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The progressive application of non-linear loads in distribution systems (DS) increases current harmonics flow in DS's apparatuses, especially distribution transformers (DTs). Since DTs' operating temperature rises due to the harmonics flow, their loading should be reduced such that the hot spot temperature (HST) is preserved under its permissible value. This means that DTs' available capacity is influenced by load harmonic content. In this paper, a novel formulation for DTs' failure rate in the presence of harmonics is presented as a function of load harmonic contents. Using the suggested equivalent failure rate, DTs' available capacity in harmonic polluted DS is mathematically formulated. Additionally, the presence of the harmonic increases the HST, leading to DTs' aging acceleration. Therefore, the impact of harmonic components on DTs' aging is arithmetically modeled. To evaluate the efficacy of the suggested reliability model, it is applied to three distinct DTs having respectively industrial, commercial, and residential loads. The obtained results indicate that the available capacity of DTs with the same rated capacity would be different regarding to their load harmonic contents. On the other hand, it is comprehended from the achieved results that the aging acceleration factor (Faa) of the DTs increases owing to their load harmonic contents. [ABSTRACT FROM AUTHOR]

Using doubly-fed induction generator (DFIG) based onshore wind farms in power systems may lead to mal-operation of the second zone (Z2) of distance protection due to the uncertain number of available wind turbines on the one hand and the function of DFIGs control system to maintain the bus voltage on the other hand. In such cases, variable injected current by the wind farm causes distance relay fall in trouble to distinguish whether the fault point is in the Z2 operating area or not. In the current study, an adaptive settings scheme is proposed to determine the Z2 setting value of distance relays for such cases. The proposed method is based on the adaptive approach and the settings group facility of the commercial relays. The proposed method applies the k-means clustering approach to decrease the number of setting values calculated by the adaptive approach to the number of applicable settings group in the distance relay and uses the Particle Swarm Optimization (PSO) algorithms to achieve the optimum setting values. The high accuracy of the proposed method in comparison with other methods, suggested in the literatures, is shown by applying them to the IEEE 14-bus grid. [ABSTRACT FROM AUTHOR]

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Optimal placement and sizing of distributed renewable energy resources (DER) in distribution networks can remarkably influence voltage profile improvement, amending of congestions, increasing the reliability and emission reduction. However, there is a challenge with renewable resources due to the intermittent nature of their output power. This paper presents a new viewpoint at the uncertainties associated with output powers of wind turbines and load demands by considering the correlation between them. In the proposed method, considering the simultaneous occurrence of real load demands and wind generation data, they are clustered by use of the k-means method. At first, the wind generation data are clustered in some levels, and then the associated load data of each generation level are clustered in several levels. The number of load levels in each generation level may differ from each other. By doing so the unrealistic generation-load scenarios are omitted from the process of wind turbine sizing and placement. Then, the optimum sizing and placement of distributed generation units aiming at loss reduction are carried out using the obtained generation-load scenarios. Integer-based Particle Swarm Optimization (IPSO) is used to solve the problem. The simulation result, which is carried out using MATLAB 2016 software, shows that the proposed approach causes to reduce annual energy losses more than the one in other methods. Moreover, the computational burden of the problem is decreased due to ignore some unrealistic scenarios of wind and load combinations. [ABSTRACT FROM AUTHOR]

Background This study aimed to evaluate the role of H2S on gastric emptying rate ( GER) and also to determine the effect of gastric distention on mRNA and protein expression of cystathionine β-lyase ( CBS) and cystathionine γ-synthase ( CSE) in diabetic-gastroparetic and normal rats. Methods Adult normal rats intraperitoneally received either propargylglycine ( PAG), L-cysteine or Na HS 30 min prior to GER marker (acetaminophen) to investigate H2S involvement in GER and the same protocols were performed in diabetes-induced gastroparesis rats. The role of calcitonin gene related peptide ( CGRP) neurons in the prokinetic effect of endogenous H2S on GER was determined. The level of CBS and CSE expressions in response to gastric distention were also determined. The effect of H2S on frequency and tension of spontaneous contractions of gastric smooth muscle strips was investigated. Key Results Our results showed that: (i) H2S and L-cysteine increased GER in gastroparetic and normal rats. (ii) The increased levels of CSE expression in response to gastric distention in diabetic rats were lower than in normal rats. (iii) PAG inhibited the excitatory effect of capsaicin on GER and on tension of spontaneous contractions of strips. (iv) Hydrogen sulphide increased the frequency and tension of spontaneous contractions of gastric strip muscles in normal and diabetic rats. Conclusions & Inferences The results showed that delayed GER in diabetic rats can be due to down-regulation of H2S biosynthesis enzyme, CSE and suggested that a potential prokinetic role for H2S to treat the delayed gastric emptying in diabetic patients. [ABSTRACT FROM AUTHOR]

Behaviour of upright suction caissons with regard to their applications, installation, load-bearing, etc., has already been investigated by a number of researchers. Some researchers have also addressed the behaviour of tapered piles under different loading conditions. However, there has not been any previous experimental experience regarding the performance of tapered suction caissons. This paper reports the results of a primarily experimental investigation intended as a first step to understanding the performance of tapered suction caissons. The 1g experiments have been carried out on small-scale caisson models having upright and sloping walls. The caissons have been installed in a very fine saturated silty sand, and the effects of geometrical parameters, wall slope and the soil density on the overall penetration force required for installation and the pull-out capacity of the cassion have been studied. Influence of pull-out rate on the ultimate capacities has also been investigated. [ABSTRACT FROM AUTHOR]

Chandra and Abha [European J. Oper. Res. 122 (2000), 161-165] considered a nonlinear programming problem over cone constraints and presented the correct forms of its four types of duals formulated by Nanda and Das [European J. Oper. Res. 88 (1996) 572-577]. Yang et al. [Indian J. Pure Appl. Math. 35 (2004), 699-708] considered the same problem and discussed weak and strong duality for its four types of second order duals under the assumptions of generalized second order F-convexity. In this paper, we are intended to prove converse duality theorems for second order duals of Yang et al. [ABSTRACT FROM AUTHOR]