Model Based Testing and Diagnosis of IEC 61850 Systems

Author: Iony Patriota de Siqueira, Chesf, Brazil

This article reviews this method and describes its use for fault diagnosing through a proof-of-concept prototype developed in a research project. With this tool, fault diagnosing in Substation Automation Systems (SAS) is done using a model-based approach whereby an object oriented model of the system is provided that can be simulated while faults are identified and pinpointed. Testing is also performed in an object oriented way, conducted by following a test script according to the scheme proposed by Cigre WG B5.32. In addition, fault diagnosis may be performed by correlating the test results with the model architecture.

This article reports the results of a Brazilian research project jointly sponsored by CHESF (Companhia Hidro Elétrica do São Francisco) and ANEEL (Agência Nacional de Energia Elétrica), and conducted by UFCG (Universidade Federal da Paraiba), to develop a proof-of-concept software tool that enables automation engineers to build, run and debug functional tests for IEC 61850-based systems. The testing is based on the specification produced by WG B5.32. An extension of this work is being developed to allow diagnosis, using the same tool.

Automation Model

A simple example will illustrate the test method proposed by Cigre, taken from the work done by WG B5.32. Only a brief sketch of a test scenario will be given due to space restrictions. Please refer to the full WG B5.32 technical brochure for details. The approach is based on UML, text and XML formats, used to specify Functional Use Cases and other UML artifacts. Consider the SAS for a simple one-line diagram of a transformer bay in a substation shown in Figure 1, taken from WG B5.32 Technical Brochure, with the corresponding logical nodes defined by IEC 61850. This figure uses a UML communication diagram to specify the message types exchanged by the logical nodes of the SAS.

This type of diagram can be part of a functional specification of an SAS system, not covered by current version of IEC 61850, that includes a Functional Implementation Conformance Statements (FICS), in a format proposed by Cigre WG B5.32 shown in Table 1.

In addition, other UML diagrams may be used for functional specification. For example, a UML sequence diagram is shown in Figure 2 that may be part of the FICS document. In this Figure the numbers shown are PICOM types (12 = Operated, 22 = Trip, etc.). The left-hand side of the figure also shows the performance requirements as UML time delay restrictions.

Further details about the SAS could be included in a UML deployment diagram, showing the physical distribution of logical nodes in servers, their labels, network addresses, etc., as shown in Figure 3.

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