The rapid growth of grid-connected embedded generation is changing the operational characteristics of power distribution networks. Amongst a range of issues being reported in the research, the effect of these changes on so-called 'traditional protection systems' has not gone without attention. Looking to the future, the possibility of microgrid systems and deliberate islanding of sections of the network will require highly flexible distribution management systems and a re-design of protection strategies. This paper explores the envisaged protection issues concerned with large penetrations of embedded generation in distribution networks extending into auto-reclosure and protection device coordination. A critical review of recently reported protection strategies for grid-connected only and microgrid operation is also undertaken. The outcome is a list of recommendations to achieve microgrid protection adequacy in future networks. AbstractThe rapid growth of grid-connected embedded generation is changing the operational characteristics of power distribution networks. Amongst a range of issues being reported in the research, the effect of these changes on so-called 'traditional protection systems' has not gone without attention. Looking to the future, the possibility of microgrid systems and deliberate islanding of sections of the network will require highly flexible distribution management systems and a re-design of protection strategies.This paper explores the envisaged protection issues concerned with large penetrations of embedded generation in distribution networks extending into auto-reclosure and protection device coordination. A critical review of recently reported protection strategies for grid-connected only and microgrid operation is also undertaken. The outcome is a list of recommendations to * Corresponding author Tel. +61 2 42392397 NOTICE: this is the authors' version of a work that was accepted for publication. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. achieve microgrid protection adequacy in future networks.
Highlights d Identification of MCU as a major regulator of phagosomal killing by macrophages d Mice lacking Mcu in myeloid cells are highly susceptible to in vivo candidiasis d Fungal pathogens elicit mCa 2+ elevations using a fast twophase Ca 2+ relay d mCa 2+ signaling activates pyruvate dehydrogenase during phagocytosis
The increased levels of distributed generator (DG) penetration and the customer demand for high levels of reliability have attributed to the formation of the Microgrid concept. The Microgrid concept contains a variety of technical challenges, including load management and anti-islanding protection discrimination strategies. This paper provides a novel scheme in which loads and DG are able to detect the conditions where the load of the island cannot be sufficiently supplied. In these instances, a load shedding algorithm systematically removes loads from the system until an island can be maintained within satisfactory operating limits utilising the local DG. The concept of an Intelligent Load Shedder (ILS) module is proposed in this paper. This module is connected in series with non-critical loads in order to detect the conditions where that nonessential load should be isolated from an island. This module must be capable of communicating with the static transfer switch (STS), which is the intelligent isolator associated with the island. The STS will also be capable of sending and receiving data with each DG's islanding protection device. The combined algorithmic control of the STS, ILS module and DG islanding protection device forms the Intelligent Load Management algorithm. This algorithm is capable of islanding protection and load shedding irrespective of the use of communications. The algorithms within this paper are simulated using MATLAB script. The results show that, on a theoretical level, the intelligent load management scheme described in this paper can be used to detect the conditions where an insufficient load is available using local parameters. Load shedding coordination is also shown to be possible with and without the use of communications between the STS, ILS module and DG islanding protection module. Abstract-The increased levels of distributed generator (DG) penetration and the customer demand for high levels of reliability have attributed to the formation of the Microgrid concept. The Microgrid concept contains a variety of technical challenges, including load management and anti-islanding protection discrimination strategies. This paper provides a novel scheme in which loads and DG are able to detect the conditions where the load of the island cannot be sufficiently supplied. In these instances, a load shedding algorithm systematically removes loads from the system until an island can be maintained within satisfactory operating limits utilising the local DG. The concept of an Intelligent Load Shedder (ILS) module is proposed in this paper. This module is connected in series with non-critical loads in order to detect the conditions where that non-essential load should be isolated from an island. This module must be capable of communicating with the static transfer switch (STS), which is the intelligent isolator associated with the island. The STS will also be capable of sending and receiving data with each DG's islanding protection device. The combined algorithmic control of the STS, ILS...
The proposed algorithm contributes towards an automated power distribution system, which optimally restores the power supply of the network by changing the existing topology, during an unplanned power outage. By automatic reconfiguration of the network, a fault can be isolated and power can be supplied to customers who are downstream of the fault section. BPSO technique has been implemented, which ensures maximum customer connectivity and minimum power losses while maintaining a radial topology which has acceptable voltage profile, allowable thermal limits and protection selectivity. Simultaneously, new protection settings are generated for the proposed network topology, thus preventing any compromise to grid's integrity. The proposed algorithm was tested for an IEEE 33-bus distribution network on MATLAB simulation platform. The generated network configuration achieved an optimal postfault topology. The proposed algorithm automates the process of power restoration and thereby reduces the work for engineers and improves the reliability of distribution networks.
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