International White Book on DER Protection : Review and Testing Procedures

This white book provides an insight into the issues surrounding the impact of increasing levels of DER on the generator and network protection and the resulting necessary improvements in protection testing practices. Particular focus is placed on ever increasing inverter-interfaced DER installations and the challenges of utility network integration. This white book should also serve as a starting point for specifying DER protection testing requirements and procedures. A comprehensive review of international DER protection practices, standards and recommendations is presented. This is accompanied by the identifi cation of the main performance challenges related to these protection schemes under varied network operational conditions and the nature of DER generator and interface technologies. Emphasis is placed on the importance of dynamic testing that can only be delivered through laboratory-based platforms such as real-time simulators, integrated substation automation infrastructure and fl exible, inverter-equipped testing microgrids. To this end, the combination of fl exible network operation and new DER technologies underlines the importance of utilising the laboratory testing facilities available within the DERlab Network of Excellence. This not only informs the shaping of new protection testing and network integration practices by end users but also enables the process of de-risking new DER protection technologies. In order to support the issues discussed in the white paper, a comparative case study between UK and German DER protection and scheme testing practices is presented. This also highlights the level of complexity associated with standardisation and approval mechanisms adopted by different countries

Doktrin pengasingan kuasa : falsafah, praktis dan kerelatifan di Malaysia

Penulisan ini membincangkan tentang doktrin pengasingan kuasa berdasarkan kerangka teori institusionalisme. Doktrin ini dipraktiskan dalam trias politica atau politik tiga serangkai iaitu badan legislatif, eksekutif dan kehakiman. Falsafah dan praktis doktrin pengasingan kuasa ini adalah ditekankan bagi sesebuah negara bercorak demokrasi untuk mempamerkan wujudnya pengasingan kuasa serta autonomi bidangan di antara ketigatiga badan kerajaan. Hal ini penting untuk disoroti kerana Malaysia tidak terkecuali daripada mengamalkan sistem demokrasi dan pada masa yang sama mempraktiskan doktrin pengasingan kuasa dalam kerajaan federalisme berlapisnya sebagai satu pegangan fundamental. Akauntabiliti untuk menzahirkan doktrin pengasingan kuasa ini merupakan perkara yang penting memandangkan ia telah dimaktubkan dalam Perlembagaan Persekutuan

Implications of fault current limitation for electrical distribution networks

This paper explores the potential future need for fault current limitation in the UK's power system, and some of the technical implications of this change. It is estimated that approximately 300-400 distribution substations will require fault current limitation, based on the statistical analysis of the projected fault level "headroom" (or violation). The analysis uses a UK electrical system scenario that satisfies the Government's target for an 80% cut in CO2 emissions by 2050. A case study involving the connection of distributed generation (DG) via a superconducting fault current limiter (SFCL) is used to illustrate the potential protection and control issues. In particular, DG fault ride-through, autoreclosure schemes, and transformer inrush current can be problematic for SFCLs that require a recovery period. The potential solutions to these issues are discussed, such as the use of islanding or automation to reduce the fault level

An Adaptive Overcurrent Coordination Scheme to Improve Relay Sensitivity and Overcome Drawbacks due to Distributed Generation in Smart Grids

Distributed Generation (DG) brought new challenges for protection engineers since standard relay settings of traditional system may no longer function properly under increasing presence of DG. The extreme case is coordination loss between primary and backup relays. The directional overcurrent relay (DOCR) which is the most implemented protective device in the electrical network also suffers performance degradation in presence of DG. Therefore, this paper proposes the mitigation of DG impact on DOCR coordination employing adaptive protection scheme (APS) using differential evolution algorithm (DE) while improving overall sensitivity of relays . The impacts of DG prior and after the application of APS are presented based on interconnected 6 bus and IEEE 14 bus system. As a consequence, general sensitivity improvement and mitigation scheme is proposed

Enhancing reliability in passive anti-islanding protection schemes for distribution systems with distributed generation

This thesis introduces a new approach to enhance the reliability of conventional passive anti-islanding protection scheme in distribution systems embedding distributed generation. This approach uses an Islanding-Dedicated System (IDS) per phase which will be logically combined with the conventional scheme, either in blocking or permissive modes. Each phase IDS is designed based on data mining techniques. The use of Artificial Neural Networks (ANNs) enables to reach higher accuracy and speed among other data mining techniques. The proposed scheme is trained and tested on a practical radial distribution system with six-1.67 MW Doubly-Fed Induction Generators (DFIG-DGs) wind turbines. Various scenarios of DFIG-DG operating conditions with different types of disturbances for critical breakers are simulated. Conventional passive anti-islanding relays incorrectly detected 67.3% of non-islanding scenarios. In other words, the security is as low as 32.3%. The obtained results indicate that the proposed approach can be used to theoretically increase the security to 100%. Therefore, the overall reliability of the system is substantially increased

Reconfiguration of power networks based on graph-theoretic algorithms

The intentional area partitioning and automated distribution system restoration are two important Smart Grid technologies to enhance the robustness of a power network and improve the system reliability. In this dissertation, the research work is focused on deriving and implementing efficient graph-theoretic algorithms to analyze and solve such two real-world problems in power systems as follows. In response to disturbances, a self-healing system reconfiguration that splits a power network into self-sufficient islands can stop the propagation of disturbances and avoid cascading events. An area partitioning algorithm that minimizes both real and reactive power imbalance between generation and load within islands is proposed. The proposed algorithm is a smart grid technology that applies a highly efficient multilevel multi-objective graph partitioning technique. The simulation results obtained on a 200- and a 22,000- bus test systems indicate that the proposed algorithm improves the voltage profile of an island after the system reconfiguration compared with the algorithm that only considers real power balance. In doing so, the algorithm maintains the computational efficiency. The distribution system restoration is aimed at restoring loads after a fault by altering the topological structure of the distribution network by changing open/closed states of some tie switches and sectionalizing switches in the distribution system. A graph-theoretic distribution system restoration strategy that maximizes the amount of load to be restored and minimizes the number of switching operations is developed. Spanning tree based algorithms are applied to find the candidate restoration strategies. Unbalanced three-phase power flow calculation is performed to guarantee that the proposed system topology meets all electrical and operational constraints. Simulation results obtained from realistic feeder models demonstrate the effectiveness of the proposed approach