8. СОВЕТУВАЊЕ. Охрид, септември UTILIZING IEC FOR COMMUNICATION TOWARDS CONTROL CENTRE SCADA SYSTEMS

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1 8. СОВЕТУВАЊЕ Охрид, септември Stjepan Sučić Ante Martinić KONČAR Power Plant and Electric Traction Engineering Inc., Zagreb, Croatia Juraj Havelka Faculty of electrical engineering and computing, University of Zagreb, Zagreb, Croatia UTILIZING IEC FOR COMMUNICATION TOWARDS CONTROL CENTRE SCADA SYSTEMS ABSTRACT Supervisory Control and Data Acquisition (SCADA) applications in power system control centres usually communicate with other subsystems by using some common telecontrol protocol such as IEC , IEC or DNP3. One of the major drawbacks of this approach is the lack of standardized process data semantics. This feature significantly decreases capability of streamlined configuration and maintenance of control centre SCADA systems. Majority of newly integrated substations are based on IEC standard which provides integrated process data semantics. According to common practice, substation-level process data based on IEC are mapped to some of aforementioned telecontrol protocols. This process results in several negative impacts such as inevitable loss of data semantics, introducing additional latencies in data-exchange processes and error-prone configuration. These and similar issues could be eliminated by using IEC communication at control centre level. This paper provides an outline of current standardization results related to IEC s Technical Committee 57 (TC57) efforts which aim to develop IEC based communication towards control centres. It is also shown how these features are applied in industrial practice as a functional part of PROZA NET SCADA system. Keywords: IEC , SCADA, Gateway 1 VERTICAL COMMUNICATION IN IEC SYSTEMS Vertical communication in IEC systems is used for data-exchange between intelligent electronic devices (e.g. bay controller) and applications (e.g. substation-level SCADA system). Main IEC advantage compared to other telecontrol protocols is utilization of standardized semantics for process-related data. Information model introduced by IEC is based on object-oriented design and seamless description of automated subsystem functional elements [1]. Most of the newly installed supervisory control systems is using vertical IEC communication only on substation level, while communication towards the control centres is based on using some of the common telecontrol protocols such as IEC [2], IEC [3] or DNP3 [4]. In order to represent IEC process data by using some of above-mentioned telecontrol protocols it is necessary to develop data conversion rules for protocol gateways [5]. Data conversion process introduces latencies into data-exchange process and causes inevitable loss of data semantics. These and similar issues have motivated latest series of standardization activities in order to develop adequate technical platform which will enable utilization of vertical communication towards the control centres based on IEC61850 standard. D2-054I 1/5

2 MAKO CIGRE 2013 D2-054I 2/5 2 IEC COMMUNICATION TOWARDS CONTROL CENTRES 2.1 Functional limitations of current IEC edition Current version of IEC standard defines vertical communication for data-exchange between device and application which can be applied out of Local Area Networks (LAN). This is practically the only technical precondition for communication towards control centres [6]. However, using current version of IEC standards for communication towards control centre applications requires standalone communication channels for each of devices (single TCP lint for each device). Also, up till now there was no standardized description for development of IEC gateways what significantly complicates development of adequate software support. Also, contrary to the station level SCADA systems, SCADA in control centres require lower subset of available process data what causes additional issues when configuring IEC devices for vertical communication with different hierarchy control levels. 2.2 Standardized architecture of software systems used for communication towards control centres The main idea described by IEC [7] standard is based on introducing middleware layer which is used for concentration of IEC process data. IEC data concentrator, also known as IEC proxy/gateway is simultaneously used as server and client for vertical IEC application-level services. In current IEC edition [8] server interface is on only enabled on devices while client interface is enabled on applications. By introducing middleware layer it is possible to additionally analyse and filter process data, as well as provide required data subset to the SCADA system without affecting process data semantics. The process of mapping IEC logical nodes from devices to the concentrator is illustrated in Figure 1. Namely, each of the logical nodes from devices is referenced by its image logical node available on the proxy/gateway application. According to the importance and reliability requirements of controlled systems, the IEC standard defines several possible configurations depending on a number of used client and server components. Figure 2 shows relationships of basic (a) and completely redundant (b) configuration of IEC concentrator. Figure 1 Logical node mapping [7]

3 MAKO CIGRE 2013 D2-054I 3/5 a) b) 2.3 Implementation requirements Figure 2 Configurations: a) basic, b) completely redundant [7] Implementing client and server interface for vertical communication in IEC systems is based on utilizing Manufacturing Message Specification (MMS) application-level protocol defined in ISO 9506 standard [9]. Developing IEC data concentrator requires implementation of both interfaces compliant to Abstract Communication Service Interface (ACSI) and middleware layer (proxy/server and proxy/client) requirements [1]. Middleware layer requires usage of additional state machine for device-to-application interactions adapted for control centre environment. Figure 3 shows an example of control model 1 (direct control with normal security) adapted at middleware layer. The Figure 2 shows interactions between communication endpoints which are brokered by middleware layer. Figure 3 ACSI interface example [7]

4 MAKO CIGRE 2013 D2-054I 4/5 2.4 Implementation requirements Figure 4 shows component-based architecture of PROZA NET SCADA system and outlines several communication protocols used on station level which are part of its integral functionalities. These protocols include IEC client interface based on self-developed software support without using and 3rd party MMS driver libraries. The latest upgrade od PROZA NET SCADA system includes IEC server interface, what together with the IEC client represents one of first prototypical implementations of IEC standard. By using IEC server interface, PROZA NET SCADA can be used as an IEC concentrator in case controlled devices are based on IEC protocol or can be used as protocol gateway in case controlled devices are communicating with any other telecontrol protocol (DNP3, IEC X). The mapping process has been aligned with current version of IEC standard draft and has been successfully applied in practice as a part of several commissioned remote monitoring systems. 3 CONCLUSION Figure 4 Component-based architecture of PROZA NET SCADA system This paper provide a brief overview of IEC standard which represents one of the most significant novelties which will be introduced in IEC second edition. This standard enables communication between field devices and control centres without losing process data semantics and provides standardized principles for developing IEC concentrators. Main functional guidelines required for developing software support required by IEC standard have been described. Also, PROZA NET SCADA system has been presented as one of the first prototypical implementations of IEC standard. Using IEC server interface in SCADA systems enables deployment of IEC data concentrators and gateways for other commonly used telecontrol protocols. 4 LITERATURE [1] Communication networks and systems for power utility automation - Part 7-2: Basic information and communication structure - Abstract communication service interface (ACSI), Int. Std. IEC ed2.0, Geneva, IEC, 2010 [2] Telecontrol equipment and systems - Part 5-101: Transmission protocols - Companion standard for basic telecontrol tasks, IEC Std , ed2.0, Geneva, IEC, 2003 [3] Telecontrol equipment and systems - Part 5-104: Transmission protocols - Network access for IEC using standard transport profiles, Int. Std. IEC ed2.0, Geneva, IEC, 2006 [4] DNP3 Specification - ALL PARTS, DNP User s Group;

5 MAKO CIGRE 2013 D2-054I 5/5 [5] Communication networks and systems for power utility automation - Part 80-1: Guideline to exchanging information from a CDC-based data model using IEC or IEC , Int.Std , ed1.0, Geneva, IEC, 2008 [6] Communication networks and systems in substations Part 7-1: Basic communication structure for substation and feeder equipment Principles and models, Int. Std. IEC ed1.0, Geneva, IEC, 2003 [7] Communication networks and systems for power utility automation - Part 90-2: Using IEC for the communication between control centers, DRAFT, Geneva, IEC, 2012 [8] Communication Networks and Systems in Substations - ALL PARTS, Int. Std. IEC SER ed1.0, Geneva, IEC, 2011 [9] ISO 9506 (all parts), Industrial automation systems Manufacturing Message Specification, Geneva, ISO, 2003