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- Habib, Md Zakaria, et al.
(författare)
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Distributed fault-passage indicators versus central fault location : Comparison for reliability centred planning of resonant-earthed distribution systems
- 2023
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Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 9, s. 1731-1742
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Tidskriftsartikel (refereegranskat)abstract
- Fault location methods are crucial for reducing fault restoration time, and thus improving a network's system average interruption duration index (SAIDI) and customer outage cost. Resonant-earthed systems pose problems for traditional fault location methods, leading to poor accuracy and a need for additional complexity. In this context, methods that detect fault direction (fault-passage indicators, FPI) at multiple points in the network may show advantages over a central distance-estimation method using fault locators (FL) of poor accuracy. This paper includes a comparative study of these two major fault location methods, comparing the reliability benefit from a varied number of FPIs or a central method. The optimal placement of the fault locating devices is found by formulating a mixed-integer linear programming (MILP) optimization approach that minimizes both outage and investment costs and assesses SAIDI. This approach has been tested on an example distribution system. However, to justify the universality of the algorithm, the RBTS reliability test system has also been analysed. The comparison of location methods and placement method of FPIs are useful for reliability centred planning of resonant-earthed distribution systems where fault location is to be used. Results show that a small number of FPIs that give accurate identification of direction may give more cost effective increase in reliability than a distance estimate by FL with typical levels of inaccuracy.
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- Habib, Md Zakaria, et al.
(författare)
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Incremental Phase-Current Based Fault Passage Indication for Earth Faults in Resonant Earthed Networks
- 2023
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Ingår i: Electricity. - : MDPI AG. - 2673-4826. ; 4:2, s. 96-113
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Tidskriftsartikel (refereegranskat)abstract
- We propose a method for the fault passage indication of earth faults in resonant-earthed networks, based on phase current measurements alone. This is particularly relevant for electricity distribution systems at medium-voltage levels. The method is based on the relative magnitudes of the phasor changes in the phase currents due to the fault. It is tested for various network types and operation configurations by simulating the network in pscad and using the simulated currents as the input for an implementation of the method in matlab. In over-compensated networks, the method shows reliable detection of the fault passage, with good selectivity and sensitivity for both homogeneous and mixed (cable and overhead line) feeders. However, for the less common under-compensated systems, it has limitations that are described further in this study. The method has good potential for being cost effective since it requires only current measurements, from a single location, at a moderate sampling rate.
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- Hoq, Md Tanbhir
(författare)
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Distance Protection of Transmission Lines with High Levels of Series Compensation : A study on frequency and time domain communication independent distance protection for series compensated lines
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Series capacitors are used in electric transmission lines to increase their power transfer capacity. They compensate for the inductive reactance of the line. They offer a useful alternative to building new lines, in view of economic and environmental constraints. However, during transmission line faults, the presence of series capacitors causes problems for distance protection relays. Distance protection is the most widely used protection method in transmission lines, due to its relatively simple working principle and its ability to work with only local measurements of voltage and current. As the number of series compensated transmission lines is increasing, and the typical compensation level is also increasing, it has become essential to investigate protection methods that can be employed in place of traditional distance protection in series compensated lines.This thesis addresses the problems associated with line protection in the presence of series capacitor compensation. The first part is an assessment of the performance of traditional distance relays in cases with high levels of series compensation. This was based both on simulation studies and on published works describing research studies and industry experience with series capacitor projects and the related line-protection issues. It is concluded that traditional distance protection cannot be used reliably with high levels of series compensation. The second part of the thesis describes some alternative protection methods that are developed and studied as candidates for better single-ended protection of series-compensated lines. These are based on incremental quantities, Lissajous curves and RL/RLC line models. These methods show positive results for single ended protection of series compensated lines.The incremental-quantity based method is fast and operates reliably, but faces under-reach problems with fault resistance. The Lissajous-curve basedmethod can be used as an alternative to the Fourier transform and has some advantages in overcoming inversion situations, but it requires at least a cycle of data to operate. The RL- and RLC-model based solutions can also operate fast, but lose accuracy with higher fault resistances. All the proposed protection methods are extensively tested, using data from fault test cases generated with PSCAD, and algorithms developed in Matlab.
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- Mishra, A, et al.
(författare)
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Diminishing benefits of urban living for children and adolescents' growth and development
- 2023
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 615:7954, s. 874-883
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Tidskriftsartikel (refereegranskat)abstract
- Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
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