A heuristic and algorithmic approach to VAR planning

The authors present a knowledge- and algorithm-based approach to voltampere-reactive (VAr) planning in a transmission system. The VAr planning problem involves the determination of locations and sizes of new compensators considering contingencies and voltage collapse problems in a power system. An expert system model analyzes the operating conditions of a power system and suggests one or more of the P-V, Q-V and S-V (S denotes the system complex power) curves for use in assessing the voltage collapse problem. A second expert system module suggests control actions with the existing VAr controllers and sizes and locations for the installation of new compensators. The IEEE 30-bus system was used to demonstrate the capability of the proposed approach     

Multiple hypotheses and their credibility in on-line faultdiagnosis

In this study, a new method that handles multiple hypotheses is presented for fault diagnosis using sequence of event recorders (SERs). To quantify the certainty of hypotheses, a method to calculate their credibility is provided. The proposed techniques are integrated in a generalized alarm analysis module (GAAM) and have been tested with numerous scenarios from the Italian power system     

A Petri net algorithm for scheduling of generic restoration actions

This paper is concerned with scheduling of the restoration actions. Generic restoration actions (GRAs) have been identified in the authors' previous research based on a variety of restoration strategies used by electric utilities. This paper proposed a scheduling method using the Petri net (PN) techniques. The PN model incorporates the conditions that have to be met before an action can be taken. The time required to perform an action is also modeled in the net. A token passing and a backward search process are used to identify the sequence of restoration actions and their timing. The advantages of the proposed methods are: (1) the time required to restore a subsystem can be estimated; (2) a systematical method is obtained for identification of the sequence of actions. The BN method has been tested with simulation cases     

Characterization of the Survival Influential Genes in Carcinogenesis

The genes influencing cancer patient mortality have been studied by survival analysis for many years. However, most studies utilized them only to support their findings associated with patient prognosis: their roles in carcinogenesis have not yet been revealed. Herein, we applied an in silico approach, integrating the Cox regression model with effect size estimated by the Monte Carlo algorithm, to screen survival-influential genes in more than 6000 tumor samples across 16 cancer types. We observed that the survival-influential genes had cancer-dependent properties. Moreover, the functional modules formed by the harmful genes were consistently associated with cell cycle in 12 out of the 16 cancer types and pan-cancer, showing that dysregulation of the cell cycle could harm patient prognosis in cancer. The functional modules formed by the protective genes are more diverse in cancers; the most prevalent functions are relevant for immune response, implying that patients with different cancer types might develop different mechanisms against carcinogenesis. We also identified a harmful set of 10 genes, with potential as prognostic biomarkers in pan-cancer. Briefly, our results demonstrated that the survival-influential genes could reveal underlying mechanisms in carcinogenesis and might provide clues for developing therapeutic targets for cancers.     

Empirical Analysis of the Impact of 2003 Blackout on Security Values of U.S. Utilities and Electrical Equipment Manufacturing Firms

On August 14, 2003, the U.S. faced the largest blackout in history, which left over 50 million people without electricity in eight U.S. states and part of Canada. This paper investigates the effects of the blackout on the security values of the U.S. electric utilities and manufacturing firms in the electric power equipment industry, using an event study method. The results of this empirical study show that the electric utilities were negatively affected, but the electrical equipment manufacturing firms were significantly, positively affected.     

Dynamic mechanisms of voltage collapse

This paper presents the result of a thorough voltage stability analysis of a simple power system. Three mechanisms of dynamic voltage collapse are incorporated: generator excitation limit, load dynamics and on-load tap-changer. The effect of each individual mechanism is analyzed first and then the combined effects are used to reconstruct a voltage collapse. It is observed that the voltage stability region shrinks as the generator operates at the excitation limit. It is also found that the appropriate time to lock the on-load tap-changer is when the system trajectory enters the region where the load voltage increases.     

Consistency evaluation in an operational environment involving manytransactions

Energy transactions between electric power companies are commonly used to reduce operating costs. With movements toward a further de-regulated power industry, the number and importance of contracts are expected to increase. This paper proposes a new method to quickly and systematically evaluate potential contracts. A fundamental concern of contract analysis is whether or not the contract is feasible, i.e., if the terms of the contract, can be met without violating system operating constraints or prior contractual constraints. The novel features of our approach are a model of the essential components of a contract using rules and a contract consistency checking algorithm based on rule inference techniques. An example shows how the method is used to evaluate the consistency of a potential contract with existing contracts and other system constraints. The proposed method can help avoid tedious contract evaluation tasks while systematically ensuring that all constraints are met     

Effects of micropore development on the physicochemical properties of KOH-activated carbons

Effects of micropore development through varying the KOH/char ratio on the porous, electrochemical, electronic, and adsorptive properties for corncob-derived activated carbons (ACs) prepared by means of the KOH activation method were systematically compared. The pore properties of ACs, including BET surface area, total pore volume, micropore volume ratio, bulk density, and product yield based on the raw material were investigated to gain an understanding for the influence of KOH dosage on the pore development. Element analysis and temperature-programming desorption (TPD) were used to obtain the information of chemical composition and surface oxygen functional groups on ACs in order to propose the reaction mechanism of KOH activation. Based on the pore development, KOH-activated carbons can be classified into two groups: a combination of physical activation and chemical KOH etching at low KOH/char ratios (0.5-2) as well as chemically uniform etching at high KOH/char ratios (≥3.0). From the adsorption study for five organics with molecular weights varying from 129 to 466 g/mol, the specific adsorption capacity of ACs for organics is independent of their specific surface area. The specific capacitance of ACs reached a maximum as the KOH/char ratio was equal to 3, attributed to a compromise between the specific surface area and electronic resistance of ACs.     

Financial risk management in a competitive electricity market

This paper proposes solutions for electricity producers in the field of financial risk management for electric energy contract evaluation. The efficient frontier is used as a tool to identify the preferred portfolio of contracts. Each portfolio has a probability density function for the profit. For important scheduling policies, closed form solutions are found for the amount of futures contracts that correspond to the efficient frontier. Production scheduling must consider resource constraints. It is found that, without resource constraints, the portfolio with the highest expected profit can be preferred-even for a risk-averse decision-maker. When resource constraints are present, portfolios not corresponding to the maximum expected profit criteria will more frequently be preferred     

Viscosity and working efficiency analysis of soybean oil based bio-lubricants

This article presents significant data about viscosity and working efficiency analysis for developing the soybean oil based bio-lubricants. A suitable viscosity or viscosity index (VI) plays a very important role in a lubricant, which can avoid collision and rubbing between components of mechanical devices in work as well as optimize working efficiency of a machine. In general, low friction between devices can increase working efficiency of a machine, but low viscosity of a lubricant will easily cause collision and rubbing between components of mechanical devices in work. A too viscous lubricant also requires a large amount of energy to move, but a too thin lubricant will easily cause rubbed devices and increased friction. To replace the mineral oils and syntholubes, the soybean oil is recently become one of the most actively studied oils due to its eco-friendly organic property and lower cost. This work used mixtures of the original soybean oil, the epoxidized soybean oil, and the hydrogenated soybean oil as the base oils. Applications are focused on developing engine bio-lubricants. The results show that the epoxidized soybean oil has extremely large viscosity in comparison with the engine lubricants as well as the original soybean oil, whereas the hydrogenated soybean oil is clearly opposite. This viscosity analysis offers good informations to fit viscosity of the engine lubricants by mixing the three soybean oils as base oils.