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The massive worldwide use of antibiotics leads to water pollution and increasing microbial resistance. Hence, the removal of antibiotic residues is a key issue in water remediation. Here, we report the solar light-assisted oxidative degradation of ciprofloxacin (CPF), using H2O2 in aqueous solution, catalyzed by iron(III) chelated cross-linked chitosan (FeIII-CS-GLA) immobilized on a glass plate. The FeIII-CS-GLA catalyst was characterized by FTIR and 57Fe-Mössbauer spectroscopies as well as X-ray diffraction, revealing key structural motifs and a high-spin ferric character of the metal. Catalytic degradation of CPF was investigated as a function of solar light irradiation time, solution pH, concentration of H2O2 and CPF, as well as cross-linker dosage and iron(III) content in FeIII-CS-GLA. The system was found to serve as an efficient catalyst with maximum CPF degradation at pH 3. The specific ·OH scavenger mannitol significantly reduces the degradation rate, indicating that hydroxyl radicals play a key role. The mechanism of catalytic CPF degradation was evaluated in terms of pseudo-first-order and Langmuir-Hinshelwood kinetic models; adsorption of CPF onto the FeIII-CS-GLA surface was evidenced by field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. FeIII-CS-GLA can be reused multiple times with only minor loss of catalytic efficiency. Antimicrobial activity tests performed against both Gram-negative (Escherichia coli DH5α, Salmonella typhi AF4500) and Gram-positive bacteria (Bacillus subtilis RBW) before and after treatment confirmed complete degradation of CPF. These results establish the immobilized FeIII-CS-GLA as a rugged catalyst system for efficient photo-Fenton type degradation of antibiotics in aqueous solutions. [ABSTRACT FROM AUTHOR]

Textile and food industries produce a significant volume of effluents containing azo dyes and other pollutants. These effluents are serious environmental threats, and new methods for their treatment and for the degradation of azo dyes are thus attracting much attention. The current study deals with the oxidative degradation of azo dyes by meso‐tetrakis(1‐methylpyridinium‐4‐yl)prophyrinatoiron(III), [FeIII(tmpyp)], and meta‐chloroperoxy benzoic acid (m‐CPBA) in aqueous solution at room temperature. The catalytic degradation of azo dyes was investigated by using rapid‐scan stopped‐flow spectrophotometry as a function of solution pH, [catalyst], [m‐CPBA], [dye] and [surfactants]. To obtain mechanistic insight, the reaction between [FeIII(tmpyp)] and m‐CPBA was also studied in aqueous solution in absence of azo dyes. Spectral analyses and kinetic data show that [FeIII(tmpyp)] is transformed into the transient intermediate [FeIV(O)(tmpyp)].+ (a compound I analog) within 20–30 ms followed by the formation of relatively stable [FeIV(O)(tmpyp)] (a compound II analog). Batch experiments reveal that the dye degradation rate is influenced by the solution pH and the concentrations of [FeIII(tmpyp)], m‐CPBA, dye, and surfactants. On the basis of the kinetic and spectroscopic data, a mechanistic scheme for the dye degradation reaction and a steady‐state rate equation are proposed. The products resulting from oxidative degradation of the azo dye amaranth have been analyzed by HPLC‐UV‐HRMS. [ABSTRACT FROM AUTHOR]

Background: Human immunodeficiency virus (HIV) infection per se and antiretroviral therapy (ART) both are associated with dyslipidemias, one of the important risk factors in the development of premature atherosclerosis and coronary artery disease. Certain classes of highly active antiretroviral therapy (HAART), especially protease inhibitors, are more frequently associated with dyslipidemia. The objectives of this study were to evaluate and compare lipid profile - total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglyceride in HIV patients before and after starting ART and also to correlate lipid profile and CD4 counts in HIV infection, thus evaluating the feasibility of using lipid profile to monitor the progression of infection in HIV-infected patients as an adjunct to CD4 counts in resource-limited settings. Methods: Paired samples of 100 newly diagnosed HIV patients were taken before and after treatment with HAART. CD4 cell counts and lipid parameters measured and compared using paired 't'-test. Each of the lipid parameter correlated with CD4 cell count. Results: Significant increase was seen in the levels of TC and HDL-C (P < 0.05) with treatment. CD4 cell count also showed a significant increase (P < 0.05) with therapy. HDL-C levels correlated significantly with CD4 cell counts in pretreatment group (r = 0.23, P = 0.020, 95% C.I.). Conclusion: Combination of zidovudine, lamivudine, and nevirapine is associated with significant increase in HDL-C. HDL-C levels are a good indicator of disease severity in HIV-infected patients before starting the therapy. [ABSTRACT FROM AUTHOR]

• A motivational psychology framework is introduced for peer-to-peer energy trading. • A game theoretic design for peer-to-peer energy trading is demonstrated. • An up-to-date literature review of peer-to-peer energy trading schemes is provided. Peer-to-peer trading in energy networks is expected to be exclusively conducted by the prosumers of the network with negligible influence from the grid. This raises the critical question: how can enough prosumers be encouraged to participate in peer-to-peer trading so as to make its operation sustainable and beneficial to the overall electricity network? To this end, this paper proposes how a motivational psychology framework can be used effectively to design peer-to-peer energy trading to increase user participation. To do so, first, the state-of-the-art of peer-to-peer energy trading literature is discussed by following a systematic classification, and gaps in existing studies are identified. Second, a motivation psychology framework is introduced, which consists of a number of motivational models that a prosumer needs to satisfy before being convinced to participate in energy trading. Third, a game-theoretic peer-to-peer energy trading scheme is developed, its relevant properties are studied, and it is shown that the coalition among different prosumers is a stable coalition. Fourth, through numerical case studies, it is shown that the proposed model can reduce carbon emissions by 18.38% and 9.82% in a single day in Summer and Winter respectively compared to a feed-in-tariff scheme. The proposed scheme is also shown to reduce the cost of energy up to 118 ¢ and 87 ¢ per day in Summer and Winter respectively. Finally, how the outcomes of the scheme satisfy all the motivational psychology models is discussed, which subsequently shows its potential to attract users to participate in energy trading. [ABSTRACT FROM AUTHOR]

Spatial and temporal variability of PV generation is a challenge for secure operation of the power systems. Several solutions are already proposed to deal with this issue. Among the proposed solutions, storage technologies (particularly battery) attracted more attention as a promising solution for the application in medium- and large-scale PV plants. While numerous research studies addressed optimal sizing and real-time operation of the storage systems in such applications, there is no study on the battery operation assessment in real-world application based on field data. In this paper, one year of experimental data from a 3.275 MWp PV plant with 600 kW/760 kW h Li-Polymer battery system is examined from different perspectives (e.g., battery energy, power, rate of change of power (RoCoP), and state-of-charge (SOC) ) to draw insights from battery operation within the plant. The field data inherently contains system-wide losses, smoothing effect of the PV plant, and PV inverter operation for reactive power control, which provides a realistic assessment. Furthermore, several operational parameters (such as energy and power during ramp events) are evaluated and modelled using appropriate statistical tools based on experimental data. In addition, a simple super-capacitor sizing study is carried out to reveal the effectiveness of a hybrid energy solution for such applications. Observations and insights drawn from the proposed analyses will help future research on the battery sizing and operation to effectively account for real-world characteristics and requirements. [ABSTRACT FROM AUTHOR]

Fault current limiters are playing an ever more important role in today's power systems and many of their different types have now reached maturity. Owing to the progress in superconducting technology, the superconducting fault current limiter (SFCL) has attracted increasing attentions. To investigate the efficacy of SFCL devices from a system point of view, the fault current limiting impedance is of great importance. This study proposed an improved structure of flux‐lock type of SFCL and compares the current limiting impedance of different layouts. It focuses on the impacts of iron core shape on primary winding inductance. The analyses include simulations based on finite element method carried out in the simulation software ANAlysis SYStem (ANSYS). This study shows that an E–E‐shaped core with an air gap is better than a closed core when being used for an SFCL. It is also found that for an iron core SFCL with fixed size, its rated fault current limiting impedance can be adjusted by changing the cross‐sectional area of the iron core centre leg and the length of the air gap. [ABSTRACT FROM AUTHOR]

In many countries, it is common for medium voltage (MV) and low voltage (LV) to share the same pole and power line corridor, and this has been a general practice for decades. The MV line and the LV line separation distance may be short under some situations; therefore the mutual coupling may become substantial, which can have a significant impact on network voltages. In the literature, such coupling effect is generally ignored, and there is a lack of a detailed model of the coupled MV and LV lines for incorporation into load flow programs. This study develops a model for unbalanced distribution lines considering the mutual coupling between different voltage levels. Then the established model is utilised in a current injection load flow program to analyse the MV/LV coupling impacts on distribution system voltage. [ABSTRACT FROM AUTHOR]

To achieve clean energy targets, more renewable generators – mainly wind and photovoltaic (PV) – are being integrated into electricity networks. However, wind and PV are non-synchronous generators to the grid and they traditionally have neither enough inertia response nor governor support to control major frequency excursions under most situations. Currently in South Australia, the combined generation of wind and rooftop PV has nearly reached the level of average demand with minor support through interconnection import. In such a situation it is likely that there may be fewer synchronous machines online for frequency regulation. Under such a scenario, a contingency could produce a more severe frequency excursion, violating in place frequency standards. Further, many distributed PV systems in South Australia may have a default under-frequency protection setting, which could be higher than the under-frequency load shedding (UFLS) threshold. Hence, a moderate generation/import trip may cause a massive secondary PV trip, which may result in an unacceptably low frequency, triggering further load shedding. This will certainly have an adverse impact on network security. A similar issue of secondary PV trip is not restricted to South Australia and may occur in other regions and countries as well. In this paper, a network which loosely represents the Australian National Electricity Market (NEM) is selected and modified to investigate and analyze network frequency response under high non-synchronous machine penetration. This network contains all necessary models for a comprehensive frequency response study, such as synchronous machine, governor, stabilizer and wind generator. The relevant functions such as load frequency relief, PV tripping and load shedding which are essential for frequency response evaluation are established in the approved and well-accepted platform – PSS®E. The results show that low inertia and secondary PV tripping can become serious issues for network frequency regulation and in some situations they can even cause system oscillation and stability concerns. [ABSTRACT FROM AUTHOR]

A hybrid multi‐terminal HVDC (MTDC) scheme combines line commutated converter and voltage source converter technologies for HVDC transmission system. This study presents a comprehensive design of wide‐area power oscillation damper (POD) controller for the hybrid MTDC system. The process consists of input/output selection and parameter tuning for the POD of the hybrid MTDC based on the linearised black‐box model. The objective is to choose an effective control loop to damp the critical mode, which does not have negative impacts on the other modes in the system. For this purpose, a new index, named relative joint interaction index, is proposed for the input/output selection. Afterward, the parameter of POD is tuned using residue‐based phase compensation technique because of its practical application. Finally, non‐linear simulations are also carried out to verify the effectiveness of the designed POD in different loading conditions. [ABSTRACT FROM AUTHOR]

Background: Dye-binding assays - bromocresol green (BCG) and bromocresol purple (BCP) -are widely used for serum albumin measurement. Differences between the results reported by these assays can have important clinical implications. There are limited studies elucidating the differences between the results of two assays in HIV patients. We aimed to determine whether the choice of assay affects serum albumin measurements in HIV patients. Materials and Methods: Hundred newly diagnosed HIV patients were included in the study. The subjects were followed up for 6-12 months after initiating ART. Hundred HIV-negative healthy controls matched for age and body mass index were taken as controls. Serum albumin and three acute phase proteins (APPs) (Alpha-1 acid glycoprotein, C-reactive protein, ceruloplasmin) were measured. Serum albumin measurement was done by both BCG and BCP dye binding methods. Paired t-test was used to compare the groups. Results: The concentration of APPs reduces with ART indicating reduced inflammation, and is lowest in the control group. The difference in serum albumin concentrations measured by the two dye binding methods reduces with reduction in APPs. The study further indicates that the BCG method gives higher values of serum albumin as compared to BCP method in the presence of other proteins in the sample. Conclusion: The choice of albumin assay affects the serum albumin assessment of HIV patients. We recommend that the BCP assay be used to measure serum albumin in HIV patients, particularly in patients not on ART. [ABSTRACT FROM AUTHOR]

Abstract: Environment friendly policies and emission pricing schemes necessitate the integration of more and more renewable power into electricity grids. However, generation entry and transmission network development in a deregulated market depends on the cost and benefit of a project, where the system/market operator eventually decides the feasibility of investment. In this process, the priorities of market participants are overlooked in some cases. This paper investigates the preferences of market participants in evaluating renewable generation entry to the Australian National Electricity Market (NEM). The priorities of market participants have been investigated through a Multi-Attribute Decision Making (MADM) approach. The TOPSIS (Technique for Order Performance by Similarity to Ideal Solution) algorithm is used to rank the preferences. Optimal Power Flow (OPF) and economic optimization of the Queensland network of the Australian NEM have been simulated in PSS/E and the MATLAB/MatPower software platform. Simulation studies confirm that in the current scenario, gas fired power plants near to the grid will lead in the generation portfolio due to their low lead time, lower investment and dispatchability. Remotely located wind and geothermal power would only be competitive with the existing LRET (Large scale Renewable Energy Target) payments along with very high carbon emission prices. [Copyright &y& Elsevier]

Highlights: [•] Shapley Value approach offers a fair and equitable cost allocation. [•] A case study of the Australian Queensland network is presented. [•] Cost allocation is contentious for remote renewable power transmission. [•] Regulatory policies and planning frameworks need to be updated. [ABSTRACT FROM AUTHOR]

Highlights: [•] PV performance is investigated by utilizing the yearlong recorded data from the PV systems at the University of Queensland. [•] The established theoretical model has good agreement with the field measurement. [•] The validated theoretical model is applied for performance prediction of PV systems in Brisbane, Australia. [ABSTRACT FROM AUTHOR]

This paper proposes an inductively active filtering (IAF) method to comprehensively improve the power quality (PQ) for not only the distribution network (public grid) but also the power-supply system (nonlinear load) connected to the network. At first, a new main-circuit topology for implementing the IAF method is presented, which consists of an inductively filtered transformer and a fully tuned branch controlled by an inverter. Its operating principle and technical features are introduced by comparing with the traditional active filtering method. Based on this, the equivalent circuit is established and by means of mathematical modeling, the unique filtering mechanism of the IAF method is revealed in theory. Further, the control strategy of the FT branch and the impedance coordination for the inductively filtered transformer are designed based on theoretical analysis. A case study is investigated in detail to illustrate the operating characteristics of the IAF method. Both the theoretical and the case studies show that the IAF method can effectively prevent harmonic components from flowing into the primary (grid) winding of the transformer. Since the harmonic components are suppressed near the harmonic source, it is good for the power-supply system and especially good for the converter transformer. Besides, since the harmonic flow is limited to near the harmonic source, the PQ of the public network can be guaranteed completely. [ABSTRACT FROM AUTHOR]

This paper presents a new control scheme for the enhancement of the low-voltage ride-through (LVRT) capability of doubly fed induction generators. The LVRT capability is provided by extending the range of operation of the controlled system to include typical postfault conditions. Controllers are designed simultaneously for both the rotor- and grid-side converters using a linear quadratic output-feedback decentralized control strategy. The nonlinear terms in the power system model are represented in this paper by an uncertain term derived from the Cauchy remainder of the Taylor series expansion. A genetic algorithm is used to calculate the bound on the uncertainty. The robust controller resulting from this design provides acceptable performances to enhance voltage and transient stability margins and thereby to limit the oscillations, the peak value of the rotor current, and the dc-link voltage fluctuations. The performance of the designed controller is demonstrated under different operating conditions by large-disturbance simulations on a test system. [ABSTRACT FROM PUBLISHER]

In distribution power systems line transposition is not a common practice and phase loading levels are always changing. Therefore, perfect balance is never achieved at a distribution level. Non-transposed lines can cause unequal voltage drops between phases and this may be further exacerbated by uneven loads in each phase. Consequently, the voltage magnitude of a certain phase may suffer a severe decrease, breaching the lower voltage limit or unbalanced three-phase voltages at a remote bus may violate the percentage voltage imbalance accepted in the standards. This paper examines the mechanism of causing uneven voltage drops and investigates the impacts of unbalanced line configurations with different phase loading levels on network voltage imbalance. Methodologies are proposed to analyze voltage drops affected by line and load imbalance. Based on these methods, general guidelines are recommended to mitigate the voltage problems, which are useful for network analysis, planning and reconfiguration. [ABSTRACT FROM PUBLISHER]

Dyes in wastewater severely affect the nature and quality of water by inhibiting the sunlight penetration into the stream, which thereby reduces the photosynthesis reaction. This poses a serious environmental threat in many developing countries. Recently, new methods for the treatment of colored dye effluent streams have attracted much attention. The [MnIII(tmpyp)]/H2O2 system (tmpyp= meso-tetrakis(1-methylpyridinium-4-yl)porphyrinato) was now found to degrade various azo dyes with remarkably high efficiency under ambient conditions in aqueous solution at certain pH values. Main products of the catalytic degradation of the dye amaranth by [MnIII(tmpyp)]/H2O2 were analyzed. The reaction mechanism was studied in more detail by using rapid-scan stopped-flow spectrophotometry as a function of pH, [catalyst], [H2O2], [dye], and [surfactants]. Spectral analyses and kinetic data suggested rapid formation of an intermediate [MnIII(tmpyp)(OOH)] (a compound 0-type intermediate), followed by the formation of a relatively stable trans-dioxomanganese(V) porphyrin complex, [MnV(O)2(tmpyp)] (a compound I analog). The one-electron reduction of [MnV(O)2(tmpyp)] to [MnIV(O)(tmpyp)] (a compound II analog) was accelerated greatly by amaranth. On the basis of the kinetic and spectroscopic data, a reaction mechanism of the formation of reactive intermediates [MnIII(tmpyp)(OOH)], [MnV(O)2(tmpyp)], and [MnIV(O)(tmpyp)] was proposed. [ABSTRACT FROM AUTHOR]

Abstract: Investment in transmission for renewable power penetration to the remote grid essentially faces a set of inherent, regulatory, economic and technical challenges. This work investigates these challenges to enhance renewable power integration into the remote grid. This study aims to enhance regulatory policies and associated planning frameworks to be more efficient and justifiable for renewable power integration paradigm. First, a set of leading transmission schemes practiced, or investigated, in different countries are evaluated against the challenges which are obvious for long distance renewable power transmission. Second, a net benefit framework is presented to address the challenging issues of location constrained renewable power penetration into the Queensland network of the Australian grid. The proposed framework incorporates the carbon emission price as an environmental benefit which significantly influences the cost–benefit analysis. This paper discusses the ‘hub approach’ of network integration. The transmission investment cost allocation is addressed here as well. The concepts are verified through the implementation of the proposed framework in four prospective projects of the Queensland network in the Australian national electricity market (NEM). [Copyright &y& Elsevier]

Newly synthesized vanadyl-poly(γ-glutamic acid) complex (VO-γ- PGA) with a VO(O4) coordination mode was found to have potent antidiabetic activity in streptozotocin (STZ)-induced type 1 diabetic mice (STZ-mice), compared with that of a solution containing only vanadyl sulfate, VOSO4. This was the first example of orally active vanadyl complex of γ-PGA for treating STZ-mice. To better define its efficacy, we examined here the effects of VO-γ- PGA treatment in STZ-mice by oral administration at the dose of 10 mgV/kg body mass for a longer period time than our previous study. The improvement in diabetic states in STZ-mice compared with saline-treated nondiabetic normal Std ddY mice. It was found that the elevated blood glucose levels in STZ-mice significantly decreased after 3 days and sustained the normalized blood glucose level around 180-200mg/dL (10-11.1mM) for the last 14 days, which is close to the blood glucose levels 100-200 mg/dL (5.6-11.1 mM) in nondiabetic normal Std ddY mice. The improvement in diabetes was strongly corelated by the improvement in oral glucose tolerance ability, glycosylated hemoglobin (HbA1c) levels and blood pressure, and serum parameters. The present results confirmed that VO-γ-PGA complex is a promising, orally active insulin-mimetic agent to treat type 1 diabetic mice. [ABSTRACT FROM AUTHOR]

Abstract: In order to provide a suitable device that would contain water-soluble drugs, highly water-soluble gadolinium diethylenetriaminopentaacetic acid-loaded chitosan microspheres (CMS-Gd-DTPA) were prepared by the emulsion method using glutaraldehyde as a cross-linker and Span 80 as a surfactant for gadolinium neutron-capture therapy of cancer. The gadolinium content and the mass median diameter of CMS-Gd-DTPA were estimated. The size and morphology of the CMS-Gd-DTPA were strongly influenced by the initial applied weight ratio of Gd-DTPA:chitosan. FTIR spectra showed that the electrostatic interaction between chitosan and Gd-DTPA accelerated the formation of gadolinium-enriched chitosan microspheres. Sufficient amounts of glutaraldehyde and Span 80 were necessary for producing discrete CMS-Gd-DTPA. The CMS-Gd-DTPA having a mass median diameter 11.7μm and 11.6% of gadolinium could be used in Gd-NCT following intratumoral injection. [Copyright &y& Elsevier]

This paper presents the development and application of an analytical method for formalizing the dependence of the behavior of a large power system under fault conditions on the equivalent impedance presented by a single generator. After selecting an appropriate generator model, it is demonstrated that network-wide fault behavior can be expressed as a rational function of the equivalent impedance presented by a single generator under fault conditions. This representation simplifies the identification and depiction of constraints imposed by system configuration on the ability of a generator replacement or augmentation to affect fault behavior. The effectiveness of the proposed method is confirmed by considering the three-phase fault currents produced in a six-bus test system. In addition, the new analytical method is extended to obtain a numerical estimate of the maximum possible change in fault behavior that could result from a generator replacement or augmentation. Overall, the new approach aids in the evaluation of the suitability of generator modification or augmentation schemes. [ABSTRACT FROM AUTHOR]

Abstract: Chitosan, a naturally abundant biopolymer, has widely been studied for metal adsorption from various solutions, but the extension of chitosan as an adsorbent to remove organic substances from water and wastewater has seldom been explored. In this study, the adsorption of an azo dye, trisodium 2-hydroxy-1,1′-azonaphthalene-3,4′,6-trisulfonate (1), from aqueous solution onto the various degrees of deacetylated chitosan has been investigated. Equilibrium studies have been carried out to determine the capacity of chitosan for dye. The experimental data were analyzed using two isotherm correlations, namely, Langmuir and Freundlich equations. The linear correlation coefficients were determined for each isotherm and the Langmuir provided the best fit. The experimental adsorption isotherms were perfectly reproduced in the simulated data obtained from numerical analysis on the basis of the Langmuir model and the isotherm constants. Adsorption of (1) onto the chitosan flakes was found to be strongly depending on degrees of deacetylation in chitosan and temperatures. Significant amounts of (1) were adsorbed by chitosan 8B (higher degree of deacetylated chitosan), but the adsorption capacity was reduced remarkably with increasing solution temperatures. Thermodynamic parameters such as change in free energy , enthalpy , and entropy were also determined. In addition, kinetic study indicated that the adsorption process mechanisms were both transport- and attachment-limited. [Copyright &y& Elsevier]

This paper presents a review of the time-domain polarization measurement techniques for the condition assessment of aged transformer insulation. The polarization process is first described with appropriate dielectric response theories and then commonly used polarization methods are described with special emphasis on the most widely used "return voltage" (rv) measurement. Most recent emphasis has been directed to techniques of determining moisture content of insulation indirectly by measuring rv parameters. The major difficulty still lies with the accurate interpretation of return voltage results. This paper investigates different thoughts regarding the interpretation of rv results for different moisture and ageing conditions. Other time domain polarization measurement techniques and their results are also presented in this paper. [ABSTRACT FROM AUTHOR]

Provides an overview of a dynamic analysis carried out on a modified Nordic test system to determine the impact of the Powerformer on voltage stability. Simulation tools; Purpose of overexcitation limiters; Transformer tap changers and load dynamics; Overexcitation limiter model comparison; Conclusions.

Presents a method to determine the coherent bus groups of a power system with similar reactive reserve basins. Background theory; Assessment methods; Results; Conclusions.

This paper describes the investigation of the insulation condition of a number of power and distribution type transformers of different manufacturing dates and with different operating histories. Return voltage measurements were conducted for these transformers. Effects of moisture and aging on the oilpaper insulation of these transformers were investigated and results are presented in this paper. Moisture in oil samples at known temperature was measured for these transformers. Previously accelerated aging experiments were performed on paper wrapped insulated conductors in different environments over a temperature range of 115 to 145°C. Results from the measurements on transformers are compared with those of the accelerated aged samples and are described in this paper. [ABSTRACT FROM AUTHOR]

• The paper studies peer-to-peer trading based on social cooperation. • A coalition formation game is designed to model the trading between prosumers. • It is shown that the coalitions are stable and optimal. • Motivational psychology is exploited to study the outcome of the scheme. • It is shown that outcomes are prosumer-centric. This paper studies a social cooperation backed peer-to-peer energy trading technique by which prosumers can decide how they can use their batteries opportunistically for participating in the peer-to-peer trading. The objective is to achieve a solution in which the ultimate beneficiaries are the prosumers, i.e., a prosumer-centric solution. To do so, a coalition formation game is designed, which enables a prosumer to compare its benefit of participating in the peer-to-peer trading with and without using its battery and thus, allows the prosumer to form suitable social coalition groups with other similar prosumers in the network for conducting peer-to-peer trading. The properties of the formed coalitions are studied, and it is shown that (1) the coalition structure that stems from the social cooperation between participating prosumers at each time slot is both stable and optimal, and (2) the outcomes of the proposed peer-to-peer trading scheme are prosumer-centric. Case studies are conducted based on real household energy usage and solar generation data to highlight how the proposed scheme can benefit prosumers through exhibiting prosumer-centric properties. [ABSTRACT FROM AUTHOR]

Many solar tracking technologies have been developed with the aim of improving the energy performance of solar PV installations. Among these, single-axis tracking (SAT) systems give good economic prospect for ground-mounted PV plants but experience inevitable power loss when the trackers diverge from the incident solar irradiance during winter. The 1.5-axis tracking (1.5AT) model is developed in recent years to achieve a balance between the benefits and shortcomings of the SAT and dual-axis tracking (DAT) systems. Despite the anticipated superiority of the 1.5AT, there is a lack of literature on the methodology to analytically study the potential and feasibility of the 1.5AT model, especially from a global perspective. In this paper, a comprehensive feasibility study has been conducted to evaluate the energy performance and shading analysis of the 1.5AT model. The developed methodology serves as a general benchmark to explore the prospects of the 1.5AT model at different geographical locations and seasons. This encourages further research and deployment of the 1.5AT model as a potential alternative to improve the return of investment for various PV system stakeholders. [ABSTRACT FROM AUTHOR]

This article presents a new approach for classification and localization of voltage sags triggered by symmetrical and unsymmetrical faults in electricity networks. The proposed method utilizes five unique parameters of three-dimensional (3-D) polarization ellipse (PE) obtained from the mapping of three-phase voltage signals in 3-D coordinates. The decision boundaries, which are set by the parametric equations exploiting the five ellipse parameters, namely, elevation, azimuth, tilt angles, semi-major axis, and semi-minor axis, are used to classify the fault-initiated sags. The localization of faults is conducted from the parametric equations demonstrating the variation of ellipse parameters with respect to distance from the fault-location. These parametric equations would be helpful to make decision faster and thereby, eliminate the uncertainty in decision-making process. The applicability of the proposed method is tested and validated using real data measured by DOE/EPRI, the recorded waveforms of IEEE 1159.2 Working Group, and the data extracted from the simulation of faults at several feeders of IEEE 14-bus test system using RSCAD and Real Time Digital Simulator (RTDS) platform. [ABSTRACT FROM AUTHOR]

• An approach to automatically detect, locate and identify faults type in PV systems. • The approach can detect and differentiate between all types of line to line faults. • Fault type detection and identification is based on fault signals called residuals. • Fault location is estimated from relationships between of locations and currents. • The proposed approach is experimentally validated on different solar array sizes. Due to exponential growth of large-scale PV plants, automatic approaches for PV system protection are gaining prodigious importance. Even with the use of standard protection devices, faults in PV arrays may remain undetected. To address such an important issue, this paper focuses on string level monitoring to develop the functionality of automatic fault detection, location and fault type identification. The fault detection is achieved through the generation of fault indicator signals called residuals and comparison with a pre-set threshold. The automatic identification of fault type is achieved by the development of a procedure reliant on the variations in the string current profiles relative to the type of fault. Finally, the location of faults is estimated through the combination of analytical and regression expressions reliant on fault type, irradiance levels and string current measurements. Various line-line fault cases are tested and verified using the proposed method through simulations and experiments. The proposed method is experimentally evaluated for multiple fault scenarios on an experimental setup located within an existing solar farm to emulate conditions akin to real world solar farms. [ABSTRACT FROM AUTHOR]

Synchronous generators are operating for less time than before or being decommissioned in the National Electricity Market (NEM) of Australia, due to the proliferation of asynchronous wind and solar generation. Sub-networks of the NEM will face inertia shortages in the near future. This paper develops a formulation of zonal inertia constrained generator dispatch for power systems with a diversified generator portfolio including synchronous generators, synchronous condensers, inverter-interfaced generators and energy storages. Zonal inertia constraints are formulated in unit commitment and optimal power flow to limit the rate of change of frequency (RoCoF) in the event of network separation. Load frequency relief is also considered to reduce the ramp rate requirement of primary reserve. The proposed formulation can reduce the average cost of primary reserve and maintain zonal inertia adequacy to constrain RoCoF in case of the trip of the interconnector(s). [ABSTRACT FROM AUTHOR]

• A fault detection and location approach to detect intra-string faults. • Fault detection is based on generation of fault indicator signals called residuals. • Fault location is modelled in terms of string current and irradiance measurements. • The approach is shown to be applicable for any array configuration. • The proposed approach is experimentally validated on different solar array sizes. The task of fault detection and diagnosis in large-scale photovoltaic (PV) plants is expected to be a major challenge as more and more plants with increasingly large capacities continue to come into existence. To maintain safety, reliability, and productivity of large-scale PV plants it is essential to develop approaches that allow automatic detection and location of any mal-operation among thousands of PV modules. This paper proposes an approach to detect PV plant faults through the generation of fault indicator signals called 'residuals' for each string and the comparison of residuals with a threshold value. Furthermore, a regression-based approach is proposed to estimate fault location as a function of fault current and irradiance level measurements. The proposed approach is demonstrated by specifically focusing on intra-string line-line faults. Various line-line fault case studies are verified through simulations and validated on an experimental setup in a solar PV plant. Initially the approach is developed for a fixed size PV array, but subsequently extensions of the proposed approach to any array size are developed and presented. The generalisation potential of the approach is demonstrated through successful validation on multiple PV array configurations. [ABSTRACT FROM AUTHOR]

The measurement of water inside a transformer is essential to maintain its reliable operation, as the water content can increase as the transformer ages. This measurement is frequently performed by a utility as a part of its periodic maintenance activities. In this paper, the application of optical fiber sensors as an online method to measure water content of paper inside an operating transformer is presented. There are several advantages of using these sensors, including their size, lightweight, flexibility, multiplexing, no-electromagnetic interference, etc. A unique benefit of fiber optic technology is that sensors can be embedded into the winding structure and operate in areas of high electric field strength. For this work, fiber optic water and temperature sensors are investigated by comparing their measurements to a commercial water activity probe immersed in oil. The study found that the determination of water content by fiber optic sensors compared closely with other techniques, which lead to the conclusion that they can be an effective technology for water measurement in an operational transformer. [ABSTRACT FROM AUTHOR]

The power transformer is a key element in a power system and its condition needs to be monitored and evaluated. However, subject to electrical, thermal, and mechanical stresses, the condition of a power transformer can eventually deteriorate causing the loss of the transformer's useful life. Utilizing various condition monitoring data of the transformer, this paper applies a state-space model method to the transformer's remaining useful life estimation. In the state-space model, a state dynamic equation considering the transformer aging mechanism is developed. Three measurement equations using different types of condition monitoring data are established. To solve the nonlinear state-space model, a particle filtering approach is applied. The posterior probability density function of the state variable obtained from the particle filtering is used to determine the transformer's remaining useful life. A number of case studies are carried out to demonstrate the applicability of the proposed method. [ABSTRACT FROM AUTHOR]

Vibro-acoustic measurement on a transformer's on-load tap changer (OLTC) can provide indications on its mechanical condition. Recently, a joint vibro-acoustic and arcing measurement system has been proposed, which can correlate the vibro-acoustic signal to mechanical events of OLTC's operation. However, there are still considerable difficulties in extracting useful information from both vibro-acoustic signal and arcing signal in a synchronized manner without any distortions in the extracted signals. In this paper, Savitzky–Golay filter is introduced to process the signals acquired from a joint vibro-acoustic and arcing measurement system installed on in-service OLTCs. It proves that the Savitzky–Golay filter can process both vibro-acoustic and arcing signals induced by OLTC, extract essential information without any time delay from both types of signals, and retrieve voltage phase information from the arcing signal. The methodologies developed in this paper can improve the visibility of OLTC's mechanical operation for an effective online condition monitoring. [ABSTRACT FROM PUBLISHER]

With the rapid development of photovoltaic (PV) technology, more utility-scale PV systems are being integrated into rural areas where abundant and low-cost land is available. In these areas, step-voltage regulators (SVRs) with an open-delta configuration are widely used for voltage regulation. However, since SVRs were initially designed for tackling slow and smooth load variations, frequent PV output fluctuations can cause excessive tap changes. Moreover, rural communication facilities are normally expensive and underdeveloped, so only limited parameters are recorded with low resolution and reliability. Thus, much needed tap information cannot be properly monitored in a cost-effective way. In contrast, a downstream load center or utility-scale PV site is commonly well equipped with modern sensors and data acquisition systems, which provide the possibility for tap evaluation. Therefore, this paper proposes a new remote tap position estimation approach to accurately assess the upstream tap positions of open-delta SVRs from downstream measurements. Furthermore, the proposed approach is firmly validated through field testing under the support of the local utility and PV plant owner. This novel method not only enables reliable tap position monitoring with high precision for utilities to research PV–SVR interaction, but also provides valuable information to PV owners for correctly analyzing downstream voltage performance. [ABSTRACT FROM AUTHOR]

This study develops a long-term integrated planning approach to electricity and gas aiming at economically optimizing the 2030's investments of both networks while considering new policies towards future clean energy. A static stochastic cost minimization model is formulated, which takes into account the short-term uncertainties of renewable power, i.e. wind and utility-scale solar photovoltaic (PV) as well as the long-term uncertainties of load growth and gas price. The equivalent networks of both electricity and gas are driven to accurately capture their existing supplies and transmission networks. In addition, the integrated planning model allows determining the location of new power plants and gas supply facilities with their optimized capacities, as well as new transmission lines and pipelines. An extension of the proposed scheme is considered to accommodate higher penetrations of renewable energy and assess their impacts on both systems. The proposed model is applied to the state of Queensland in Australia, which is a prime example of a region actively integrating electricity and gas. [ABSTRACT FROM AUTHOR]

The installed capacity of wind generation and photovoltaics (PV) in many countries is going to dominate generation fleets in a bid to meet growing renewable energy targets. Synchronous inertia has never been problematic as there was more available than needed, but it is being significantly reduced due to the increasing integration of nonsynchronous renewable generation. When the low bidding priced generation of wind and PV becomes considerably large, conventional economic dispatch algorithms can result in less online synchronous inertia and put power system security at risk. However, the compromise of power system security due to synchronous inertia shortage is not well studied in the literature. This paper develops a synchronous inertia constrained economic dispatch algorithm to satisfy the minimum required synchronous inertia of frequency control. Synchronous condensers and wind reserve are economically allocated to alleviate any shortage of synchronous inertia and frequency control ancillary services (FCAS). A Gaussian particle swarm optimization algorithm is introduced to simultaneously co-optimize the dispatch of synchronous generators and their FCAS, wind reserve, and synchronous condensers. [ABSTRACT FROM AUTHOR]

Degradation of photovoltaic (PV) modules is inevitable regardless of the size of a PV plant. While it is understood that degradation leads to a reduction in power generation, the effects of module degradation on PV plant protection system remains somewhat unclear. Considering that most of the PV plant protection system settings are based on modules in good conditions without degradation, it is imperative to evaluate the effect of module degradation on fault detectability by conventional protection infrastructure to ensure safety and reliability of PV plants. The purpose of this paper is to investigate the relationship between the levels of module degradation and PV plant faults including fault current levels, fault locations and types of faults. An experimental setup comprising of 16 modules of varying degradation levels is used to generate multiple short circuit fault scenarios. The results indicate that degradation results in a decrease in string current, which may lead to an increased likelihood of fault undetectability using conventional protection settings. [ABSTRACT FROM AUTHOR]

Any mismatch between load and generation (due to a generator or an interconnection trip) is intended to be balanced and stabilized by contingency reserve, which is also known as contingency Frequency Control Ancillary Services (FCAS) requirement. Load Frequency Relief (LFR), which represents the effect of frequency dependent loads on power system frequency excursion, is crucial for correctly evaluating contingency reserve requirement during generation dispatch to ensure an adequate frequency response. Over estimation of LFR can be accountable for less planned reserve during an economic dispatch that may cause undesirable frequency performance. On the other hand, under estimation of LFR can result in an excessive reserve and hence could unnecessarily increase system operational cost. Conventionally, LFR is considered as a fixed quantity during the evaluation of FCAS requirement. However, recent experience in the Australian power grid suggests that such an assumption may lead to an inaccurate outcome. To explore the above issue, this research investigates the LFR using field measurement data, which were captured at different locations of the southern states of Australia (e.g., Tasmania and Victoria). An approach is developed to identify the predominating factors affecting the LFR and subsequently a technique is proposed to appropriately determine contingency FCAS requirement. [ABSTRACT FROM PUBLISHER]

Short circuit (SC) strength of a power transformer is influenced by its winding clamping pressure. The required level of clamping pressure is selected at the design stage based on the maximum allowable SC current level of the transformer. Progressive loss of clamping pressure is a common problem in power transformers. Shrinkage and fading of the stiffness of solid insulation due to thermal degradation are the most common causes of this problem. It has also been identified that changes in the moisture content and repetitive compression cycles on pressboard during high current faults tend to change the winding clamping pressure. This study aims to investigate the effects of moisture and compression cycles on winding clamping pressure through a set of laboratory experiments and finite element analyses. Thickness change and compressive stress-strain curves of pressboard were measured under different moisture conditions. The results were then used to calculate changes in winding geometry and clamping pressure of a 100 kVA three phase, disc type transformer winding. [ABSTRACT FROM PUBLISHER]

A letter to the editor is presented in response to the article "Clinicopathological Profile of Wilms' Tumor in Children" by M. Majumder et al published in Vol. 32, No. 1 Journal 2014 issue.

Vibration measurement has been adopted in some utilities in Australia, Canada, and several European countries for online condition monitoring of the power transformer's onload tap changer (OLTC). By comparing measured vibration signals at different stages, it might be possible to assess changes of OLTC's condition. However, there are still considerable difficulties in correlating vibration signals to the events of OLTC operation, which may impair the capability of vibration measurement for OLTC condition monitoring. Therefore, arcing measurement is proposed in this paper to complement the vibration measurement. Arcing is provoked when the OLTC switching contact closes at a fixed tap position and can lead to electromagnetic signals flowing through transformer windings, finally reaching earth. The arcing measurement is achieved by using a high-frequency current transducer (HFCT) clamping on the transformer's grounding cable. The joint vibration and arcing measurement can provide a better means for interpreting events involved in OLTC operation and facilitating improved OLTC condition monitoring. Since HFCT measured arcing signals can be coupled with noise, a probabilistic wavelet transform is thus employed in this paper to extract arcing signals from noise. Field measurements on two different types of OLTCs are performed using the joint vibration and arcing measurement system to validate the proposed methodology. [ABSTRACT FROM PUBLISHER]

Power system security concerns due to significant wind generation could be twofold: first, the frequency response and second, the short‐circuit performance. Continuous development of wind energy may cause economic replacement and retirement of existing synchronous generators. Modern wind turbine generators do not inherently offer inertia and governor response after a disturbance, which may result in declining frequency response behaviour. Besides, they have limited fault current contribution, which may cause unacceptable short‐circuit ratio at the grid connection point of those wind power plants. Traditionally, frequency response and short‐circuit performance are individually improved. However, both of them are concurrently affected by high wind penetration. Hence, a common approach to simultaneously enhance both indices is essential. Therefore, this study introduces an idea of operating some of the retired synchronous generators in the synchronous condenser mode, which is termed as 'post‐retirement scheme (PRS)'. Such a second use of the retired synchronous generators can jointly upgrade frequency response and short‐circuit strength during high wind generation. This study also proposes a methodology to evaluate when and how much PRS should be deployed for ensuring an adequate security performance in a wind dominated power system. [ABSTRACT FROM AUTHOR]

Though synthetic test methods are widely used for testing high-power circuit breakers (CBs), synthetic testing has not been reported in the literature as being extended to the testing of medium-voltage (MV) load break switches (LBS). This paper investigates the possibility of type testing of MV LBS using synthetic test procedures. The transient recovery voltage (TRV) required is calculated from both IEC and IEEE standards and it is shown that the IEC TRV specification results in a more severe TRV. It is found that testing with a basic Weil circuit requires two-part testing. In one test, a low-amplitude TRV with a fast rate of rise stresses the early region associated with thermal failure. In the other test, a higher-amplitude slowly rising TRV stresses the later dielectric region. However, the two-part test using the unmodified Weil circuit is shown to cause significant TRV overstressing. Insertion of a precharged capacitor and additional damping resistors into the Weil circuit at critical times using triggered spark gaps are found to be effective to reduce overstressing. Simulation results show that it is possible to use a modified synthetic test circuit to test LBS with voltage ratings of up to 38 kV and load currents of 800 A. [ABSTRACT FROM PUBLISHER]

This study investigates the influence of moisture, temperature and diverse oil properties on the frequency domain response of pressboard insulation samples, which are impregnated with four different insulating liquids including two commercially available natural esters, one synthetic ester and mineral oil. Measurements are performed over a wide frequency range from 0.1 mHz to 1 kHz at variable moisture contents and temperatures (35, 55 and 75°C). It has been found that dielectric response is extremely sensitive to moisture content regardless of the type of impregnated liquid. Furthermore, dielectric response behaviour of ester impregnated pressboard insulation is qualitatively resembles to that of mineral oil impregnated pressboard which contains two distinct relaxation processes including Quasi-DC (q-dc) conduction features at low frequencies, and loss peak behaviour at mid frequency range. This paper proposes that the loss peak arises due to cooperative microscopic motion in water cellulose mixed phase dipole clusters together with the microscopic level interfacial polarization occurring at the interface of oil filled cavities. It is also discussed the q-dc process in pressboard insulation due to the charge transport between water and oil cavity based charge clusters through a percolation network of water molecules and hydroxyl groups along the cellulose fiber wall. In order to provide better understanding on charge transport and polarization phenomena in oil impregnated pressboard insulation, this paper also proposes an equivalent circuit, which is mainly derived based on Dissado- Hill (DH) cluster framework theory. Furthermore, this study has used activation energy to characterize the temperature dependent dielectric response of pressboard impregnated in mineral oil, natural esters and synthetic esters. [ABSTRACT FROM AUTHOR]

• A semi-analytical approach is developed to obtain the BESS power reserve for FFR. • The local minimum power reserve is derived to avoid UFLS under a large contingency. • The proposed method bridges the gap of the trial-and-error approaches. • The effectiveness of the proposed method is validated with an actual network model. • The methodology will advance grid services estimation and battery management. The large-scale renewable energy integration faces a challenge of frequency stability due to low inertia in weak power grids. One solution to mitigate this issue is via the fast frequency response service provided by battery storage systems so that the overall grid response during a large power outage can be improved. The battery power reserve is crucial to ensure the frequency ancillary services provision. However, grid operators currently investigate the contingency reserve of batteries through inefficient processes, such as extensive simulations or trial-and-error methods. Therefore, this paper proposes a semi-analytical methodology to quantitively determine the minimum required battery power reserve for preventing under-frequency load shedding when a severe generation trip occurs. This minimum reserve is derived from the time-variant kinetic energy of a given dispatch case. Case study results of the Mexican network demonstrate that the calculated battery power reserve can provide a cost-effective fast frequency response for a real islanded network. The research outcomes offer valuable insights for battery management and grid ancillary services requirement estimation in the transition to power networks dominated by converter-interfaced renewable energy resources. [ABSTRACT FROM AUTHOR]

Partial discharge inception voltage (PDIV) at different frequencies is of great interest for PD tests conducted at nonpower frequency. However, in the existing literature, there is no agreement on PDIV characteristics with respect to frequency. There is a lack of comprehensive analysis of frequency-dependent PDIV characteristics either. In this article, the PDIV of a cylindrical void at different frequencies (from 0.5 to 300 Hz) is investigated from the perspective of the first PD time lag. First, an appropriate time interval between consecutive measurements is experimentally determined. Then, PDIV measurements at different frequencies are conducted by increasing voltage at a fixed ramp rate. Furthermore, the PDIVs defined by peak voltage and instantaneous voltage are compared. After that, a bipolar square wave is applied to measure the first PD time lag. Finally, based on the first PD time-lag distribution with respect to voltage at different frequencies, the cumulative probability of the first PD under sinusoidal voltage is computed and analyzed. The results suggest that the first PD time lag has a significant influence on the measured PDIV at frequencies above 10 Hz. This is because the mean time lag is nearly half the time period of half voltage cycle at low voltages. Thus, high voltages (HVs) are needed to obtain a high probability of the first PD, i.e., a large measured PDIV. [ABSTRACT FROM AUTHOR]

Cellulose based insulation materials and mineral oils have widely been used in liquid filled transformers. Environmental and fire-safety concerns have accelerated the use of Natural Esters (NE) as a sustainable alternative to mineral oil. There is a rapid growth of their application for distribution level transformers. To ensure a safe and long-term operation of the vegetable oil filled transformers, it is necessary to clarify the knowledge gaps with respect to the ageing of vegetable oil impregnated cellulose and insulation diagnostic methods. The condition monitoring of mineral oil filled transformers has been well characterised, due to the numerous laboratory and field studies conducted during the past several decades. The application of these available condition monitoring techniques for NE filled transformers is yet to be validated as the use of NE for power transformers is in the evaluation stage. In this paper the performance of NE as insulation in transformers by evaluating the ageing of NE impregnated cellulose pressboard is presented. For this purpose, an accelerated ageing experiment has been carried out in sealed tubes at 120 °C. The ageing of oil impregnated pressboard has been characterised by decrease in the degree of polymerisation (DP) of pressboard, and the formation of both 2-furfuraldehyde and dissolved carbon dioxide (CO2) in the oil. The structural changes of cellulose have been supported by Fourier Transform Infrared (FTIR) spectra. Moreover, the results have been compared with cellulose insulation samples aged under similar conditions in conventional mineral oil. Acidity value, dissipation factor and viscosity measurements have been used to compare the stability of NE in a transformer operating environment to mineral oil. [ABSTRACT FROM PUBLISHER]

Renewable generations are growing fast and they are becoming the major generation technology in power systems. Amongst all renewables, wind and solar resources have the highest growth rate. However, fluctuation and uncertainty of these sources are the main barriers in their utilization and can affect reliability of power system. Therefore, these generators must be treated differently in adequacy studies and their reliability contribution should be evaluated. South Australia (SA) accounts for more than half of Australia's wind share and its solar capacity is rapidly increasing as well. Thus, not only the reliability benefit of wind is required to be investigated in this power system, but also the contribution of solar energy and its impacts should be analysed as well. The reliability benefit of wind and PV has been studied in the literature, but there is a need to evaluate their combined contribution in reality and investigate the influence of their correlations. Therefore, this paper evaluates the reliability contribution of wind and solar power in South Australia and the impact of solar energy on wind load carrying capability. State sampling Monte Carlo technique is utilized for reliability assessment and Fuzzy C-means clustering method is employed to create a multistep load model. [ABSTRACT FROM AUTHOR]