Peak-ratio analysis method for enhancement of LOM protection using M class PMUs

A novel technique for loss of mains (LOM) detection, using Phasor Measurement Unit (PMU) data, is described in this paper. The technique, known as the Peak Ratio Analysis Method (PRAM), improves both sensitivity and stability of LOM protection when compared to prevailing techniques. The technique is based on a Rate of Change of Frequency (ROCOF) measurement from M-class PMUs, but the key novelty of the method lies in the fact that it employs a new “peak-ratio” analysis of the measured ROCOF waveform during any frequency disturbance to determine whether the potentially-islanded element of the network is grid connected or not. The proposed technique is described and several examples of its operation are compared with three competing LOM protection methods that have all been widely used by industry and/or reported in the literature: standard ROCOF, Phase Offset Relay (POR) and Phase Angle Difference (PAD) methods. It is shown that the PRAM technique exhibits comparable performance to the others, and in many cases improves upon their abilities, in particular for systems where the inertia of the main power system is reduced, which may arise in future systems with increased penetrations of renewable generation and HVDC infeed

PMU-Based ROCOF Measurements: Uncertainty Limits and Metrological Significance in Power System Applications

In modern power systems, the Rate-of-Change-of-Frequency (ROCOF) may be largely employed in Wide Area Monitoring, Protection and Control (WAMPAC) applications. However, a standard approach towards ROCOF measurements is still missing. In this paper, we investigate the feasibility of Phasor Measurement Units (PMUs) deployment in ROCOF-based applications, with a specific focus on Under-Frequency Load-Shedding (UFLS). For this analysis, we select three state-of-the-art window-based synchrophasor estimation algorithms and compare different signal models, ROCOF estimation techniques and window lengths in datasets inspired by real-world acquisitions. In this sense, we are able to carry out a sensitivity analysis of the behavior of a PMU-based UFLS control scheme. Based on the proposed results, PMUs prove to be accurate ROCOF meters, as long as the harmonic and inter-harmonic distortion within the measurement pass-bandwidth is scarce. In the presence of transient events, the synchrophasor model looses its appropriateness as the signal energy spreads over the entire spectrum and cannot be approximated as a sequence of narrow-band components. Finally, we validate the actual feasibility of PMU-based UFLS in a real-time simulated scenario where we compare two different ROCOF estimation techniques with a frequency-based control scheme and we show their impact on the successful grid restoration.Comment: Manuscript IM-18-20133R. Accepted for publication on IEEE Transactions on Instrumentation and Measurement (acceptance date: 9 March 2019

Performance of loss-of-mains detection in multi-generator power islands

This paper presents an investigation of the impact of multi-generator power islands on the performance of the most-commonly used anti-islanding protection method, Rate of Change of Frequency (ROCOF). In particular, various generating technology mixes including Photovoltaic panels (PV), Doubly Fed Induction Generators (DFIGs) and Synchronous Generators (SG) are considered. The Non-Detection Zone (NDZ) for a range of ROCOF setting options is assessed systematically and expressed as a percentage of generator MVA rating. It was discovered that ROCOF protection becomes very ineffective when protection time delay is applied. In the majority of islanding situations the generator is disconnected by frequency-based G59 protection

Improving Grid Hosting Capacity and Inertia Response with High Penetration of Renewable Generation

To achieve a more sustainable supply of electricity, utilizing renewable energy resources is a promising solution. However, the inclusion of intermittent renewable energy resources in electric power systems, if not appropriately managed and controlled, will raise a new set of technical challenges in both voltage and frequency control and jeopardizes the reliability and stability of the power system, as one of the most critical infrastructures in the today’s world. This dissertation aims to answer how to achieve high penetration of renewable generations in the entire power system without jeopardizing its security and reliability. First, we tackle the data insufficiency in testing new methods and concepts in renewable generation integration and develop a toolkit to generate any number of synthetic power grids feathering the same properties of real power grids. Next, we focus on small-scale PV systems as the most growing renewable generation in distribution networks and develop a detailed impact assessment framework to examine its impacts on the system and provide installation scheme recommendations to improve the hosting capacity of PV systems in the distribution networks. Following, we examine smart homes with rooftop PV systems and propose a new demand side management algorithm to make the best use of distributed renewable energy. Finally, the findings in the aforementioned three parts have been incorporated to solve the challenge of inertia response and hosting capacity of renewables in transmission network

Peak-ratio analysis method for enhancement of LOM protection using M class PMUs

Loss of Mains (LOM) occurs when part of the utility network containing distributed generation (DG) is disconnected from the remainder of the system. Detecting LOM will become more important in the future as higher amounts of DG will be connected to increase the use of renewable energy sources, to reduce emissions and to reduce power transmission losses. In some cases, DG can be capable of supplying loads within an island and the islanded system can remain stable.;However, safety issues arise if LOM persists and, accordingly, islanded operation is not permitted in the majority of utility systems throughout the world. Wide area monitoring systems, using synchronised phasor measurements, which are beginning to play an increasing role in monitoring and control in transmission networks, may offer opportunities to improve the performance of LOM protection in distribution networks, but may require some form of communications.;A novel technique for LOM detection, using Phasor Measurement Unit (PMU) data, is described in this thesis. The technique, known as the Peak Ratio Analysis Method (PRAM), is shown to improve both the sensitivity and stability of LOM protection when compared to prevailing techniques.;The technique is based on a Rate of Change of Frequency (ROCOF) measurement from M-class PMUs, but the key novelty of the method lies in the fact that it employs a new 'peak-ratio' analysis of the measured ROCOF waveform during any frequency disturbance to determine whether the potentially-islanded element of the network remains connected to the main system or not (i.e. it detects when islanding, or loss of mains, has occurred).;The proposed technique is described and several examples of its operation are compared with three competing LOM protection methods that have all been widely used by industry and/or reported in the literature: standard ROCOF, Phase Offset Relay (POR) and Phase Angle Difference (PAD) methods. It is shown that the PRAM technique exhibits comparable performance to the others, and in many cases improves upon their abilities; in particular for systems where the inertia of the main power system is reduced, which may be the case in future systems with increased penetrations of renewable generation and HVDC infeeds.Loss of Mains (LOM) occurs when part of the utility network containing distributed generation (DG) is disconnected from the remainder of the system. Detecting LOM will become more important in the future as higher amounts of DG will be connected to increase the use of renewable energy sources, to reduce emissions and to reduce power transmission losses. In some cases, DG can be capable of supplying loads within an island and the islanded system can remain stable.;However, safety issues arise if LOM persists and, accordingly, islanded operation is not permitted in the majority of utility systems throughout the world. Wide area monitoring systems, using synchronised phasor measurements, which are beginning to play an increasing role in monitoring and control in transmission networks, may offer opportunities to improve the performance of LOM protection in distribution networks, but may require some form of communications.;A novel technique for LOM detection, using Phasor Measurement Unit (PMU) data, is described in this thesis. The technique, known as the Peak Ratio Analysis Method (PRAM), is shown to improve both the sensitivity and stability of LOM protection when compared to prevailing techniques.;The technique is based on a Rate of Change of Frequency (ROCOF) measurement from M-class PMUs, but the key novelty of the method lies in the fact that it employs a new 'peak-ratio' analysis of the measured ROCOF waveform during any frequency disturbance to determine whether the potentially-islanded element of the network remains connected to the main system or not (i.e. it detects when islanding, or loss of mains, has occurred).;The proposed technique is described and several examples of its operation are compared with three competing LOM protection methods that have all been widely used by industry and/or reported in the literature: standard ROCOF, Phase Offset Relay (POR) and Phase Angle Difference (PAD) methods. It is shown that the PRAM technique exhibits comparable performance to the others, and in many cases improves upon their abilities; in particular for systems where the inertia of the main power system is reduced, which may be the case in future systems with increased penetrations of renewable generation and HVDC infeeds

Analysis of necessary evolution of the regulatory framework to enable the Web-of-Cells development : [ELECTRA]

Deliverable D3.3 discusses how the solutions proposed within ELECTRA can be tailored to the typical rules that will be imposed by national/EU regulators, and/or how the regulations can be extended or adapted to cover the new concepts developed in ELECTRA (Web-of-Cells architecture, associated control mechanisms, Cell System Operator role, etc.)

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen

The development of relations between Russia and the European Union

Russians overwhelmingly see themselves as part of Europe, yet appreciate their Asian connection; there is a continuation of the 'Great Debate' between Westernizers and Slavophiles. Decades of official acrimony towards the EC were followed by acceptance of West European integration, if it did not involve Russia's isolation. After a period of rapprochement with Europe, a feeling of betrayal has recently grown in Russia. Nevertheless, the trend is for ever closer links with the West. From the EU's perspective, Member States' conflicting views on the New Europe hinder a united approach to solutions. The EU has gained a very strong position with the collapse of the CMEA. The EU-Russia Partnership Agreement shows that vested interests of EU producers often prevail, yet useful structures for political dialogue were nonetheless created, and the prospect of a common free trade area is momentous. The need for a new security structure is unlikely to be satisfied by NATO's Partnership for Peace, but the EU has failed to lead European calls for a WEU or CSCE-based security framework. The inheritance of the command economy has damaged foreign trade and investment conditions. Despite the transformation of the economy, much needs to be done to improve investment conditions for foreigners as well as for potential exporters - fiscal, export and property legislation must become workable, and the need to make a profit must be respected. Nonetheless, foreign investment projects are growing fast. The energy and aeronautics industries are used as case studies of the new possibilities for foreign investors and Russian exporters. Having long been aimed at restricting Russian economic growth, statecraft has become an instrument of growth. The EU's assistance is particularly beneficial as it is non-reimbursable and aims at long-term change through training, yet TACIS could be improved by better management, smaller projects and lower wages. Overall, Western investment in Russian stability should increase