Search

This paper proposes an integrated method for the accurate and fair cost allocation of the transmission system among the users (generators and loads) of the network. It mitigates the existing research gaps and implementation issues in the marginal participation approach for network cost allocation. Major challenges in the marginal participation approach are 1) fair selection of economic slack busses 2) inaccuracy due to use of DC power flow 3) treatment of the counter flows and 4) enforcement of cost-causality. While the prior art has addressed the sub-problems individually, an integrated approach has been missing. This work fills this research gap. Besides, it for the first time introduces the use of linearized AC power flow for calculating the marginal flows. This provides a major improvement over the DC power flow model as nominal voltage and reactive power variables can be modeled without compromising linearity. Economic slack bus selection by min-max fairness approach, modelling of counter flows without resulting in negative cost-shares (payoffs), enhancement of cost-causality by segregating usage cost, reliability cost, and residual costs are other salient contributions of the proposed work. These features result in a rigorously fair, accurate, and yet tractable method computationally. Case-studies on many systems including the IEEE-118 bus system demonstrate the claims made. [ABSTRACT FROM AUTHOR]

Ni-Mo low alloy steel exhibits an admirable amalgamation of high strength and toughness at subzero temperature and show resistance to brittle fracture with good weldability. This steel has been established to fulfill the needs of specific applications, such as the construction of ships and submarines. To develop a companionable wire for welding of Ni-Mo low alloy steel, the amount of the alloying elements in a wire is increased to toughen of weld metal, the wire itself has high strength so that the wire is hardened at the wire drawing, making the wire production difficult. In order to avoid the problems related to the solid wires, various flux cored wires have been developed. In this work, the effect of flux basicity index and heat input on chemical composition, oxygen-nitrogen analysis, mechanical properties and microstructure of Ni-Mo low alloy steel welded by SAW welding using flux cored wires are presented along with the effect of flux cored wire and basicity index on deposition rate. [ABSTRACT FROM AUTHOR]

We present an empirical analysis to show that combination of short term load forecasts leads to better accuracy. We also discuss other aspects of combination, i.e., distribution of weights, effect of variation in the historical window and distribution of forecast errors. The distribution of forecast errors is analyzed in order to get a robust forecast. We define a robust forecaster as one which has consistency in forecast accuracy, lesser shocks (outliers) and lower standard deviation in the distribution of forecast errors. We propose a composite ranking (CRank) scheme based on a composite score which considers three performance measures-standard deviation, kurtosis of distribution of forecast errors and accuracy of forecasts. The CRank helps in identification of a robust forecasts given a choice of individual and combined forecaster. The empirical analysis has been done with the real life data sets of two distribution companies in India. [ABSTRACT FROM AUTHOR]

Distance relays are the workhorses of transmission-line protection systems. But those close to the electrical center will pickup even during transient instability. To identify them, we introduce a new coordinate system with normalized minimum magnitude of positive-sequence voltage on the line (\mathrmV{\mathrm{min}\mathrm{pu}}) as the y-coordinate and angular separation of positive-sequence voltage phasors at line terminals (\delta \text{SR}) as the x-coordinate. We show that in the \delta \text{SR}-{\mathrm{V}}{\mathrm{min}\mathrm{pu}} plane, the electrical center has a strong separation from a three-phase fault and stable disturbances. Subsequently, we propose a combined out-of-step prediction and relay blocking scheme. It uses line-end phasor measurement unit inputs for detecting vulnerable relays and blocking their zone 1 trip for a limited time interval before ingression into zone 1. We also show that it is possible to detect a line fault during the block state and consequently rescind the block decision. Extension of the proposed scheme to zone 2 and zone 3 is also described. Simulations considering noisy data and round robin delays demonstrate efficacy of the proposal. [ABSTRACT FROM PUBLISHER]

Objective: To study the gender differences in perceived social support and life events in patients with depression. Methods: A total of 118 patients aged 18 to 60 years, with depressive disorder according to the DSM- IV-TR. were evaluated using the Multidimensional Scale of Perceived Social Support and Presumptive Stressful Life Events Scale. Results: The perceived social support score was significantly higher in males than females (p < 0.001). Males perceived significantly higher social support from friends than females (p < 0.001), whereas support from significant others was higher in females. There was a higher mean number of total life events as well as specific type of life events in males that became apparent after controlling for education (p < 0.05). Financial loss or problems was the most commonly reported life event in both males and females. Work-related problems were more commonly reported by males, whereas family and marital conflict were more frequently reported by females. Conclusion: Perceived social support and stressful life events were higher in males with depression than females. [ABSTRACT FROM AUTHOR]

We consider the problem of allocating the cost of a transmission system among load and generator entities. It is a known instance of the classical cooperative game theoretic problem. To solve this problem is a formidable task, as we are dealing with a combinatorial game with transferable utilities. This is an NP hard problem. Therefore, it suffers from the curse of dimensionality. Marginal pricing is a pragmatic alternative to solve this problem since both Kirchhoff current law and voltage law are strictly adhered to. However, the generic complexity of cooperative game theoretic problems cannot be just wished away. It now manifests as the difficulty in choosing an economic slack bus, which may even be dispersed. We propose the application of min-max fairness policy to solve this problem and give an algorithm which will run in polynomial time. During network cost allocation, min-max fairness policy minimizes the maximum regret among participating entities at each step. Maximum regret is measured in terms of price, and lexicographic application of this principle leads to a fair and unique equilibrium price vector. Results on a large network demonstrate fairness as well as tractability of the proposed approach. [ABSTRACT FROM PUBLISHER]

The synthesis of various amide and ester derivatives of naphthopyrone-2-carboxylic acid has been carried out by reaction of 1-naphthol with dimethyl acetylenedicarboxylate, which gave a mixture of E and Z isomers of naphthoxy diester. The diester on with KOH gave corresponding diacid, which was a mixture of E and Z isomers. The E and Z isomers were difficult to separate, which were subjected to in sulfuric acid to get cyclized naphthopyrone carboxylic acid. This acid is converted into titled compounds. [ABSTRACT FROM AUTHOR]

The effect of processing parameters on the mechanical and metallurgical properties of dissimilar joints of AA6082-AA6061 produced by friction stir welding was analysed in this study. Different FSW samples were produced by varying the welding speeds of the tool as 50 and 62 mm/min and by varying the alloy positioned on the advancing side of the tool. In all the experiments the rotating speed is fixed at 1600rpm. All the welds were produced perpendicularly to the rolling direction for both the alloys. Microhardness (HV) and tensile tests performed at room temperature were used to evaluate the mechanical properties of the joints. In order to analyse the microstructural evolution of the material, the weld's cross-sections were observed optically and SEM observations were made of the fracture surfaces. The corrosion tests of base alloy and welded joints were carried out in 3.5%NaCl solution at a room temperature. Corrosion current and potential were determined using potentiostatic polarization measurements. It was found that the corrosion rates of welded joints were higher than that of base alloy. [ABSTRACT FROM AUTHOR]

1-Methylchromeno[3,4- b]pyrrol-4(3H)-one and 1-phenylchromeno[3,4- b]pyrrol-4(3H)-one derivatives have been synthesized by cyclization of amides obtained by condensing α-halo ketones with 3-amino-chromenones, which show cytotoxic activity against lung, colon, and breast cancer cell lines. [ABSTRACT FROM AUTHOR]

Power flow tracing has been suggested as an approach for evaluating 1) transmission system usage (TSU) cost and 2) loss (MW) cost for generator and load entities in the system. Recently, optimal power flow tracing methods have been proposed to "explicitly" model fairness constraints in the tracing framework. This paper, further, strengthens the tracing-compliant min-max fair cost allocation approach. The min-max model proposed in this paper is robust. It addresses concerns like scalability, numerical stability and termination in a finite number of steps while searching the optimal solution. We also propose a methodology to model DISCOMs and GENCOs as coalition within min-max framework. Case studies on an all India network of 1699 nodes and comparison with average participation and marginal participation methods bring out the better conflict resolution feature of the proposed approach. A method to model HVDC lines within the marginal participation scheme is also proposed. Quantitative and qualitative comparison of various TSU cost allocation methods on such a large system is another noteworthy contribution of the paper. [ABSTRACT FROM AUTHOR]

We propose a new approach to current differential protection of transmission lines. In this approach, we transform the instantaneous line current(s) by using a moving window averaging technique. If the time span of moving window is equal to one-cycle time, then the steady-state value of the transformed current is zero for a periodic signal which is composed of fundamental and harmonic frequencies. Signal distortions (e.g., a fault) cause the transformed currents to deviate from the nominal zero value. This permits the development of a sensitive, secure, fast, and yet simple current differential protection scheme. The scheme can be applied in toto to series-compensated transmission lines. Results on a four-machine ten-bus system and comparative evaluation with state-of-the-art methods brings out promise of the proposed method. [ABSTRACT FROM AUTHOR]

Throughout the history of power system protection, researchers have strived to increase sensitivity and speed of apparatus protection systems without compromising security. With the significant technological advances in wide-area measurement systems, for transmission system protection, current differential protection scheme outscores alternatives like overcurrent and distance protection schemes. Therefore, in this paper, we address this challenge by proposing a methodology for adaptive control of the restraining region in a current differential plane. First an error analysis of conventional phasor approach for current differential protection is provided using the concept of dynamic phasor. Subsequently, we extend the methodology for protection of series compensated transmission lines. Finally, we also evaluate the speed versus accuracy conflict using phasorlets. Electromagnetic Transient Program simulations are used to substantiate the claims. The results demonstrate the utility of the proposed approach. [ABSTRACT FROM AUTHOR]

The present investigation reports the synthesis of new furobenzisoxazole derivatives. Posner reaction of hydroxyfurocoumarin has been studied, wherein the two reaction products are identified as 5-methylfuro[2′,3′:4,5]benzo[1,2- d]isoxazol-3-yl)acetic acid and 1-(6-hydroxy-3-methylbenzofuran-5-yl)ethanone oxime, depending on the conditions used. 1,3,4-Oxadiazole, 2-mercapto-1,3,4-oxadiazole and thiazolidinone derivatives of furobenzisoxazole were synthesized from hydrazide. [ABSTRACT FROM AUTHOR]

Conventionally, transmission fixed cost allocation is carried out on postage stamp basis. Amongst various other ways of solving the problem, the cost allocation under the "usage-based" domain has also been suggested, namely, based on proportionate tracing and recently, by optimization based real power tracing. Changing the cost allocation regime from postage stamp basis to usage-based methods, though technically sound, can pose fairness issue. The fairness criteria in its simplest form would allocate cost in equitable manner oh per unit basis while meeting the constraints. The optimization-based tracing provides room for defining an objective, leading to tracing compliant postage stamp method, that strikes a balance in allocation between conventional postage stamp and proportionate tracing-based methods. In this paper, we address this complex cost sharing problem by suggesting a min-max fairness algorithm, using optimization-based real power tracing. The min-max algorithm achieves fairness by equalizing allocations within constrained space and reaching an equilibrium where further balancing cannot be achieved. We show that computing min-max fair solution simply corresponds to solving a sequence of sparse LP problems for real power tracing. The algorithm satisfies the property of aggregate invariancy. Results on actual data of central transmission utility of Western Regional Grid of India, as well as IEEE 30-bus system, validate the claims. The results are compared with the tracing compliant postage stamp method. [ABSTRACT FROM AUTHOR]

Megawatt (MW) power flow tracing can assess the extent of network usage by the participants that can be effectively used for multiple objectives like transmission pricing, loss allocation, etc. MW power tracing, a post-facto analysis of power flow solution, is amenable to multiple solutions. This implies multiplicity of solution space of transmission cost and loss allocation problems. The conventional tracing methods enforce a ‘proportionate sharing rule’ to calculate the shares. These shares are sensitive to quantity and distance as against the postage stamp method, which is immune to distance. Any of these methods will result in penalizing a set of constituents, which raises a fairness issue. This is evident from the experiences of developing countries like India. In this paper, a new paradigm is suggested that attempts to capture the best of the two methodologies by exploring multiplicity of the solution space of the tracing problem, within the given constraints. We show that the tracing problem can be formulated as a linear constrained optimization problem. We propose a tracing compliant modified postage stamp allocation method that computes a traceable solution that minimizes overall deviation from the postage stamp allocation. Results on actual data of central transmission utility of Western Regional Grid of India demonstrate the claims. [ABSTRACT FROM AUTHOR]

In India, apart from state owned generators, a central sector power pool has been created consisting of central sector power stations. The Central Transmission Utility (CTU) has built an EHV network to transfer this power to the constituents of the regional network. To recover the costs incurred, the CTU levies the Transmission Service Charges (TSC) over the constituents. The constituents are billed for network usage charges which are proportional to their allocated share in the central sector power generation. An ideal pricing mechanism would have been to find out the usage of the network by the constituents and charge accordingly. In this paper, a real power tracing based method for recovery of Transmission Service Charge (TSC) from the constituents of Western regional grid in India is proposed. The method uses proportionality based real power tracing to find out the network usage by various constituents. Loss allocation on EHV network to the various constituents is also done. Actual data of power flows over the EHV network of Western regional grid for one day is considered. [ABSTRACT FROM AUTHOR]

Postfault rotor angle oscillations lead to power swings. Both unstable and stable swings can induce distance relay tripping. For unstable swings, a new computational procedure to locate all of the electrical centers is developed. It simplifies the work associated with visual screening of all the R-X plots. For stable swings, a generic three-tier hierarchy of stability-related norms defined by branch norm, fault norm, and system norm is proposed. Ranking by branch norm leads to ranking of power swings. Ranking by fault norm leads to ranking of faults or contingencies. Magnitude and rate of change of system norm can be used to detect an out-of-step condition. Results on a ten-machine system and a utility system with detailed models are also presented. [ABSTRACT FROM AUTHOR]

Presents design of generic Linear System Solver for power system analysis. Description of the Linear System Solver with complex matrices; Implementation of associative array; Results.

Instrument transformers (ITs) once installed in the field are seldom calibrated. We propose two tests to detect systematic errors in capacitive voltage transformers (CVTs) and current transformers (CTs). The first test, a direct test, compares the mid-point voltage estimated from both ends of a transmission line using PMU data. The second test, an indirect test, analyzes the deviation of the estimated positive sequence line parameter values from the design values. Subsequently, we propose a robust method to simultaneously determine the positive sequence line parameters and IT calibration factors. Special care is given to numerical sensitivity of the method to the noise in the data and we show by Monte Carlo simulations that the proposed approach is accurate and robust. A noteworthy feature of this paper are the case studies based on field PMU data for short, medium, and long length lines of 400 kV and 765 kV. It clearly demonstrates the stability of both line parameters and IT calibration factors and hence justifies the claims. [ABSTRACT FROM AUTHOR]

We consider the problem of fair allocation of the cost of a transmission system among load and generation entities using the marginal participation approach. We show that a cost-causal approach involving capacity-based line cost rate and a min-max fair economic slack bus selection for price-taking entities leads to a rigorously fair and more accurate implementation of marginal participation method. In the existing methods the counter-flows are masked, which is a compromise with fairness and linearity. However, if the counter-flows are incentivized then it can lead to pay-offs to some entities. The proposed approach solves the problem of pay-offs without masking the counter-flows. This is achieved by separation of the total transmission services cost into usage, reliability and residual capacity components. The allocation of the first two components is based on the min-max fairness policy, and the residual capacity costs are allocated on a pro-rata basis. Simulation results on multiple IEEE test systems, Indian utility power systems and extensive comparative evaluations for the contemporary methods demonstrate the claims made. [ABSTRACT FROM AUTHOR]

Fourteen novel dipeptide carboxamide derivatives bearing benzensulphonamoyl propanamide were synthesized and characterized using 1H NMR, 13C NMR, FTIR and MS spectroscopic techniques. In vivo antimalarial and in vitro antimicrobial studies were carried out on these synthesized compounds. Molecular docking, haematological analysis, liver and kidney function tests were also evaluated to assess the effect of the compounds on the organs. At 200 mg/kg body weight, 7i inhibited the multiplication of the parasite by 81.38% on day 12 of post-treatment exposure. This was comparable to the 82.34% reduction with artemisinin. The minimum inhibitory concentration (MIC) in µM ranged from 0.03 to 2.34 with 7h having MIC of 0.03 µM against Plasmodium falciparium. The in vitro antibacterial activity of the compounds against some clinically isolated bacteria strains showed varied activities with some of the new compounds showing better activities against the bacteria and the fungi more than the reference drug ciprofloxacin and fluconazole. [ABSTRACT FROM AUTHOR]

We propose an integer linear programming (ILP) formulation for the minimum relay break point set (BPS) computation. Subsequently, in the ILP framework, we propose an alternate maximum-independent relay BPS formulation with the intention of minimizing dependency within the BPS. We show that 1) in practice, the relaxed version of the ILP suffices to obtain an integral vertex and 2) the relaxed version of the ILP can be efficiently solved by the dual-simplex method. The performance of the proposed algorithm is compared and contrasted with existing algorithms. Case studies on various test systems show the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

Ischemic heart disease is the most common cause of death in patients with chronic kidney disease (CKD). Patients with CKD who develop an acute coronary syndrome (ACS) have a poor prognosis, with >70% mortality at 2 years. Despite this heavy burden of disease, the optimal management of ACS in this patient population is unknown. Our goal was to compare the effect of coronary revascularization or medical therapy alone on the long-term survival of patients with CKD presenting with ACS. From 1990 to 1998, data were prospectively collected on 4,758 patients admitted to a coronary care unit with the diagnosis of ACS. Of these, 3,104 had preserved renal function, and 1,654 had significant renal dysfunction, as defined by the National Kidney Foundation in the Kidney Disease Outcomes Quality Initiative classification of kidney function as an estimated glomerular filtration rate of <60 ml/min/1.73 m(2). Long-term survival was assessed and outcomes were compared according to whether patients were treated with medical therapy alone or if they underwent a percutaneous or surgical revascularization procedure. Follow-up information was available in 99% of the patients up to 8 years after the index hospitalization. Of the 1,654 patients with significant renal dysfunction, 64 underwent coronary artery bypass surgery, 232 underwent percutaneous coronary revascularization, 280 underwent a diagnostic cardiac catheterization and were subsequently treated medically, whereas 1,078 were treated with medical therapy alone. Percutaneous coronary revascularization was associated with superior long-term survival. In conclusion, patients with severe CKD and ACS had improved long-term survival when treated with percutaneous coronary revascularization. [ABSTRACT FROM AUTHOR]

This paper addresses various aspects of optimal phasor measurement unit (PMU) placement problem. We propose a procedure for multistaging of PMU placement in a given time horizon using an integer linear programming (ILP) framework. Hitherto, modeling of zero injection constraints had been a challenge due to the intrinsic nonlinearity associated with it. We show that zero injection constraints can also be modeled as linear constraints in an ILP framework. Minimum PMU placement problem has multiple solutions. We propose two indices, viz, BOI and SORI, to further rank these multiple solutions, where BOI is Bus Observability Index giving a measure of number of PMUs observing a given bus and SORI is System Observability Redundancy Index giving sum of all BOI for a system. Results on IEEE 118 bus system have been presented. Results indicate that: 1) optimal phasing of PMUs can be computed efficiently; 2) proposed method of modeling zero injection constraints improve computational performance; and 3) BOI and SORI help in improving the quality of PMU placement. [ABSTRACT FROM AUTHOR]

A capacitor in series with a transmission line is protected from overvoltage due to a large fault current by a nonlinear metal-oxide varistor (MOV) connected in parallel. Fault analysis, as well as the evaluation of performance of the transmission protection system, in the presence of MOV action becomes complex because 1) v-i characteristics of the MOV are nonlinear; 2) unsymmetrical MOV action for unsymmetrical faults will introduce coupling in sequence networks; and 3) MOV action will influence voltage or current inversion phenomenon. This paper presents a computationally efficient and simple methodology for fault analysis wherein the linear part of the network is modeled by an equivalent multiport Thevenin network. The proposed approach handles nonlinearity in fault analysis efficiently. It also provides an elegant approach to model unbalance in a network due to MOV action. The proposed approach can be used to determine relays prone to voltage or current inversion. Results on a real-life 716-bus Indian system illustrate the efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper proposes an expert system approach to short-term expansion planning (STEP). The rules which drive STEP can be classified into MW, MVAR, and ampacity management rules. MW and ampacity management rules are for alleviating transmission line congestion. Reactive power management is required for voltage control at load busses, conformity to the capacity curve of the generators, and containing the MW losses within acceptable limits. Embedding reactive power management in STEP is a challenging task since ac load flow may not converge in absence of proper reactive power planning and load modeling. Therefore, we also propose enhancements to the fast decoupled load flow algorithm for on-the-fly reactive power management. The enhanced algorithm not only can detect divergent load flow scenarios but also self-correct it by restarting the whole process with greater degree of freedom in reactive power controls. The proposed approach leads to development of an automated tool for STEP which has the capability to work, even with incomplete information. A simple method for evaluating location and requirement of shunt reactor is also proposed. By analysis and comparative evaluation, we show that the proposed system can arrive at a solution which is close to optimal. Results on the Western Regional Grid of India with an approximate load of 28000 MW and 1200 nodes are presented to demonstrate effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Availability Based Tariff (ABT) has been implemented in all the regional grids of India for improving grid discipline by frequency dependent pricing. Currently it is limited to short-term energy transactions between the beneficiary States and Central generating stations without the need for negotiations on price or quantum in real time. In the present scenario, Independent Power Producers (IPP), Captive Power Plants (CPP), small Distributed Generation (DG) like mini-turbine, fuel cell, etc., are not considered under ABT. DG units are normally modular in size and they can be placed close to consumers so as to reduce the T&D costs and losses. Hence, they need to be encouraged so as to meet the ever-increasing electricity demands of Indian power sector within the financial constraints. In this paper, impact of IPPs, CPPs and DGs on intra-State ABT is studied. This paper also proposes to study the impact of grid connected DG on network availability and reliability. The improvement in system reliability is studied after evaluating reliability indices like SAIFI, SAIDI, etc., with the inclusion of DG. [ABSTRACT FROM AUTHOR]

Examines the optimal bidding for generating companies in a deregulated power market based on the Markov decision process (MDP). Role of energy auction in the deregulated power system; Types of energy auctions; Discussion on MDP.