Lateral Feeder Research Articles

Sustained Coordination of Devices in a Two-Layer Protection Scheme for DGs-Integrated Distribution Network Considering System Dynamics

Distribution networks are usually protected by directional overcurrent relays (DOCRs). Besides, autoreclosers and fuses can be used for protecting lateral feeders to minimize power cuts. Coordinated operation of protection device must be maintained to ensure optimal fault isolation. Typically, steady-state fault current and static protective device characteristics are used to determine optimal settings of devices such that coordinated operation is verified. Sine fault current is not a steady signal and protection devices have dynamic behaviors, the conventionally-determined settings of devices can lead to loss of coordination jeopardizing system reliability. In this paper, a two-layer protection scheme is proposed for a distribution network with distributed generators (DGs). The first layer has DOCRs to protect main feeders. The second has autoreclosers and fuses to protect lateral feeders. Optimal settings of devices are determined to achieve both local-layer and inter-layer coordination of devices by constrained nonlinear optimization. Full dynamic models of every component and transient data of fault current are considered. Furthermore, to sustain coordination under DGs, a hybrid superconducting fault current limiter (HSFCL) with high temperature superconducting resistive element is connected in series to each DG. Dynamic modeling-based HSFCL cost minimization is searched by multi-objective optimization. The approach is applied to two distribution networks and simulation results are analyzed.

Voltage Estimation Method for Power Distribution Networks Using High-Precision Measurements

In this study, we propose a voltage estimation method for the radial distribution network with distributed generators (DGs) using high-precision measurements (HPMs). The proposed method uses the section loads center for voltage estimation because individual loads are not measured in the distribution system. The bus voltage was estimated through correction of the section load center by using an HPM at the end of the main feeder. The correction parameter of the section load center was calculated by comparing the initial voltage estimates and the measurements of the HPMs. After that, the voltage of the main feeder was re-estimated. Finally, the bus voltage in the lateral feeder was estimated based on the voltage estimates in the main feeder and the current measurements in the lateral feeder. The accuracy of the proposed algorithm was verified through case studies by using test systems implemented in MATLAB, Simulink, and Python environments. In order to verify the utilization of the proposed method to the practical system, a test with injection of approximately 5% of normally distributed random noise was performed. Through the results of the case studies, when an HPM is installed at the end of the main feeder, it demonstrated that the voltage estimation accuracy can be greatly improved by the proposed method. Compared with the existing methods, the proposed method was less affected by PV and showed robustness to measurement noise.

A Method for Estimating Technical Losses in Primary Feeder Conductors

One of the engineers’ concerns is the loss of energy in the electric power system. Actually, most of the energy losses occur in the distribution system, i.e., about 4-8%. Therefore, efforts should be made in order to improve the performance of the distribution networks. Evaluating losses in the distribution networks should be done in order to reduce losses. The problem is that there are many nodes, several lateral feeders, and the un-uniform current flowing in the feeder so that calculating the losses becomes very difficult. In addition, the big distribution system has so many feeders, generally more than 1000 feeders, with various types. Thus, the calculation of the losses in the distribution system will face very complex and large-scale problems. Therefore, calculating losses for large scale distributed systems that use load flow or measurement methods is not possible. This paper proposes an effective method that uses a lump load model for technical losses in distribution systems. By approaching, the current is proportional to power, the input current into the feeder can be distributed to each lateral feeder. Thus, the current flow in each segment of the feeder can be determined. For typical feeder with the load currents changed linearly by linearity factor, then-current flows of each segment feeder can be easily determined as c function. This function is created as a calculation model of losses with a clear derivative of the mathematical formulations. The results of numerical studies show that this method is accurate enough with the error of 1.26% when compared to the load flow method using an 8-node feeder. The calculation result is based on the IEEE 13-node test feeder; its loss is smaller than 3.86% compared to the load flow method.

Fault Location Method Using Phasor Measurement Units and Short Circuit Analysis for Power Distribution Networks

This paper proposes a fault location method for power distribution networks using phasor measurement units (PMU) and short circuit analysis. In order to improve the problems of the existing studies, we focused on several approaches as follows. First, in order to minimize the number of PMU installations, a fault location estimation of lateral feeders through short circuit analysis was presented. Second, unbalanced faults and impacts of photovoltaic (PV) were considered. The proposed method consists of two stages. In Stage 1, the fault location was estimated for the main feeder using PMU installed at the start and end points of the main feeder. Symmetrical components of voltage and current variation were calculated by considering the impact of PVs interconnected to the lateral feeders. If the result of Stage 1 indicated a connection section of lateral feeder on the main feeder, Stage 2 would be performed. In Stage 2, the fault location was estimated for the lateral feeder by comparing the results of the short circuit analysis and measurements of PMUs. The short circuit analysis was based on an unbalanced power flow that considered dynamic characteristics of the PV inverter. The proposed method was verified through various fault situations in a test system. For the applicability of the proposed algorithm to the actual system, a noise test was also performed.

Decentralized three-phase distribution system static state estimation based on phasor measurement units

This paper presents a novel approach for static state estimation in electrical distribution systems, in which the state variables to be estimated are branch currents in rectangular coordinates. Branch current and voltage phasors are measured from a reduced number of PMUs located along a non fully observable electrical distribution system with radial topology. For the non-monitored buses, load pseudo-measurements are considered as a set of inequality constraints varying between upper and lower limits, which are adjusted during the safety barrier interior point optimization solution process (SBIPM). In order to track daily load variations, the initial load limits for the next time interval are obtained from the actual estimated loads at the non-monitored buses, considering the percentage of power variation at the exit of each lateral feeder. At each iteration of the SBIPM solution process, if any load is set to its corresponding limit, then a new limit margin is set accordingly, meaning that at the end of the solution process all the non-monitored loads are within specified bounds. The distribution network is also subdivided into subsystems considering a PMU allocation procedure in which each lateral feeder is estimated individually, yielding a naturally decentralized state estimator. In this decentralization context, priority loads, such as hospitals, police stations, telecom centers and places with high load density concentration can be considered as monitored subareas, exploring the radial topology of the distribution system. Tests are conducted on IEEE 33 bus test feeder and compared with an existing method in the literature to show the effectiveness of the proposed algorithm. Another simulation was conducted on a long lateral feeder of 57 bus in order to show the possibility of using the proposed technique for large scale distribution systems.

The relationship between forceful and passive emplacement: The interplay between tectonic strain and magma supply in the Rosses Granitic Complex, NW Ireland

The Rosses Granitic Complex, NW Ireland, part of the late Caledonian (c. 400 Ma) Donegal Batholith, provides the opportunity to study the interplay between relative tectonic strain and magma supply rates in the wall of a major tectonic shear zone. Anisotropy of magnetic susceptibility (AMS) measurements, structural analysis and examination of key intrusive relationships were used to assess the accommodation of magma, associated deformation and magma flow pathways in this complex. In this case the varying emplacement styles, switching from forceful to passive, indicate that relative tectonic strain and magma supply rates were not constant. In the earliest component (a suite of microgranite sheets), AMS reveals subtle fabrics discordant to the sheet margins and is interpreted as post-emplacement deformation fabrics. The concordance of these fabrics to the next component of the complex, the main pluton (G1 and G2 monzogranite), indicates that this deformation was caused by the forceful emplacement of the pluton. AMS fabrics in G1 and G2 reveal a dome shaped foliation with an east-west lineation, indicating an east-west oriented magma transport direction. Outcrops of small stocks or cupolas similar to G2, east of the main pluton, link it to similar lithologies in the Main Donegal Granite further to the east via a partially exposed lateral feeder. This suggests east to west emplacement. The next component, a suite of subvertical porphyritic felsite dykes, is shown (from AMS and visible shearing fabrics) to have been emplaced passively under east-west tension. The final component comprises G3 and G4 of the main pluton, which passively cut all earlier components and contains significant amounts of aplite, pegmatite and greisen. These are interpreted to be cupolas or stocks emanating from an unexposed sheet probably similar in composition and mode of emplacement to G1 and G2. Thus, a general model is put forward where initially forceful subhorizontal sheets extending laterally from the nearby Main Donegal Granite shear zone, gave way to passive emplacement where the roofs of these and subjacent sheets failed. The control on siting of the complex can be related to lower crustal structures, which control upper crustal shear zones. The reason for the switch in emplacement style is suggested to be due to a waning magma supply, in a tectonic strain field where the extensional component was oriented east-west. The waning magma supply then possibly due to switching of the site of emplacement of magma, supplied by the Main Donegal Granite shear zone, to another member of the Donegal Batholith – the Trawenagh Bay Granite.

Magmatic flow paths and palaeomagnetism of the Miocene Stoddard Mountain laccolith, Iron Axis region, Southwestern Utah, USA

Abstract The Stoddard Mountain laccolith is part of a complex of Early Miocene laccoliths intruded along the western edge of the Colorado Plateau in the Iron Axis region of Southwestern Utah. Most Colorado Plateau laccoliths (e.g. Henry and La Sal Mountains) are considered to be fed by a central axial feeder system. However, detailed mapping in the Iron Axis region suggests that the Stoddard Mountain laccolith was fed laterally from the west. Structural and field data suggest the quartz monzonitic magma initially migrated laterally eastward at ∼1 km depth as a sill before spreading laterally north-south where it inflated to ∼1–1.5 km thickness. To test the model of a lateral feeder system, data were collected from 32 palaeomagnetic sites and 76 AMS stations (763 accepted specimens) sampled over the ∼54 km 2 exposed part of the N-S oval-shaped laccolith. The in situ AMS fabrics, inferred to correlate with magmatic fabrics, typically show NE trending lineations in the north and S-SE trending lineations in the south part of the intrusion. The palaeomagnetic data are interpreted to indicate a very minimal amount of post-emplacement deformation of the intrusion. The overall lack of westerly-directed and steep magnetic lineations argues against emplacement via a central axial feeder system.

Palaeoenvironmental reconstruction of dinosaur nesting sites based on a geochemical approach to eggshells and associated palaeosols (Maastrichtian, Provence Basin, France)

Variability of the stable isotopic (δ 13C and δ 18O) and trace element (Mg, Sr, Fe, and Mn) content from dinosaur eggshells from the Provence Basin has been addressed by considering the stratigraphic distribution of the eggshells, the palaeoenvironments, and the chemical content of associated sediments. Preferentially, in situ eggshells were analysed. Samples were collected from two sections, one belonging to the floodplain (Roques Hautes) and the other to the channel belt (Rousset–Bréguières), as determined from sedimentological criteria. On a regional scale, this combined analysis provided new insights into palaeohydrology, vegetation cover and dinosaur behaviour. Different sources of drinking water were identified: (1) the main stream waters with significant salinity levels, (2) lateral feeders with water composition close to that of precipitation. Water composition is reflected in the eggshell trace element contents: a high Sr content for the eggshells from the channel belt (mean 1200 ppm) contrasting with the very low values for the floodplain (mean 250 ppm). During the first part of the Maastrichtian, evaporation rates were quite significant, as seen from the 1.5‰ difference between the eggshell δ 18O (drinking water) and the palaeosol carbonate nodules (precipitation). This contrast diminished and became nearly insignificant in the second half of the Maastrichtian. Vegetation was composed of C 3 plants and two ecosystems are reconstructed: a riparian forest extending along the channel belt and open vegetation in the floodplain. The contrasted isotopic and trace element content of the eggshells was a crucial factor in identifying animal migration from one site to another. Migration was quite limited, suggesting that the animals settled for some time at the places where they laid their eggs. Intraspecific variations among modern birds are well correlated with the environment and may be greater than interspecies variations, which limits the potential of geochemical analysis to characterise dinosaur species.

A comparison between subaerial and submarine eruptions at Kilauea Volcano, Hawaii: implications for the thermal viability of lateral feeder dikes

Eruption styles on the subaerial East Rift Zone (ERZ) of Kilauea volcano are reviewed and a classification scheme for the different types of eruption is proposed. The various eruption types are produced by differing thermal and driving pressure behaviour in the feeder dikes. Existing evidence is reviewed and new evidence presented of the types and volumes of eruptions on the Puna Ridge, which is the submarine extension of the ERZ. Eruptions on the Puna Ridge fall into the same five classes as, and are of comparable volume to, those on the subaerial ERZ. Evidence is presented which suggests that feeder dikes for Puna Ridge eruptions are more thermally viable than those feeding subaerial eruptions, and this difference causes long-lived, large-volume eruptions to be more common on the Puna Ridge than on the subaerial ERZ. This systematic variation in thermal viability may be due to increased dike width for Puna Ridge dikes or increased pressure gradients driving magma flow. Lateral dike emplacement is common to many basaltic systems including on other Hawaiian volcanoes, in Iceland and at mid-ocean ridges. The systematic trend inferred for the ERZ of Kilauea implies that in the other systems large-volume eruptions may also be more common at great distances than they are close to the magma centre.

Feeding Arteries of Parasellar Meningiomas

The feeding arteries of 14 parasellar meningiomas treated between 1962 and 1985 were analyzed. Nine were medial sphenoid ridge meningiomas (four of the alar type and five of the clinoidal type) and five were tuberculum sellae meningiomas. Retrospective analysis of the arteries supplying the basal dura of the involved region revealed diverse dural branches originating from both the internal and external carotid systems in this region. These arteries were classified as anterior, posterior, or lateral. Two of the four alar type meningiomas were supplied by lateral feeders, and two by both anterior and lateral feeders. One of the five clinoidal meningiomas was fed by anterior and lateral arteries, and one by posterior arteries. No feeding arteries were identified in the three remaining cases of clinoidal meningioma. Three of the five tuberculum sellae meningiomas had anterior feeders, one had posterior feeders, and one had no angiographically detectable feeders. The tumors of three patients in this series were found to be supplied by both the internal and external carotid systems. It can be concluded that there is a relationship between the sites of parasellar tumors and the internal and external carotid arteries that feed them.

Root rot caused by Pythium irregulare Buisman, an important factor in the decline of established subterranean clover pastures

The problem of poor re-establishment and poor seasonal production in long-term subterranean clover pastures has been recognized for some time, particularly on the Southern Tableland and Slopes regions of New South Wales. Field and laboratory investigations showed that rotting of the lateral feeder roots was a common disease of subterranean clover during the cool part of the growing season. Isolations made from diseased roots yielded a predominance of Pythium spp. of which Pythiurn irregulare was the most common. Pathogenicity tests demonstrated that P. irregulare consistently caused damping-off of germinating subterranean clover. This fungus also infected established plants and at low temperatures caused severe reduction of dry matter production. Symptoms produced on artificially inoculated plants were identical with those observed on plants infected in the field. Soil moisture and the level of fungal inoculum added did not have a critical effect on the severity of root disease. A range of other important pasture and crop species were also artificially infected with P. irregulare, with resulting necrosis of feeder roots. In vitro studies of factors affecting the growth of P. irregulare showed that this pathogen was well adapted to survive and cause disease in cold wet soils, the conditions most favourable for root rot in the field. The importance of P. irregulare as a pathogen of established plants and possible means of reducing its effect on the growth of subterranean clover are discussed.

Characters for Separating Larvae of Sitona lineata (L.) and Sitona hispidula (Coleoptera: Curculionidae)

The pea leaf weevil (Sitona lineata (L.)), a European pest of legumes, was found by W. Downes (1938) in British Columbia in 1936 where it appears to have been introduced by accident. It has gradually moved southward to legume-producing areas of western Washington and Oregon. In this region its populations have become mixed with those of the clover root curculio (Sitona hispidula (F.)) and thus a need was created for data that would be of aid to field workers in separating the two species. The adults of both species have been adequately described by Jackson (1920). Differences such as the comparatively slender body of lineata, its recumbent elytral bristles, and its quick, excitable movements contrast with the robust appearance, semi-erect elytral bristles, and slower movements of hispidula so that separation in the adult stage offers no serious problem. The larval stages of both species feed underground upon the root systems of the plants they infest. S. hispidula consumes the small lateral feeder roots of clovers and alfalfa, and most economic damage is produced by this species in its larval stage.