The White Rabbit Time Synchronization Protocol for Synchrophasor Networks

Within the context of time dissemination techniques for power systems applications, the paper discusses the use of the White Rabbit (WR) protocol for synchrophasor networks. Specifically, the paper presents a Phasor Measurement Unit (PMU) integrating the WR technology and its experimental validation with a focus on the synchrophasor phase estimation in steady state conditions, by using a PMU calibrator generating the reference signals. We further compare the accuracy of the developed PMU with other state-of-the-art time synchronization technologies for PMUs. i.e., Global Positioning System (GPS) and Precision Time Protocol (PTP), demonstrating applicability of WR for PMU sensing networks

Impact of Time Dissemination Technologies on Synchrophasor Estimation Accuracy

The paper discusses the influence of the time synchronization technique on the synchrophasor estimation accuracy in modern Phasor Measurement Units (PMU). Specifically, we make reference to Global Positioning System (GPS), Precision Time Protocol (PTP) and White Rabbit time disseminations. The paper presents a PMU integrating the three technologies, and assess its performance in steady state conditions. The experimental validation demonstrates that the more deterministic the time source, the better the performance in terms of phase estimation accuracy

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

10 Gigabit White Rabbit: sub-nanosecond timing and data distribution

Time synchronization is a critical feature for many scientific facilities and industrial infrastructures. The required performance is progressively increasing everyday, for instance, few tens of nanoseconds for Fifth Generation (5G) networks or sub-nanosecond accuracy on next family of particle accelerators and astrophysics telescopes. Due to this exigent accuracy, many applications require specific timing dedicated networks, increasing the system cost and complexity. Under this context, the new IEEE 1588-2019 High Accuracy (HA) default profile is intensively based on White Rabbit (WR) which can provide sub-nanosecond accurate synchronization for Ethernet networks. However, current WR solutions have not been designed to work properly with high data bandwidth delivery services even in 1 Gigabit Ethernet (GbE) links. On this contribution, the authors propose a new architecture design that enables WR and, consequently, the IEEE 1588-2019 HA profile to be deployed over 10 GbE links solving the already identified data bandwidth problem. Furthermore, this work addresses different experiments needed to characterize the system performance in terms of time synchronization and data transfer. As final result, this contribution presents for the first time in the literature a new WR system which allows high bandwidth data exchange in 10 GbE networks while providing sub-nanosecond accuracy synchronization. The proposed solution maintains the time synchronization performance of existing WR 1 GbE devices with significant advantages in terms of latency and data bandwidth, enabling its deployment in applications that integrate data and synchronization information in the same network.European Union (EU) 725490H2020 ASTERICS 653477AMIGA7 RTI2018-096228-B-C3

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

Precision packet-based frequency transfer based on oversampling

Frequency synchronization of a distributed measurement system requires the transfer of an accurate frequency reference to all nodes. The use of a general-purpose packet-based network for this aim is analyzed in this paper, where oversampling is considered as a means to counter the effects of packet delay variation on time accuracy. A comprehensive analysis that includes the stability of the local clock is presented and shows that frequency transfer through a packet network of this kind is feasible, with an accuracy level that can be of interest to a number of distributed measurement applications

IEEE 1588 High Accuracy Default Profile: Applications and Challenges

Highly accurate synchronization has become a major requirement because of the rise of distributed applications, regulatory requests and position, navigation and timing backup needs. This fact has led to the development of new technologies which fulfill the new requirements in terms of accuracy and dependability. Nevertheless, some of these novel proposals have lacked determinism, robustness, interoperability, deployability, scalability or management tools preventing them to be extensively used in real industrial scenarios. Different segments require accurate timing information over a large number of nodes. Due to the high availability and low price of global satellite-based time references, many critical distributed facilities depend on them. However, the vulnerability to jamming or spoofing represents a well-known threat and back-up systems need to be deployed to mitigate it. The recently approved draft standard IEEE 1588-2019 includes the High Accuracy Default Precision Time Protocol Profile which is intensively based on the White Rabbit protocol. White Rabbit is an extension of current IEEE 1588-2008 network synchronization protocol for sub-nanosecond synchronization. This approach has been validated and intensively used during the last years. This paper revises the pre-standard protocol to expose the challenges that the High Accuracy profile will find after its release and covers existing applications, promising deployments and the technological roadmap, providing hints and an overview of features to be studied. The authors review different issues that have prevented the industrial adoption of White Rabbit in the past and introduce the latest developments that will facilitate the next IEEE 1588 High Accuracy extensive adoption.This work was supported in part by the AMIGA6 under Grant AYA2015-65973-C3-2-R, in part by the AMIGA7 under Grant RTI2018-096228-B-C32, and in part by the Torres Quevedo under Grant PTQ2018-010198

DFT-based Synchrophasor Estimation Algorithms and their Integration in Advanced Phasor Measurement Units for the Real-time Monitoring of Active Distribution Networks

The increasing penetration of Distributed Energy Resources (DERs) at the low and medium-voltage levels is determining major changes in the operational procedures of distribution networks (DNs) that are evolving from passive to active power grids. Such evolution is causing non-negligible problems to DN operators (DNOs) and calls for advanced monitoring infrastructures composed by distributed sensing devices capable of monitoring voltage and current variations in real-time. In this respect, Phasor Measurement Units (PMUs) definitely represent one of the most promising technologies. Their higher accuracy and reporting rates compared to standard monitoring devices, together with the possibility of reporting time-tagged measurements of voltage and current phasors, enable the possibility to obtain frequent and accurate snapshots of the status of the monitored grid. Nevertheless, the applicability of such technology to DNs has not been demonstrated yet since PMUs where originally conceived for transmission network applications. Within this context, this thesis first discusses and derives the requirements for PMUs expected to operate at power distribution level. This study is carried out by analyzing typical operating conditions of Active Distribution Networks (ADNs). Then, based on these considerations, an advanced synchrophasor estimation algorithm capable of matching the accuracy requirements of ADNs is formulated. The algorithm, called iterative-interpolated DFT (i-IpDFT) improves the performances of the Interpolated-DFT (IpDFT) method by iteratively compensating the effects of the spectral interference produced by the negative image of the spectrum and at the same time allows to reduce the window length up to two periods of a signal at the nominal frequency of the power system. In order to demonstrate the low computational complexity of such an approach, the developed algorithm has been subsequently optimized to be deployed into a dedicated FPGA-based PMU prototype. The influence of the PMU hardware components and particularly the effects of the stability and reliability of the adopted UTC-time synchronization technology have been verified. The PMU prototype has been metrologically characterized with respect to the previously defined operating conditions of ADNs using a dedicated PMU calibrator developed in collaboration with the Swiss Federal Institute of Metrology (METAS). The experimental validation has verified the PMU compliance with the class-P requirements defined in the IEEE Std. C37.118 and with most of the accuracy requirements defined for class-M PMUs with the exception of out of band interference tests

Cyber-attack on Packet-Based Time Synchronization Protocols: the Undetectable Delay Box

We present a cyber-attack on packet-based time synchronization protocols (PBTSP) with high-accuracy requirements. The cyber-attack is undetectable from the PBTSP's perspective and exploits a vulnerability that is in the nature of all PBTSPs. It can be successfully performed regardless of the cryptographic protocol that the PBTSP is protected with and it is undetectable by the clock-servo algorithm inside the target slave clock. To perform this cyber-attack, we built a "Delay Box" capable of advancing or delaying a slave clock by introducing a malicious offset of a few microseconds. We run experimental tests to the delay box to prove the magnitude of the attack and to confirm undetectability. We discuss possible countermeasures for this type of attack

A hybrid optical-wireless network for decimetre-level terrestrial positioning

Global navigation satellite systems (GNSS) are widely used for navigation and time distribution, features indispensable for critical infrastructure such as mobile communication networks, as well as emerging technologies like automated driving and sustainable energy grids. While GNSS can provide centimetre-level precision, GNSS receivers are prone to many-metre errors due to multipath propagation and obstructed view of the sky, which occur especially in urban areas where accurate positioning is needed most. Moreover, the vulnerabilities of GNSS, combined with the lack of a back-up system, pose a severe risk to GNSS-dependent technologies. Here, we demonstrate a terrestrial positioning system which is independent of GNSS and offers superior performance through a constellation of radio transmitters, connected and time-synchronised at the sub-nanosecond level through a fibre-optic Ethernet network. Employing optical and wireless transmission schemes similar to those encountered in mobile communication networks, and exploiting spectrally efficient virtual wideband signals, the detrimental effects of multipath propagation are mitigated, thus enabling robust decimetre-level positioning and sub-nanosecond timing in a multipath-prone outdoor environment. This work provides a glimpse of a future in which telecommunication networks provide not only connectivity, but also GNSS-independent timing and positioning services with unprecedented accuracy and reliability.Comment: 38 pages, 9 figures, 3 table