The effect of fault ride-through requirements on voltage dips and post-fault voltage recovery in a Dutch distribution network

In this paper the possibility to use Decentralized Generation (DG) units for voltage support in Distribution Networks during and after a Short Circuit (S/C) event is discussed. Two types of DG units will be examined, Combined Heat-Power (CHP) plants and Doubly-Fed Induction Generators (DFIG). Earlier approaches would oblige the disconnection of these units during grid disturbances, in order to avoid unwanted conditions such as interference with the protection system and islanding [1]. Newer grid codes for Transmission Networks like [2], taking into consideration the increased share of these units in energy production have set specific Fault Ride-Through (FRT) criteria which oblige them to stay connected during SC events when they are combined to large plants directly connected to the transmission grid, such as (off shore) wind farms.. If ever more DG is connected directly to distribution grids, the same reasoning leading to applying rault ride through criteria to DG connected in large groups to transmission grids, may be applied to DG connected to distribution grids, as a loss of a a large amount of DG connected to distribution grids has the same adverse effect as using DG connected directly to the transmission grid

Evaluating testcross performance and genetic divergence of lines derived from reciprocal tropical maize composites

The development of hybrids with enhanced expression of heterosis depends on the genetic background of the source population and the effectiveness of a breeding scheme used to identify and use divergent inbred lines with good combining ability. The present study was conducted to examine the potential of improved tropical reciprocal composites as sources of inbred lines for developing productive hybrids. Thirty-six S4 lines derived from the third RRS cycle of each composite were crossed in pairs to form 36 testcrosses, which were evaluated along with commonly grown commercial hybrids in Nigeria across nine test environments. Results showed consistent ranking of testcrosses for grain yield and other traits across the diverse test environments. The best 22 testcrosses produced 21% to 51% more grain yields than the highest yielding commercial hybrid. Several testcrosses combined high grain yields with other desirable agronomic traits. The SSR and SNP markers used in the present study detected a broad range of genetic diversity among the 72 S4 lines, which was structured along the two composites. The two markers portrayed similar trends in determining genetic distance estimates and detecting composite-specific alleles in the S4 lines. These results highlight the potential of improved reciprocal composites as sources of new and divergent parents for developing productive hybrids and as sources of novel alleles for broadening and diversifying the genetic base of adapted germplasm to sustain genetic gain in productivity of hybrids in WCA

Unlocking the hidden potentioal of electricity distribution grids

For the grid, electric vehicles can be seen as flexible loads since they stand still for at least 90% of the time. The coupling of these flexible loads to the grid can bring advantages for the power system. However, to connect electric cars enough capacity is needed. Already existing capacity might be made available for this extra load by using the flexibility of the electric vehicles and controlling them well. This paper describes an analysis of the existing capacity of the distribution grid of Enexis B.V. which might become available for flexible loads if they are coupled to the grid in an intelligent way. The available capacity of a part of the distribution grid owned and operated by Enexis B.V. is estimated, based on measured data. Further, it is described how this capacity can be used by flexible loads. It is also briefly discussed how this can be facilitated by the introduction of the so-called ‘Mobile Smart Grid’, which includes secondary systems to control the load

Changes in heterosis of maize (Zea mays L.) varietal cross hybrids after four cycles of reciprocal recurrent selection

Two improved tropical maize composites, TZL COMP3 and TZL COMP4; representing complementary heterotic pools have been subjected to four cycles of reciprocal recurrent selection (RRS) for two decades to enhance varietal cross performance. The objectives of this study were to evaluate the effect of selection on genetic gain in heterosis for grain yield and other agronomic traits of these composites. Ten parental populations representing the C0 to C4 of each composite and their crosses plus a varietal check were evaluated in a trial at eight environments in Nigeria. Grain yield of the varietal crosses increased with selection by 3.1% cycle–1. Mean grain yields of the C4 × C4 varietal cross exceeded that of a popular improved reference variety by 23%. Selection also reduced anthesis-silking interval, improved ear characteristics, phenotypic appeal and resistance to foliar diseases. Mid-parent heterosis (MPH) increased from 4% at C0 × C0 to 24% at C4 × C4. The average rate of genetic gain in heterosis for grain yield in population crosses was 3.1% possibly because of presence of non-additive gene effects. The results of our study present the potential usefulness of the advanced selection cycle as sources of diverse inbred lines with improved combining ability as well as improved varietal crosses that can be multiplied and deployed in areas with limited market access

Response of MV-connected Doubly-Fed Induction Generator wind turbines and CHP-plants to grid disturbances

Notwithstanding the positive environmental impact, the increasing penetration of Distributed Generation (DG) units connected to the distribution network raises new topics concerning the expected response of these during outages. Grid disturbances especially at the transmission level can cause the unwanted disconnection of large amounts of DG, leading to undesired power imbalances causing line overloadings and/or voltage and frequency instability. This paper examines how transmission network faults can affect the operation of DG units connected on to the distribution network, how these units currently contribute to the voltage support and what are the consequences of actual and possible Fault Ride-Through (FRT) behaviors

Advances in screening methods and breeding for resistance to downy mildew and stem borers in maize

Maize is the most important cereal in sub-Saharan Africa. It is relatively inexpensive and provides many families with much-needed nutrients. For the farmers, it matures early and Is a source of ready income. Maize production Is being threatened by some diseases and pests, among which are downy mildew and stem borers. Serious yield losses often occur. This paper summarizes two studies that report the efforts of liT A scientists to screen and breed maize varieties for resistance to downy mildew and stem borers

Acoustic instrumentation for a bubble chamber towards dark matter searches

Dark matter is one of the top unsolved mysteries in physics. Its existence is well-established although its nature remains unknown. Despite the progress made in the direct search effort, reflecting over 10 orders of magnitude in sensitivity since 1984, no true candidates to explain this phenomenon have appeared in searches covering a range from ~10 GeV to 1 TeV. This article reports on the development of a 1 kg freon bubble chamber prototype, including the chamber recompression system design and testing, initial acoustic detection of bubble formation, and initial neutron and alpha detector response studies. The prototype constructed was a transparent acrylic containment vessel, capable of withstanding recompression cycles to a pressure of 16 bar. The acoustic signal accompanying bubble formation was investigated using three different sensors: a low frequency microphone (Panasonic) with a flat response over 0.020-16 kHz, an ultrasound externallypolarized condenser microphone (AviSoft) with a flat response over 10-150 kHz, and an hydrophone (Reson) with a flat response over 5-170 kHz. Acoustic signatures of several induced events were successfully registered. The data acquisition digitizer used, to meet the range of the three microphones, was the NI PCI-6251 16-Bit, with at least 1.25 MSps for 1-Channel

New hyperekplexia mutations provide insight into glycine receptor assembly, trafficking, and activation mechanisms

Background: Hyperekplexia mutations have provided much information about glycine receptor structure and function. Results: Weidentified and characterized nine new mutations. Dominant mutations resulted in spontaneous activation, whereas recessive mutations precluded surface expression. Conclusion: These data provide insight into glycine receptor activation mechanisms and surface expression determinants. Significance: The results enhance our understanding of hyperekplexia pathology and glycine receptor structure-function. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc. Published in the U.S.A