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This paper presents a high speed current differential implementation approach for smart dc distribution systems capable of sub-millisecond fault detection. The approach utilizes the natural characteristics of dc differential current measurements to significantly reduce fault detection times compared to standard applications and hence meet requirements for dc converter protection (around 2ms). Analysis is first developed to help quantify protection implementation challenges for a given dc system. Options for implementing the proposed technique are then illustrated. Results of scaled hardware testing are presented which validate the overall protection operating times in a low voltage environment. These results show the implementation approach can consistently achieve protection system operating within the order of a few microseconds.

Low voltage direct current (LVDC) distribution systems have the potential to support future realization of smart grids and enabling of increased penetration of distributed renewables, electric vehicles, and heat pumps. They do, however, present significant protection challenges that existing schemes based on dc fuses and conventional electro-mechanical circuit breakers cannot manage due to the nature of dc faults and slow device performance. Therefore, this paper presents an advanced protection scheme that addresses the outstanding challenges for protecting an LVDC last mile distribution network. The scheme takes advantage of advanced local measurements and communications that will be naturally integrated in smart grids, and the excellent level of controllability of solid state circuit breakers. It thus provides fast dc fault detection and interruption during dc transient periods, in addition to achieving fault limitation and fast reliable restoration. The introductory part of the paper quantifies the potential benefits of LVDC last mile distribution networks, and discusses the potential LVDC architectures that best utilize the existing plant. Based on the new LVDC architectures, a typical U.K. LV network is energized using dc and modeled, and is used as a case study for investigating the protection issues and evaluating the new protection scheme performance through simulation.

This version is available at https://strathprints.strath.ac.uk/33299/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the AbstractA growing number of designs of future Unmanned Aerial Vehicle (UAV) applications utilise dc for the primary power distribution method. Such systems typically employ large numbers of power electronic converters as interfaces for novel loads and generators. The characteristic behaviour of these systems under electrical fault conditions, and in particular their natural response, can produce particularly demanding protection requirements. Whilst a number of protection methods for multi-terminal dc networks have been proposed in literature, these are not universally applicable and will not meet the specific protection challenges associated with the aerospace domain. Through extensive analysis, this paper seeks to determine the operating requirements of protection systems for compact dc networks proposed for future UAV applications, with particular emphasis on dealing with the issues of capacitive discharge in these compact networks. The capability of existing multi-terminal dc network protection methods and technologies are then assessed against these criteria in order to determine their suitability for UAV applications. Recommendations for best protection practice are then proposed and key inhibiting research challenges are discussed.

The new standard C37.118.1 lays down strict performance limits for phasor measurement units (PMUs) under steady-state and dynamic conditions. Reference algorithms are also presented for the P (performance) and M (measurement) class PMUs. In this paper, the performance of these algorithms is analysed during some key signal scenarios, particularly those of off-nominal frequency, frequency ramps, and harmonic contamination. While it is found that total vector error (TVE) accuracy is relatively easy to achieve, the reference algorithm is not able to achieve a useful ROCOF (rate of change of frequency) accuracy. Instead, this paper presents alternative algorithms for P and M class PMUs which use adaptive filtering techniques in real time at up to 10 kHz sample rates, allowing consistent accuracy to be maintained across a ±33% frequency range. ROCOF errors can be reduced by factors of >40 for P class and >100 for M class devices.