74 research outputs found
Software Defined Networks based Smart Grid Communication: A Comprehensive Survey
The current power grid is no longer a feasible solution due to
ever-increasing user demand of electricity, old infrastructure, and reliability
issues and thus require transformation to a better grid a.k.a., smart grid
(SG). The key features that distinguish SG from the conventional electrical
power grid are its capability to perform two-way communication, demand side
management, and real time pricing. Despite all these advantages that SG will
bring, there are certain issues which are specific to SG communication system.
For instance, network management of current SG systems is complex, time
consuming, and done manually. Moreover, SG communication (SGC) system is built
on different vendor specific devices and protocols. Therefore, the current SG
systems are not protocol independent, thus leading to interoperability issue.
Software defined network (SDN) has been proposed to monitor and manage the
communication networks globally. This article serves as a comprehensive survey
on SDN-based SGC. In this article, we first discuss taxonomy of advantages of
SDNbased SGC.We then discuss SDN-based SGC architectures, along with case
studies. Our article provides an in-depth discussion on routing schemes for
SDN-based SGC. We also provide detailed survey of security and privacy schemes
applied to SDN-based SGC. We furthermore present challenges, open issues, and
future research directions related to SDN-based SGC.Comment: Accepte
On The Security of Wide Area Measurement System and Phasor Data Collection
Smart grid is a typical cyber-physical system that presents the dependence of power system operations on cyber infrastructure for control, monitoring, and protection purposes. The rapid deployment of phasor measurements in smart grid transmission system has opened opportunities to utilize new applications and enhance the grid operations. Thus, the smart grid has become more dependent on communication and information technologies such as Wide Area Measurement Systems (WAMS). WAMS are used to collect real-time measurements from different sensors such as Phasor Measurement Units (PMUs) installed across widely dispersed areas. Such system will improve real-time monitoring and control; however, recent studies have pointed out that the use of WAMS introduces significant vulnerabilities to cyber-attacks that can be leveraged by attackers. Therefore, preventing or reducing the damage of cyber attacks onWAMS is critical to the security of the smart grid. In this thesis, we focus our attention on the relation between WAMS security and the IP routing protocol, which is an essential aspect to the collection of sensors measurements.
Synchrophasor measurements from different PMUs are transferred through a data network and collected at one or multiple data concentrators. The timely collection of phasors from PMU dispersed across the grid allows to maintain system observability and take corrective actions when needed. This collection is made possible through Phasor Data Concentrators (PDCs) that time-align and aggregate phasor measurements, and forward the resulting stream to be used by monitoring and control applications. WAMS applications relying on these measurements have strict and stringent delay requirements, e.g., end-to-end delay as well as delay variation between measurements from different PMUs. Measurements arriving past a predetermined time period at a data concentrator will be dropped, causing incompleteness of data and affecting WAMS applications and hence the system’s operations. It has been shown that non-functional properties, such as data delay and packet drops, have a negative impact on the system functionality.
We show that simply forwarding measurements from PMUs through shortest routes to phasor data collectors may result in data being dropped at their destinations. We believe therefore that there is a strong interplay between the routing paths (delays along the paths) for gathering the measurements and the value of timeout period. This is particularly troubling when a malicious attacker deliberately causes delays on some communication links along the shortest routes. Therefore, we present a mathematical model for constructing forwarding trees for PMUs’ measurements which satisfy the end to end delay as well as the delay variation requirements of WAMS applications at data concentrators. We show that a simple shortest path routing will result in larger fraction of data drop and that our method will find a suitable solution. Then, we study the relation between cyber-attack propagation and IP multicast routing. To this extent, we formulate the problem as the construction of a multicast tree that minimizes the propagation of cyber-attacks while satisfying real-time and capacity requirements. The proposed attack propagation multicast tree is evaluated using different IEEE test systems. Finally, cyber-attacks resulting in the disconnection of PDC(s) from WAMS initiate a loss of its phasor stream and incompleteness in the observability of the power system. Recovery strategies based on the re-routing of lost phasors to other connected and available PDCs need to be designed while considering the functional requirements of WAMS. We formulate a recovery strategy from loss of compromised or failed PDC(s) in the WAMS network based on the rerouting of disconnected PMUs to functional PDCs. The proposed approach is mathematically formulated as a linear program and tested on standard IEEE test systems. These problems will be extensively studied throughout this thesis
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Novel performance evaluation of information and communication technologies to enable wide area monitoring systems for enhanced transmission network operation
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.The penetration of renewable energy sources has increased significantly in recent years due to the ongoing depletion of conventional resources and the transition to a low carbon energy system. Renewable energy sources such as wind energy are highly intermittent and unpredictable in nature, which makes the operation of the power grid more dynamic and therefore more complex. In order to operate the power system reliably under such conditions, Phasor Measurement Units (PMUs) through the use of satellite technology can offer a state-of-the-art Wide Area Monitoring System (WAMS) for improving power system monitoring, control and protection. They can improve the operation by providing highly precise and synchronised measurements near to real-time with higher frequency and accuracy. In order to achieve such objectives, a high-speed and reliable communications infrastructure is required to transfer time-critical PMU data from remote locations to the control centre. The signals measured by PMUs are transmitted across Local and Wide Area Networks, where they may encounter excessive delays. Signal delays can have a disruptive effect and make applications at best inefficient and at worse ineffective.
The main research contribution of this thesis is the performance evaluation of communication infrastructures for WAMS. The evaluation begins from inside substations and continues over wide areas from substations to control centre. Through laboratory-based investigations and simulations, the performance of communications infrastructure in a typical power system substation has been analysed. In addition, the performance evaluation of WAMS communications infrastructure has been presented. In the modelling and analysis, an existing WAMS as installed on the GB transmission system has been considered. The actual PMU packets as received at the Phasor Data Concentrator (PDC) were captured for latency analysis. A novel algorithmic procedure has been developed and implemented to automate the large-scale latency calculations. Furthermore, the internal delays of PMUs have been investigated, determined and analysed. Subsequently, the WAMS has been simulated and detailed comparisons have been performed between the simulated model results and WAMS performance data captured from the actual WAMS. The validated WAMS model has been used for analysing possible future developments as well as to test newly proposed mechanisms, protocols, etc. in order to improve the communications infrastructure performance
Evaluation of the IEC 61850 Communication Solutions
Initially, when the IEC 61850 standard was prepared, it was intended to be used within the limits of a substation for information exchange between devices. In the course of time and due to the standard’s advantages, its concepts are nowadays used as well in other application areas of the power utility system. The IEC 61850 is based to the maximum extent on other existing communication standards (IEC/IEEE/ISO/OSI), offering among others: visualization of the real applications through the ASCI interface, standardized messages to be exchanged (GOOSE, SV), one configuration language regardless of the device (IED) type/brand, and mapping to already implemented computing protocols (MMS, TCP/IP, Ethernet). The features mentioned above lead to cost reduction, reliability, and interoperability, making the IEC61850 the dominant standard for intra- and inter-substation communication.
The parts 90-1 and 90-5 of the IEC 61850 standard concern the application of the tunneling and routing method in order to extend the communication beyond the substation’s limits. Although they establish the theoretical background, it can be mentioned a lack of information regarding real applications. So, the objective of this thesis was at first to establish the communication link which will allow the communication of devices belonging to different LANs and second, the acquiring of the round trip times from the exchanged messages. The experiments were conducted by a combination of software (Hamachi) and embedded platform (BeagleBone) pinging to each other first via tunneling and next via 4G mobile network. The acquired round-trip times were used to evaluate and compare the tunneling and the 4G routing method, estimating in parallel what are the perspectives of these methods to be used for inter-substation communication.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format
An Information-Centric Communication Infrastructure for Real-Time State Estimation of Active Distribution Networks
© 2010-2012 IEEE.The evolution toward emerging active distribution networks (ADNs) can be realized via a real-time state estimation (RTSE) application facilitated by the use of phasor measurement units (PMUs). A critical challenge in deploying PMU-based RTSE applications at large scale is the lack of a scalable and flexible communication infrastructure for the timely (i.e., sub-second) delivery of the high volume of synchronized and continuous synchrophasor measurements. We address this challenge by introducing a communication platform called C-DAX based on the information-centric networking (ICN) concept. With a topic-based publish-subscribe engine that decouples data producers and consumers in time and space, C-DAX enables efficient synchrophasor measurement delivery, as well as flexible and scalable (re)configuration of PMU data communication for seamless full observability of power conditions in complex and dynamic scenarios. Based on the derived set of requirements for supporting PMU-based RTSE in ADNs, we design the ICN-based C-DAX communication platform, together with a joint optimized physical network resource provisioning strategy, in order to enable the agile PMU data communications in near real-time. In this paper, C-DAX is validated via a field trial implementation deployed over a sample feeder in a real-distribution network; it is also evaluated through simulation-based experiments using a large set of real medium voltage grid topologies currently operating live in The Netherlands. This is the first work that applies emerging communication paradigms, such as ICN, to smart grids while maintaining the required hard real-time data delivery as demonstrated through field trials at national scale. As such, it aims to become a blueprint for the application of ICN-based general purpose communication platforms to ADNs
Experimental Comparison of Multicast Authentication for Wide Area Monitoring Systems
Multicast is proposed as a preferred communication mechanism for many power grid applications. One of the biggest challenges for multicast in smart grid is ensuring source authentication without violating the stringent time requirement. The research community and standardization bodies have proposed several authentication mechanisms for smart grid multicast applications. In this paper, we evaluate different authentication schemes and identify the best candidates for phasor data communication in wide area monitoring systems (WAMS). We first do an extensive literature review of existing solutions and establish a short list of schemes to evaluate. Second we make an experimental comparison of the chosen schemes in an operational smart grid pilot and evaluate the performance of these schemes by using the following metrics: computation, communication and key management overheads. The best candidates we consider are two variants of ECDSA, TV-HORS and three variants of Incomplete-key-set. We find ECDSA without pre-computed tokens and all the Incomplete-key-set variants are inapplicable for WAMS due to their high computation overhead. The ECDSA variant that uses pre-computed tokens and TV-HORS perform well in all metrics; however, TV-HORS has potential drawbacks due to a large key management overhead as a result of the frequent distribution of a large public key per source
Redundancy in Communication Networks for Smart Grids
Traditional electric power grids are currently undergoing fundamental changes: Representative examples are the increase in the penetration of volatile and decentralized renewable-energy sources and the emerging distributed energy-storage systems. These changes are not viable without the introduction of automation in grid monitoring and control, which implies the application of information and communication technologies (ICT) in power systems. Consequently, there is a transition toward smart grids. IEEE defines smart grid as follows: "The integration of power, communications, and information technologies for an improved electric power infrastructure serving loads while providing for an ongoing evolution of end-use applications" . The indispensable components of the future smart grids are the communication networks. Many well-established techniques and best practices, applied in other domains, are revisited and applied in new ways. Nevertheless, some gaps still need to be bridged due to the specific requirements of the smart-grid communication networks. Concretely, a challenging objective is to fulfill reliability and low-delay requirements over the wide-area networks, commonly used in smart grids. The main ``playground" for the work presented in this thesis is the smart-grid pilot of the EPFL campus. It is deployed on the operational medium-voltage distribution network of the campus. At the time of the writing of this thesis, the real-time monitoring of this active distribution network has been already put in place, as the first step toward the introduction of control and protection. The monitoring infrastructure relies on a communication network that is a representative example of the smart-grid communication networks. Keeping all this in mind, in this thesis, the main topic that we focus on, is the assurance of data communication over redundant network-infrastructure in industrial environments. This thesis consists of two parts that correspond to the two aspects of the topic that we address. In the first part of the thesis, we evaluate existing, well-established, technologies and solutions in the context of the EPFL smart-grid pilot. We report on the architecture of the communication network that we built on our campus. In addition, we go into more detail by reporting on some of the characteristics of the devices used in the network. We also discuss security aspects of the MPLS Transport Profile (MPLS-TP) which is one of the proposed technologies in the context of smart grids. In the second part of this thesis, we propose new solutions. While designing our campus smart-grid network, we analyzed the imposed requirements and recognized the need for a solution for reliable packet delivery within stringent delay constraints over a redundant network-infrastructure. The existing solutions for exploiting network redundancy, such as the parallel redundancy protocol (PRP), are not viable for IP-layer wide-area networks, a key element of emerging smart grids. Other solutions (MPLS-TP for example) do not meet the stringent delay requirement. To address this issue, we present a transport-layer solution: the IP-layer parallel redundancy protocol (iPRP). In the rest of the thesis, we analyze the methods for implementing fail-independent paths that are fundamental for the optimal operation of iPRP, in SDN-based networks. We also evaluate the benefits of iPRP in wireless environments. We show that, with a help of iPRP, the performance of the communication based on the Wi-Fi technology can be significantly improved
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