David M. Laverty

Telecommunications for Smart Grid: Backhaul solutions for the distribution network

Telecommunications are an essential component of emerging Smart Grid technologies. Up until now, power system telecoms planning have largely focused on transmission with less investment in the distribution network. Presently there is a need for a universal system over which all messaging may be achieved. With the rise of protocols such as IEC 61850 there is growing momentum to start installing telecoms so as to exploit the benefits on offer, but the challenge is now how to correctly engineer a system that can accommodate rapid growth alongside demand for throughput and real-time performance. This paper reviews a number of last-mile access technologies and proposes a model telecoms network for Smart Grids.

Synchrophasor Broadcast Over Internet Protocol for Distributed Generator Synchronization

Synchronous islanded operation involves continuously holding an islanded power network in virtual synchronism with the main power system to aid paralleling and avoid potentially damaging out-of-synchronism reclosure. This requires phase control of the generators in the island and the transmission of a reference signal from a secure location on the main power system. Global positioning system (GPS) time-synchronized phasor measurements transmitted via an Internet protocol (IP) are used for the reference signal. However, while offering low cost and a readily available solution for distribution networks, IP communications have variable latency and are susceptible to packet loss, which can make time-critical control applications difficult. This paper investigates the ability of the phase-control system to tolerate communications latency. Phasor measurement conditioning algorithms that can tolerate latency are used in the phase-control loop of a 50-kVA diesel generator.

The OpenPMU Platform for Open-Source Phasor Measurements

OpenPMU is an open platform for the development of phasor measurement unit (PMU) technology. A need has been identified for an open-source alternative to commercial PMU devices tailored to the needs of the university researcher and for enabling the development of new synchrophasor instruments from this foundation. OpenPMU achieves this through open-source hardware design specifications and software source code, allowing duplicates of the OpenPMU to be fabricated under open-source licenses. This paper presents the OpenPMU device based on the Labview development environment. The device is performance tested according to the IEEE C37.118.1 standard. Compatibility with the IEEE C37.118.2 messaging format is achieved through middleware which is readily adaptable to other PMU projects or applications. Improvements have been made to the original design to increase its flexibility. A new modularized architecture for the OpenPMU is presented using an open messaging format which the authors propose is adopted as a platform for PMU research.

Techniques for Multiple-Set Synchronous Islanding Control

Power system islanding can improve the continuity of power supply. Synchronous islanded operation enables the islanded system to remain in phase with the main power system while not electrically connected, so avoiding out-of-synchronism re-closure. Specific consideration is required for the multiple-set scenario. In this paper a suitable island management system is proposed, with the emphasis being on maximum island flexibility by allowing passive islanding transitions to occur, facilitated by intelligent control. These transitions include: island detection, identification, fragmentation, merging and return-to-mains. It can be challenging to detect these transitions while maintaining synchronous islanded operation. The performance of this control system in the presence of a variable wind power in-feed is also examined. A Mathworks SimPowerSystems simulation is used to investigate the performance of the island management system. The benefit and requirements for energy storage, communications and distribution system protection for this application are considered.

Principal Component Analysis of Wide-Area Phasor Measurements for Islanding Detection—A Geometric View

This paper presents a new technique for the detection of islanding conditions in electrical power systems. This problem is especially prevalent in systems with significant penetrations of distributed renewable generation. The proposed technique is based on the application of principal component analysis (PCA) to data sets of wide-area frequency measurements, recorded by phasor measurement units. The PCA approach was able to detect islanding accurately and quickly when compared with conventional RoCoF techniques, as well as with the frequency difference and change-of-angle difference methods recently proposed in the literature. The reliability and accuracy of the proposed PCA approach is demonstrated by using a number of test cases, which consider islanding and nonislanding events. The test cases are based on real data, recorded from several phasor measurement units located in the U.K. power system.

Anti-islanding detection using Synchrophasors and Internet Protocol telecommunications

This paper presents a method of improving anti-islanding detection for distributed generation by application of a wide-area measurement system. Present anti-islanding solutions were developed when installed capacity of distributed generation was low. Issues such as nuisance tripping, cascade tripping and poor anti-islanding detection sensitivity common with present solutions could be justified since distributed generation did not represent a substantial in-feed to the national grid. Today, the installed capacity of distributed generation constitutes a significant proportion of system demand. Consequently the problems with present anti-islanding solutions require a solution. This paper will describe in detail how the proposed system achieves this in an intuitive and cost effective manner and has the potential to be a component of a Smart Grid. A wide area measurement system based on Phasor Measurement Unit (PMU) technology provides distributed generators with live, real-time, data from secure points on the national grid. This data is communicated via a robust, secure, Internet Protocol (IPv6) telecommunications network.

Internet based loss-of-mains detection for distributed generation

This paper discusses methods of using the Internet as a communications media between distributed generator sites to provide new forms of loss-of-mains protection. An analysis of the quality of the communications channels between several nodes on the network was carried out experimentally. It is shown that Internet connections in urban environments are already capable of providing real-time power system protection, whilst rural Internet connections are borderline suitable but could not yet be recommended as a primary method of protection. Two strategies of providing loss-of-mains across Internet protocol are considered, broadcast of a reference frequency or phasor representing the utility and an Internet based inter-tripping scheme.

Internet based phasor measurement system for phase control of synchronous islands

The contribution of embedded generation to the connected capacity of the power system is increasing. In order to make best use of this resource, splitting the distribution network, also known as islanding, is being considered by some utilities. Operating the island in synchronism with the main network is preferred as this prevents out of phase reconnection of the island. This paper examines the technical challenges involved with emphasis on wide area telecommunications delay and time synchronization. The development of a phasor measurement and phase control system is shown and an experimental demonstration of a phase difference controller presented.

STPA-SafeSec: Safety and security analysis for cyber-physical systems

Abstract Cyber-physical systems tightly integrate physical processes and information and communication technologies. As todays critical infrastructures, e.g., the power grid or water distribution networks, are complex cyber-physical systems, ensuring their safety and security becomes of paramount importance. Traditional safety analysis methods, such as HAZOP, are ill-suited to assess these systems. Furthermore, cybersecurity vulnerabilities are often not considered critical, because their effects on the physical processes are not fully understood. In this work, we present STPA-SafeSec, a novel analysis methodology for both safety and security. Its results show the dependencies between cybersecurity vulnerabilities and system safety. Using this information, the most effective mitigation strategies to ensure safety and security of the system can be readily identified. We apply STPA-SafeSec to a use case in the power grid domain, and highlight its benefits.

Synchrophasor-Based Islanding Detection for Distributed Generation Systems Using Systematic Principal Component Analysis Approaches

Systematic principal component analysis (PCA) methods are presented in this paper for reliable islanding detection for power systems with significant penetration of distributed generations (DGs), where synchrophasors, recorded by phasor measurement units, are used for system monitoring. Existing islanding detection methods, such as rate-of-change-of-frequency and vector shift are fast for processing local information; however, with the growth in installed capacity of DGs, they suffer from several drawbacks. Incumbent genset islanding detection cannot distinguish a system-wide disturbance from an islanding event, leading to maloperation. The problem is even more significant when the grid does not have sufficient inertia to limit frequency divergences in the system fault/stress due to the high penetration of DGs. To tackle such problems, this paper introduces PCA methods for islanding detection. A simple control chart is established for intuitive visualization of the transients. A recursive PCA scheme is proposed as a reliable extension of the PCA method to reduce the false alarms for time-varying process. To further reduce the computational burden, the approximate linear dependence condition errors are calculated to update the associated PCA model. The proposed PCA and RPCA methods are verified by detecting abnormal transients occurring in the U.K. utility network.