Jean-Charles Tournier

Applications of IEC 61850 in distribution automation

Distribution Automation (DA) is viewed as an integral component of the Smart Grid paradigm. It facilitates the employment of computer technology and communication infrastructure to advance management and operation of the distribution network from a semi-automated approach towards a fully automated one. SCADA systems, advanced sensors, and electronic controllers are integrated into the DA system in order to achieve the desired performance and reliability at the distribution network. Interoperability of all the components participating in the DA system requires communication standards covering not only the devices in the substation, but all the components from the substation to the point of interface with the end consumers. While the IEC 61850 standard was originally addressing applications and communications within the substation, recent work is undergone for extending it beyond the substation fence. With its object oriented structure, IEC 61850 can provide comprehensive and accurate information models for various components of distribution automation systems, while providing an efficient solution for this naturally multi-vendor environment. This paper provides some concrete examples on how IEC 61850 can be employed in the context of distribution automation applications, and what measures need to be taken to enable it to efficiently respond to some of the emerging technologies in DA systems.

Qinna, a component-based qos architecture

Component-Based Software Engineering is quickly becoming a mainstream approach to software development. At the same time, there is a massive shift from desktop applications to embedded communicating systems (e.g. PDAs or smartphones): it is especially the case for multimedia applications such as video players, music players, etc. Moreover, embedded communicating systems have to deal with open aspect: applications may come or leave the system on the fly. A key point of these systems is its ability to rigorously manage Quality of Service due to resource constraints. In this paper, we present a component-based QoS architecture well-suited for open systems, called Qinna. Qinna is defined using Fractal components and takes into consideration the main QoS concepts (specification, provision and management). An analysis and an experiment illustrate answers brought by Qinna to open system issues.

Precise time synchronization on a high available redundant ring protocol

An electric substation [1] is a node in the power grid network. It serves the purpose of transmitting and distributing electric energy from power sources to consumers, such as households or industrial plants. An electric substation is made of primary equipment (switchgears, breakers, transformers) and secondary equipment (sensors, merging units, intelligent electronic devices). The secondary equipment aims at protecting and controlling the primary one by sensing and analyzing various data.

Improving reliability of IEEE1588 in electric substation automation

The IEEE 1588 precision time protocol seems to be a promising way to handle synchronization requirements of tomorrow substation automation. However, one of the remaining issues is its lack of reliability in case of the loss of the GPS signal (e.g. due to atmospheric disturbances or failure of the GPS antenna) which would lead to the desynchronization of the devices inside a substation or between different substations. To keep the devices synchronized without the GPS signal, this paper explores different drift clock prediction techniques. Three main approaches based on statistical, probabilistic and time series techniques are evaluated. On one hand, a statistical-based prediction technique can easily reach an accuracy of less than 10 musec for a prediction duration of a couple of seconds at a minimal computing cost. On the other hand, a time series-based prediction technique can provide an accuracy of 76 musec over a period of 48 hours but at a much higher computing power cost. Finally, we identify the most suitable technique for different type of GPS signal loss that typically occurs in the context of substation automation.

On limitations of traditional multi-core and potential of many-core processing architectures for sparse linear solvers used in large-scale power system applications

As the power grid networks become larger and smarter, their operation and control become even more challenging due to the size of the underlying mathematical problems that need to be solved in real-time. In this paper, we report our experience on utilizing the main stream computation architecture to improve performance of solving a system of linear equations, the key part of most power system applications, using iterative methods. Since Conjugate Gradient (CG) algorithms have been applied to power system applications in the literature with a suggested benefit from parallelization, they are selected and evaluated against the mainstream computation architectures (i.e., multi-core CPU and many-core GPU) in the context of both power system state estimation and power flow applications. The evaluation results show that solving a system of linear equations using iterative methods is highly memory bonded and multi-core CPU and GPU computation architecture have different impacts on the performance of such an iterative solver: unlike multicore CPU, GPU can greatly improve the performance of CG-based iterative solver when matrices are well conditioned as typically encountered in the DC power flow formulation.

Applying Model Checking to Industrial-Sized PLC Programs

Programmable logic controllers (PLCs) are embedded computers widely used in industrial control systems. Ensuring that a PLC software complies with its specification is a challenging task. Formal verification has become a recommended practice to ensure the correctness of safety-critical software, but is still underused in industry due to the complexity of building and managing formal models of real applications. In this paper, we propose a general methodology to perform automated model checking of complex properties expressed in temporal logics [e.g., computation tree logic (CTL) and linear temporal logic (LTL)] on PLC programs. This methodology is based on an intermediate model (IM) meant to transform PLC programs written in various standard languages [structured text (ST), sequential function chart (SFC), etc.] to different modeling languages of verification tools. We present the syntax and semantics of the IM, and the transformation rules of the ST and SFC languages to the nuXmv model checker passing through the IM. Finally, two real cases studies of the European Organization for Nuclear Research (CERN) PLC programs, written mainly in the ST language, are presented to illustrate and validate the proposed approach.

Strategies to secure the IEEE 1588 protocol in digital substation automation

The IEEE 1588 Precision Time Protocol seems to be a promising way to handle the synchronization requirements of tomorrows substation automation based on IEC 61850. While a specific working group is tackling the security aspects of the protocols defined by IEC 61850, a secure IEEE 1588 protocol remains mostly uncovered in the specific context of substation automation. In this paper, we are focusing on securing IEEE 1588 for substation automation. We are analyzing and classifying the different attacks relevant for a substation and proposing a way to handle the logical disconnection of the time server and its clients that appears whenever an attack occurs. The method based on clock drift correction allows to keep a node synchronized for different period of time depending on the correction mechanism used. The implementation and experiments of the different drift correction mechanisms shows the tradeoff between the accuracy of the correction and the required computational time. By analyzing the different experiments, we can then match the computational power of a class of devices present in a substation and a correction technique.

A quantitative evaluation of IEC61850 process bus architectures

The IEC 61850 standard plays an important role in the smart grid landscape by providing an unified way of accessing and exchanging data related to substations equipment. While large parts of the standard are widely adopted and integrated by the different vendors, the 9–2 part, or process bus, remains a challenge because of the number of opposite constraints that have to be addressed at the same time, such as scalability, reliability, real-time and cost efficiency. This paper does not provide the way to implement the process bus, but rather gives means to evaluate and compare different process bus solutions. In this study, we are performing a quantitative evaluation of different process bus architectures along the reliability, availability, performance and cost criteria. The performance criteria encompasses the evaluation with respect to the real time constraints as well as the overall load of the communication infrastructure. The cost criteria identifies the initial investment cost for a given solution and also evaluates the maintenance cost over the life time of the process bus. The main contributions of this paper are (a) to give a full evaluation by integrating all relevant criteria; (b) explicitly explain how the different evaluations are performed; (c) to integrate all elements for the reliability calculation, especially the optical fibres which are usually omitted but considered as the least reliable elements; (d) to evaluate the latest redundancy protocols for automation networks such as PRP and HSR; and (e) to evaluate architectures that take full advantage of IEC 61850 by deploying protection and control functions in innovative ways.

Towards a framework for dedicated operating systems development in high-end computing systems

In the context of high-end computing systems, general-purpose operating systems impose overhead on the applications they support due to unneeded services. Although dedicated operating systems overcome this issue, they are difficult to develop or adapt. In this paper, we propose a framework, based on the component programming paradigm, which supports the development and adaptation of such operating systems. This framework makes possible the a la carte construction of operating systems which provide specific high-end computing system characteristics.

Bringing Automated Model Checking to PLC Program Development { A CERN Case Study {

Abstract Verification of critical software is a high priority but a challenging task for industrial control systems. Model checking appears to be an appropriate approach for this purpose. However, this technique is not widely used in industry yet, due to some obstacles. The main obstacles encountered when trying to apply formal verification techniques at industrial installations are the difficulty of creating models out of PLC programs and defining formally the specification requirements. In addition, models produced out of real-life programs have a huge state space, thus preventing the verification due to performance issues. Our work at CERN (European Organization for Nuclear Research) focuses on developing efficient automatic verification methods for industrial critical installations based on PLC (Programmable Logic Controller) control systems. In this paper, we present a tool generating automatically formal models out of PLC code. The tool implements a general methodology which can support several input languages, like the PLC programming languages defined in the IEC 61131 standard, as well as the model formalisms of different model checker tools. The tool supports the three main stages of model checking: system modelization, requirement formalization and counterexample analysis. In addition, a verification case study of a PLC program, written in Structured Text (ST) language implemented at CERN is described. The paper shows that the verification process is automatized and supported by the proposed tool, thus its difficulty is completely hidden for the control engineer.