely tested technologies such as the Extensible Mark-up Language (XML) language, making it easier to deploy automation functions and the support with operation and maintenance.
IEC 61850 defines and offers much more than just a protocol. Several inherent features in IEC 61850communication standard provide various opportunities and benefits over legacy substation communication protocols such as IEC 60870-5, DNP3.0, and Modbus. Some of the benefits offered by IEC 61850 include: simple and cost effective substation architecture, future proof standard, benefits of switched Ethernet technology, high level engineering support based on SCL, standardized data modeling and high level communication services. The IEC 61850 standard solved the problem of scalable system expansions, ensuring interoperability between different manufacturers' IEDs, eliminating the dependence on a single vendor, and drastically reducing the deployment and shutdown times required [1]. In addition to changing the technical concept of the systems operation, it introduces new benefits at various stages of a system development, as discussed below [4]:
Balduino Camachi, Oana Chenaru, Loretta Ichim, Dan Popescu •
Project: the use of integrated specification tools and standardized design elements reduces the effort involved in the development of Substation Automation Systems with the added benefit of automated documentation processes [4];
•
Deployment: automatic generation equipment configuration files;
•
Construction and installation: significant reduction of electric cables with a consequent reduction of connection errors of these cables;
•
Commissioning: ability to model and simulate the entire system of a substation, reducing field testing;
•
Documentation: Provides digitized access to the documentation, without the need to continually recreate documents and reduce problems with different databases.
of
It should be emphasized that some aspects of substation automation are beyond the scope of IEC 61850 because they depend on the development characteristic of each manufacturer and each user [4]. The most important characteristics are the following: internal IED algorithms, application functionalities, topology of communication networks, IED configuration methods and methods of analysis and diagnosis [1]. II.
does not operate in the transport layer of the Open Systems Interconnection (OSI) frame, the acknowledgment of the received messages is not performed. Thus, in order to increase the probability that other devices receive the data, the IEDs send a GOOSE message with an event, repeatedly according to the times T1, T2 and T3 shown in Fig. 2 [8].
Figure 1. Data Structure defined by the standard [7]
DESCRIPTION OF THE STANDARD METHODOLOGY
A. General Requirements The general requirements of the communication network are defined in the standard IEC 61850-3, with emphasis on quality requirements. These requirements, represented by reliability, availability, maintenance, security, data integrity, are defined in detail along with other requirements which apply to the communication systems that are used for monitoring and controlling processes within the substation [3]. B. The structure of the data The standard IEC 61850 defined the format of the information, and the transport of the data uses TCP / IP network technology, widespread and used today. IEC 61850 does not use numbers or numerical indices for addressing its real-time data objects, but names [3]. As in the example of Fig. 1, which represents the state of a circuit breaker, the points are classified hierarchically in [6]: Physical Device, Logical Device, Logical Nodes, Data Objects and Data Attributes. C. IEC 61850 messaging services The so-called Generic Object Oriented Substation Event (GOOSE) communication service provides the user with a high-speed control messaging capability. This service allows transmitting messages with states, controls and analog measurements through the network for use by other devices in horizontal communications - peer-to-peer [1]. Because GOOSE
Figure 2. GOOSE Communication [8]
The transmission times from Fig. 2 are: a) T0: GOOSE retransmission period under stable conditions; b) T (0): moment when GOOSE retransmission interrupted by an event; c) T1: retransmission of the event in short periods; d) T2 and T3: retransmission of the event in short periods until reaching stability. The GOOSE model uses the data that is published in a grouped form in data sets, as shown in Fig. 3. Many data, such as analog, binary or integer values, and their quality attributes, can be used to compose the data sets. Each sent GOOSE message also includes communication parameters such as VLAN ID, priority defined by the 802.1Q standard, and a Multicast Media Access Control (MAC) address in a single packet. This six-byte hexadecimal address called Multicast has the following recommendation as the standard: a) The first three octets are defined by the IEEE as 01-0C-CD; b) The forth octet must be 01 for GOOSE, 02 for Generic Substation Status Event (GSSE) and 04 for sampled values;
A Practical Approach to IEC 61850 Standard for Automation, Protection, and Control of Substations c) The last two octets shall be used individually by the interval defined in table 1.
the exchange of database configuration data between different tools that can be provided by different manufacturers [11]. Four different types of SCL files are used in the design phase to define the substation architecture, as shown in Fig. 4 [7]: a) System Specification Description (SSD): Power System functions;
Figure 3. GOOSE message published in data sets [9]
In Table I, the ranges of Multicast addresses are displayed. TABLE I.
TABLE I. MULTICASTING RECOMMENDED BY THE STANDARD [9]
Service
Start
End
GOOSE
01-0C-CD-01-00-00
01-0C-CD-01-01-FF
GSSE
01-0C-CD-02-00-00
01-0C-CD-02-01-FF
Sampled Values
01-0C-CD-04-00-00
01-0C-CD-04-01-FF
The main features of the GOOSE message are: a) Publisher/subscriber; b) Multiple consumers require multicast MAC addresses; c) Does not use IP, so there is no network layer or transport layer of the OSI model; d) Is not routable; e) Multicast for many consumers within the LAN only. In addition to the GOOSE priority messaging service, IEC 61850 also provides a vertical client / server communication service called MMS that provides real-time data transfer services at the application layer within a substation LAN. MMS was developed as an independent data exchange protocol for industrial networks in the 1980s and was standardized by ISO 9506. Features of the MMS protocol: Client/Server, a specific consumer requires unicast MAC address, uses IP therefore, provides transport layer and network layer of the OSI model and MMS is routable for LAN or WAN consumers [3]. III.
IMPLEMENTATION ON A TEST PLATFORM
A. Commnunication arhitecture and configuration Apart from the definition in the standard of a formalized dictionary of names and a hierarchical structure of objects, another important feature introduced by IEC 61850 was the definition of a standardized file format, derived from the Common Information Model (CIM) specification. This is used in the exchange of information between the equipment and systems configuration tools of different manufacturers. Substation Configuration Language (SCL) is an XML-based configuration language used to support
b) Substation Configuration Description (SCD): complete definition of the substation, with communication network architecture; c) IED Capability Description (ICD): describes the data supported by a type of IED; d) Configured IED Description (CID): Describes the configuration of a specific IED.
Figure 4. Files standardized by IEC 61850 [7]
The ICD file describes the capabilities of an IED, including information about Logical Nodes (LN) and GOOSE definition. The SSD file describes the singleline diagram of the substation and the required LN [12] [3]. The SCD file contains information about all IEDs, communications configuration data, and a substation description. The CID file, which can exist in multiple instances in a substation architecture, describes a single IED instantiated within the project, and includes address information [12]. B. Difference between Master/ Slave and Client/ Server. When combining process automation with Industrial Ethernet, engineers need to identify the correct approach to data transmission. Master/ Slave, is based on a Master sending a request to the Slave, while the Slave carries out that command. If there is a command to open a Circuit Breaker (CB) the slave will do it. If the command is to send back the position of the CB, the slave will then send that information back. Obviously, it can have multiple Masters but it can only carry out the commands of one Master at a time [13] [16], i.e. each Master would individually have to ask the Slave what position the CB is in. If a protection operation trips the CB, the only way a Master/ Slave would know about it is if the Master, by chance, asks the Slave what is the CB position whilst the CB is still open. If in the meantime there has been an automatic reclose before the Master polls for the status, the next request from the Master will result in the Slave simply sending back that the CB is (apparently still) closed and the event of the CB opening and reclosing is missed. The Master would have to poll other information to eventually detect that a protection trip occurred followed by the reclosure.
Balduino Camachi, Oana Chenaru, Loretta Ichim, Dan Popescu In a Client/ Server architecture, the Client initiates the communication. In addition to this, the Server can automatically send information to the Clients. The Server can be configured to send a Report to the Client(s) every time the CB position changes noting the Report can be configured to be sent to multiple Clients.
your slave device from supplier. Data contained with any open document is accessible to the master application. Same user interface as Modbus Poll. Support function 01, 02, 03, 04, 05, 06, 15, 16, 22 and 23 [16].
In this case, for example, if an auto reclose follows the protection trip, the Server would Report the CB opening (because of the protection operation) automatically to the all the configured Client(s) who are supposed to know about it, and also Report the CB closing again to the Client(s). The only possibility of the Clients not knowing all operations is if the Report doesn't arrive at the Client(s). Hence, we have two types of Client/Server Reports - Unbuffered and Buffered. Client/ Server Unbuffered Reports can be used when the Server just "throws" the Report to the communications network without knowing if the message could or does get to the required Clients. If the communication is down the message will be lost. Client/ Server Buffered Reports means the Server effectively verifies the message gets through to the Client. If it doesn't get verified as reaching the Client, the Server puts the message in a buffer and keeps retrying to send it until it is verified (or it is overwritten as a buffer full). To perform the tests we needed the following equipment and software: •
•
•
UC 500 (Unidade Central) is a Central Unit from EFACEC, targeted to be used in the CLP 500 platform. The general configuration of the UC 500 device includes the configuration of: data points, controls, synchronism module, watchdog, redundancy, and generic device parameters, as well as the HMI and the several communications protocols. The HMI includes alarms and trends management, mimics, and event logs [14]. Automation Studio 3.0 Rev.2 - is a userinterface software tool for configuring and managing protection, automation and control devices and systems such as substation automation systems (SAS) or similar systems. This tool features object oriented device configuration and management, relies heavily on an integrated and configurable windowing environment, featuring systematic use of copy/paste, drag-and-drop and context menus, allowing intuitive handling of definitions [15]. Modbus Slave allows simulating up to 32 slave devices in 32 windows. Speed up your PLC programming with this simulation tool. Start programming and test before you receive
Figure 6. Automation Studio
IV.
EXPERIMENTAL RESULTS
The experimental results are based on a comparison between IEC 61850 protocol and Modbus TCP/IP protocol. Modbus is an open protocol widely used in process control and automation. The protocol is available in many devices like sensors, process controllers, and actuation elements. Modbus TCP/IP is defined as a Master and Slave protocol, meaning a device operating as master will poll one or more devices operating as slaves. A slave will send data only when a master requested it. The protocol uses a standard frame format, storing information on the slave identification number, requested function, data quantity and storage address. Data transmission is not encrypted, making it easy to analyze and debug communication status. In Modbus TCP, the data frame is encapsulated in the TCP/IP frame, making it compatible with Ethernet communication networks. IEC 61850 protocol supports both Server and Client implementations. This increases the flexibility in adapting to an application particularities. The major differences between these protocols are the illustrated in Table II. TABLE II.
TABLE II. COMPARISON OF THE ANALYZED PROTOCOLS
Indications
IEC 61850
Command
Data Transmission Process bus Fault Records Inter-operability
Event
Modbus Without time stamp Without time stamp On request × × ×
A. Evaluation of the Modbus communication The tests were made at 110/20kV Babadag 1 Wind Farm, located in Tulcea County, Romania.
A Practical Approach to IEC 61850 Standard for Automation, Protection, and Control of Substations
Figure 7. Modbus trace
The Modbus Simulator was configured with function 03x Holding Register, the first 10 addresses 40001 – 40010 were configured as 16 bits unsigned integer and each given the value 0, these addresses were maped in the UC 500 on analogues ANL_01 – ANL_10 and the 40001 – 40010 addresses were interrogated on a 10sec cycle (Fig. 7). The value updates were made on a the simulator (Fig. 8 - 9), and can be also seen on the entity viewer from the UC500 on Fig. 10. At 15:25:16 address 40003 was given the value 2. At 15:26:06 address 40004 was given the value 3; At 15:26:31 address 40008 was given the value 7.
Figure 9. Address 40008 simulation
The corresponding analogues entities were updated correctly as can be seen in Fig. 11 (field Tags, Last Update Time and Value).
Figure 10. Entity Viewer – UC500
Figure 8. Address 40003 simulation
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Balduino Camachi, Oana Chenaru, Loretta Ichim, Dan Popescu
Figure 11. Scanner IEC 61850 Trace
B. Evaluation of the IEC 61850 communication The tests were made by tracking the data from the IEC device, in this case I used the Scanner IEC 61850 Trace Windows provided by one of the many processes from the UC500. One of the great advantages of using the IEC 61850 is the possibility of using the same physical network to trace the data from various services. By checking through the trace, messages of different frames are transiting in the same physical network. As we saw in the Modbus protocol, this versatility is not applicable in other protocols, which requires the physical network of communication exclusively for the protocol. We can see that the IEC 61850 communication is almost complete, the time difference of the information received is very short, as in the case of Modbus protocol is only made when it is requested, the IEC 61850 is not necessary to be interrogated in order to obtain information. I.
CONCLUSIONS
This paper presents and evaluates communication technologies that can be used in power substations, in the areas of protection, supervision, and operation. The IEC 61850 protocol, used as a Server/ Client configuration, showed better transmission times and a behavior better suited for critical applications. It can send information in a short time both on event and on request. Modbus, as a slave device, cannot volunteer information; it must wait to be asked for it. The analysis showed that, in case of applications considering high emergency events, use of Modbus protocol is not suitable. As future work, we propose to conduct an analysis that will evaluate the economic impact of the implementation of the IEC 61850 Standard for substations, whether new applications, or updates to existing stations. We also want to evaluate the case of interconnecting devices from two or more different manufacturers, in order to remove the fences and limitations identified in this work regarding interoperability. This should test if it is possible to replace an IED of a Manufacturer A with an equivalent functionality equivalent with a
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Manufacturer B IED in a substation, without changing the other elements of the system. V. [1]
[2]
[3] [4]
[5] [6] [7] [8] [9]
[10]
[11]
[12]
[13] [14] [15] [16]
REFERENCES
J.-C. Tan, V. Green, and J. Ciufo, “Testing IEC61850 based Multi-Vendor Substation Automation Systems for Interoperability”, Proceedings of the 2009 IEEE/PES Power Systems Conference and Exposition, Seattle, WA, USA, 2009, pp. 1-5. W. Wimmer, “IEC 61850 Edition 2 and Engineering”, 2014, available online at: http://www.pacw.org/issue/december_2014_issue/iec_61850_ edition_2_and_engineering/maintenance_testing_program_ch oices_tbm_cbm_and_pbm/complete_article/1.html Last accessed on 18/02/2017 R. E. Mackiewicz, “Overview of IEC 61850 and Benefits”, PES TD 2005/2006. IEC61850-8-1, Communication Networks and Systems in Substations Part 8-1: Specific Communication Service Mapping (SCSM) Mappings to MMS (ISO/IEC 9506-1 and ISO/IEC 9506-2) and to ISO/IEC 8802-3. Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2016 39th International Convention. K.-P. Brand, “How to Use IEC 61850 in Protection and Automation”, Electra-Cigre, October 2005. Configuration Description Language for Communication in Electrical Substation related to IEDs, First edition 2004-03. R. Pereda, I. Aguirre, J. Castellanos, and I. Garces, “Substation Automation Experiences based on the IEC 61850 GOOSE”. International Electrotechnical Comission. IEC 61850-8-1 Communication networks and systems in substation. Part 8-1: specific communication service mapping (SCSM) - Mappings to MMS (ISO 9506-1 and ISO 9506-2) and to ISO/IEC 88023. Switzerland, 2004. IEC: 2004 (E). International Electrotechnical Comission. IEC 61850-7-1 Communication networks and systems in substation. Part 7-1: Basic communication structure - Principles and models. 2.ed. Switzerland, 2011. IEC: 2004 (E). M. C. Janssen and A. Apostolov, “IEC 61850 Impact on Substation Design,” in Transmission and Distribution Conference and Exposition 2008. T&D. IEEE PES, pp. 1-7, April 2008. L. Andersson, C. Brunner and F. Engler, “Substation Automation Based on IEC 61850 with New Process-Close Technologies,” in Proc. IEEE Power Tech, Bologna, Italy, June 2003. Modicon Industrial Automation Systems, “Modicon Modbus Protocol Reference Guide”, Modicon Inc., 1996. UC500 User Manual – EFACEC – 2016 Ed.2 Automation Studio User Manual – EFACEC Rev.8.3 – July 2015 Modbus Slave application, available online at: http://www.modbustools.com
