A Survey on Communication Networks for Electric System Automation

Published in Computer Networks 50 (2006) 877–897, an Elsevier journal. The definitive version of this publication is available from Science Direct. Digital Object Identifier:10.1016/j.comnet.2006.01.005In today’s competitive electric utility marketplace, reliable and real-time information become the key factor for reliable delivery of power to the end-users, profitability of the electric utility and customer satisfaction. The operational and commercial demands of electric utilities require a high-performance data communication network that supports both existing functionalities and future operational requirements. In this respect, since such a communication network constitutes the core of the electric system automation applications, the design of a cost-effective and reliable network architecture is crucial. In this paper, the opportunities and challenges of a hybrid network architecture are discussed for electric system automation. More specifically, Internet based Virtual Private Networks, power line communications, satellite communications and wireless communications (wireless sensor networks, WiMAX and wireless mesh networks) are described in detail. The motivation of this paper is to provide a better understanding of the hybrid network architecture that can provide heterogeneous electric system automation application requirements. In this regard, our aim is to present a structured framework for electric utilities who plan to utilize new communication technologies for automation and hence, to make the decision making process more effective and direct.This work was supported by NEETRAC under Project #04-157

MACsec Layer 2 Security in HSR Rings in Substation Automation Systems

The smart-grid concept takes the communications from the enclosed and protected environment of a substation to the wider city or nationwide area. In this environment, cyber security takes a key role in order to secure the communications. The challenge is to be able to secure the grid without impacting the latency while, at the same time, maintaining compatibility with older devices and non secure services. At the lower level, added security must not interfere with the redundancy and the latency required for the real-time substation automation communications. This paper studies how to integrate IEEE MAC Security standard (MACsec) in the substation environment, especially when used in substation system communications that have stringent response time requirements and zero recovery time as defined in IEC 62439-3.This work has been supported by the Ministerio de Economia y Competitividad of Spain within the project TEC2014-53785-R, and it has been carried out inside the Research and Education Unit UFI11/16 of the UPV/EHU and partially supported by the Basque Government within the funds for research groups of the Basque University system IT978-16 and within the project TFactory ER-2014/0016. In addition, FEDER funds and UPV/EHU Ph.D. scholarship funding are acknowledged

Study and Design of Inter-Range Instrumentation Group Time Code B Synchronization of IEC 61850 Sampled Values

Distribution substations are an important part of a chain which delivers energy from power production to customers. They transform the voltage level from transmission levels, usually 35kV and up, to distribution levels ranging between 600 and 35000 V. Recent developments in the instrument transformer field have been toward low-power solutions which use digital measurement values called sampled values in place of analog voltages and currents in substations. The IEC 61850-9-2 standard and its implementation guideline 9-2 LE by the UCA international users group define an interface for sampled values. This interface is used between an IED and LPIT. The main requirement of using sampled values is accurate time synchronization in order to prevent phase misalignment resulting in unnecessary protection function tripping. 9-2 LE defines two methods for synchronization: 1PPS and PTP. Today, PTP is widely used in the western markets, but due to costs associated with PTP-capable GPS clocks and Ethernet switches as well as vendor inoperability problems, some markets are hesitant to take into use. The purpose of this thesis is to propose a solution to this problem: use IRIG-B as a synchronization method in a PTP grandmaster. This paper discusses the differences between these two time synchronization topologies, associated costs, disturbance handling, accuracy and it also discusses the design of IRIG-B to PTP conversion done in a bay-level device. The device acts as a PTP grandmaster but the source comes from an IRIG-B clock instead of a GPS PTP grandmaster clock. The results shown in this thesis demonstrate that using IRIG-B as a main or redundant source in synchronization of sampled values is a more cost-effective option, especially if the station is to be retrofitted with sampled values configuration. The proposed bay level device also maintains the desired accuracy levels of ±1 µs set by IEC 61850-5.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Application of Advanced Early Warning Systems with Adaptive Protection

This project developed and field-tested two methods of Adaptive Protection systems utilizing synchrophasor data. One method detects conditions of system stress that can lead to unintended relay operation, and initiates a supervisory signal to modify relay response in real time to avoid false trips. The second method detects the possibility of false trips of impedance relays as stable system swings “encroach” on the relays’ impedance zones, and produces an early warning so that relay engineers can re-evaluate relay settings. In addition, real-time synchrophasor data produced by this project was used to develop advanced visualization techniques for display of synchrophasor data to utility operators and engineers

Investigating Performance and Reliability of Process Bus Networks for Digital Protective Relaying

To reduce the cost of complex and long copper wiring, as well as to achieve flexibility in signal communications, IEC 61850 part 9-2 proposes a process bus communication network between process level switchyard equipments, and bay level protection and control (P&C) Intelligent Electronic Devices (IEDs). After successful implementation of Ethernet networks for IEC 61850 standard part 8-1 (station bus) at several substations worldwide, major manufacturers are currently working on the development of interoperable products for the IEC 61850-9-2 based process bus. The major technical challenges for applying Ethernet networks at process level include: 1) the performance of time critical messages for protection applications; 2) impacts of process bus Ethernet networks on the reliability of substation protection systems. This work starts with the performance analysis in terms of time critical Sampled Value (SV) messages loss and/or delay over the IEC 61850-9-2 process bus networks of a typical substation. Unlike GOOSE, the SV message is not repeated several times, and therefore, there is no assurance that each SV message will be received from the process bus network at protection IEDs. Therefore, the detailed modeling of IEC 61850 based substation protection devices, communication protocols, and packet format is carried out using an industry-trusted simulation tool OPNET, to study and quantify number of SV loss and delay over the process bus. The impact of SV loss/delay on digital substation protection systems is evident, and recognized by several manufacturers. Therefore, a sample value estimation algorithm is developed in order to enhance the performance of digital substation protection functions by estimating the lost and delayed sampled values. The error of estimation is evaluated in detail considering several scenarios of power system relaying. The work is further carried out to investigate the possible impact of SV loss/delay on protection functions, and test the proposed SV estimation algorithm using the hardware setup. Therefore, a state-of-the-art process bus laboratory with the protection IEDs and merging unit playback simulator using industrial computers on the QNX hard-real-time platform, is developed for a typical IEC 61850-9-2 based process bus network. Moreover, the proposed SV estimation algorithm is implemented as a part of bus differential and transmission line distance protection IEDs, and it is tested using the developed experimental setup for various SV loss/delay scenarios and power system fault conditions. In addition to the performance analysis, this work also focuses on the reliability aspects of protection systems with process bus communication network. To study the impact of process bus communication on reliability indices of a substation protection function, the detailed reliability modeling and analysis is carried out for a typical substation layout. First of all, reliability analysis is done using Reliability Block Diagrams (RBD) considering various practical process bus architectures, as well as, time synchronization techniques. After obtaining important failure rates from the RBD, an extended Markov model is proposed to analyze the reliability indices of protection systems, such as, protection unavailability, abnormal unavailability, and loss of security. It is shown with the proposed Markov model that the implementation of sampled value estimation improves the reliability indices of a protection system

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

A survey on cyber security for smart grid communications

A smart grid is a new form of electricity network with high fidelity power-flow control, self-healing, and energy reliability and energy security using digital communications and control technology. To upgrade an existing power grid into a smart grid, it requires significant dependence on intelligent and secure communication infrastructures. It requires security frameworks for distributed communications, pervasive computing and sensing technologies in smart grid. However, as many of the communication technologies currently recommended to use by a smart grid is vulnerable in cyber security, it could lead to unreliable system operations, causing unnecessary expenditure, even consequential disaster to both utilities and consumers. In this paper, we summarize the cyber security requirements and the possible vulnerabilities in smart grid communications and survey the current solutions on cyber security for smart grid communications. © 2012 IEEE

Tarkan ja luotettavan ajan siirto kantaverkossa

This master’s thesis is about time distribution that supports substation applications needed for power transmission. The work was done for the Telecommunication department of Finland’s power transmission system operator Fingrid Oyj. This thesis answers to the following question: What is the need for accurate and synchronized time in power substations and how it will be delivered? Fingrid’s telecommunication network supports the power transmission grid and its operation. Telecommunication network can distribute time to power substations for the applications that need synchronized and accurate time. Current telecommunication equipment used in Fingrid is getting old and new techniques are planned to be implemented. When Fingrid is acquiring new communication equipment, they need to set requirements on the capability to distribute time. This thesis is an initial effort to investigate time distribution requirements for Fingrid’s needs. This thesis aids Fingrid Telecommunication department to define requirements for time distribution. For this thesis, I met with multiple Fingrid professionals, telecommunication device suppliers and time distribution researchers. This thesis answers to its research questions by means of a literature review and interviews.Tämä diplomityö käsittelee ajansiirron vaikutusta sähköasemasovellusten toimintaan. Työ tehtiin Suomen kantaverkkoyhtiö Fingrid Oyj:n tietoliikenneyksikölle. Fingridin tietoliikenneverkko on osa kantaverkkoa ja mahdollistaa sähköjärjestelmän toiminteita. Tietoliikenneverkon yksi palvelu on synkronoidun ajan siirtäminen sähköasemille. Nykyinen tietoliikennetekniikka on vanhenemassa ja uutta laitteistoa suunnitellaan hankittavaksi ja testattavaksi. Tämän diplomityön tarkoitus on selvittää mikä on järkevä tapa toteuttaa ajan siirto ja kuinka tarkkaa sen pitää olla. Työ auttaa tietoliikenneyksikköä hankinnan vaatimusmäärittelyssä ajansiirron osalta. Työtä varten on tavattu monia Fingridin asiantuntijoita, tietoliikennelaitetoimittajia sekä ajansiirron asiantuntijoita. Työ vastaa tutkimuskysymykseen kirjallisuuskatsauksen ja haastattelujen perusteella