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Partiendo del enfoque de Robert Lucas (1988), este trabajo desarrolla unmodelo de crecimiento endógeno que considera dos efectos de la acumulaciónde capital humano: el primero de orden interno, que mide el impactosobre la productividad de cada persona y el segundo de orden externo,relacionado con la contribución a la productividad de los demás factoresde producción. Para los propósitos del ejercicio, la propuesta de Lucasse complementa con la descomposición del factor tecnológico en dos componentes,uno exógeno y otro endógeno, de acuerdo a las interaccionesentre el capital humano y el cambio técnico.

This paper proposes a methodology to include HVDC-wind powerconnection schemes to the transmission expansion planning. The methodology includes the identification of specific problems, the definition of alternatives of interconnection, and the definition of selection criteria and, finally, the selection of the best alternative (using the Cost Minimization Function) based on economic and technical parameters. Investment cost, operational cost and non-supplied energy costs are calculated for the analysis of each interconnection alternative formulated. Moreover, each alternative fulfill the N-1 criteria that indicatesthe systemsatisfies operational criteriawhen any component of the system is out of service. The exposed methodology is tested on two differentsystems; one of these is the Colombian Interconnected System. This considers future interconnection of wind parks in La Guajira (Colombia) with a total power of 3200MW (more than 20% of the installed capacity on the country), highlighting that the collector of this wind park is more than 100km away from the closest Colombian Electrical System substation, adding more restrictions on its connection. [ABSTRACT FROM AUTHOR]

Current and traditional methods of load shedding are based on threshold values of frequency and voltage; thus, when the power system falls below these values, some mechanical control actions are activated as countermeasure against stability problems. Nevertheless, in many cases the traditional mitigation methods based on load shedding cannot ensure that the network remains in continuous operation after the presence of suddenly and severe perturbations. In addition, the development of control systems of wide area based on PMC's measurements has allowed the development of different kinds of indices for the stability prediction. Thus, on-line diagnosis of the power system about angular stability and voltage stability gives better information about the system's situational awareness. This paper proposes a methodology that allows the system operator to take a decision if applying the toad shedding as a countermeasure for system instabilities caused by severe contingencies. In addition, the methodology identifies which are the nodes where the load shedding must be applied and the quantity of load shedding to be applied. The proposed load shedding methodology is based on a fuzzy logic decision method using the stability prediction index (SPI) and fast voltage stability index (FVSI). These indices can be computed on-line and they give the stability status of several operating areas. The methodology is tested on the NYPP-NETS of 68 nodes and it is illustrated with a cascade. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology for the computation of robust controls that guarantee robustness in a wide range of operating condition of a power system; such as contingencies, uncertainties and delays in the signals. This paper proposes a detailed modeling of uncertainties of the power system as additive uncertainties of the plant under the theory of robust control, and also a methodology for defining in a correct way sensitivity matrices used in the computation of robust controls and based on the model uncertainties and control purposes (damping of electromechanical oscillations). It is also proposed the computation of robust controls in two stages guaranteeing robustness and damping, and the analysis of performance of the control against delay times in control signals. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology through an optimization model that allows decisions about expansion of a power system considering intermittent renewable energy sources, like wind energy, and other random variables in transmission and generation expansion planning. So, the uncertainty of the risk of failure in the system components, uncertainty in demand and uncertainty in the availability of energy resources (wind speed for wind power generation) is included. The methodology is applicable to systems with a high level of hydroelectric sources. It is divided in two parts, the first one establishes the best location of intermittent sources, like wind energy. The second part optimizes the combination between renewable sources and conventional generation. After that, the transmission facilities are formulated and optimized. [ABSTRACT FROM AUTHOR]

A strategy to estimatethe power demand incrementfor Plug-in Electric Vehicles (PEV) penetration in residential customers is proposed. This is based on a stochastic model of arrivals and leavings of vehicles and has as goal to generate diversified load curves for every hour of a day, and so on, to estimate the power demand by Electric Vehicles. So, the proposed model is useful to be employed for planning purposes in distribution power systems. This study is divided in two cases, one of them has a limited number of chargers to be installed at residential customers and the second option has a free amount of charges related to number of Electric Vehicles; these represent different types of housing. This tool provides information for planning in distribution systems, based on specific information on mobility inthe city to study. [ABSTRACT FROM AUTHOR]

Situational awareness has become an important subject for the operation of power systems because it will give information of the state of functioning of the system and important data for taking control actions in the power systems. Among the different aspects to be included in the situational awareness to be monitored in a wide-area monitoring system, the supervision of the behavior of damping of electromechanical modes has an important role. It is well known that this supervision corresponds to an estimation process of dynamic characteristics in a non-linear system. However, an important balance between the requirements of quantity of data and time for estimation must be achieved for this important task. So, this article proposes the utilization of both fixed sliding-window and size-controlled window analysis to be used in on-line wide-area monitoring system based identification of electromechanical modes using a multi-Prony estimation. The proposed methods are simulated for the reduced-order equivalent of the interconnected New England Test System and New York Power System. [ABSTRACT FROM AUTHOR]

The special integrated protection systems (SIPS) are alternative tools in order to improve the security of power systems that have been developed or formulated to mitigate the impact of particular problems when a disturbance occurs in the power system. This paper proposes a methodology of planning focused in the selection of sets of SIPS in a joint analysis of angular stability, voltage stability and frequency stability using Fuzzy Analysis to take decisions. The methodology has been tested on the 68 nodes NEPS-NYPS system. [ABSTRACT FROM AUTHOR]

Sequential islanding is a strategy that consists of tripping off properly selected lines to separate the network into one or more islands as a way to improve the security of the power system. This paper proposes an application of some concepts of the spectral graph theory to identify the minimum cutset of transmission lines that allows the partitioning of a power system into several regions based on the minimum net flow between them. The approach provides an effective tool for the identification islands scenarios. The concepts are illustrated by splitting two large-scale systems. [ABSTRACT FROM AUTHOR]

It is expected that electric vehicles market growth is coming ahead due to ecological concern and energy efficiency maximization. As Plug-In Hybrid Electric Vehicles are by now the up to date development in the electric vehicles area and being aware of its plug to grid skills, it can be inferred that the new loads these represent could affect current electricity networks. This paper presents an alternative method to determine this load based on a statistical approach using random variables. At the end, a study case is portrayed to exemplify the above mentioned approach, some conclusions are expounded and targets of further work are set. [ABSTRACT FROM AUTHOR]

For studying the occurrence of high order failure scenarios (HOFS) in bulk power transmission systems, these authors presented in a previous issue of this journal a method based on stochastic point processes (SPP) modeling and Monte Carlo simulation (MCS) that in contrast to other ones can manage time varying failure rates and avoids the cumbersome task of elaborating a list of system operating states. Now, it has been upgraded in order to assess the effect of repairs on the occurrence of HOFS. For this, the repair service rendered in the power system is modeled using SPP and queuing theory concepts; this allows representing constant and time varying repair rates and diverse repair logistics, two features not offered by any other method. After applying this method to a test system, it is concluded that as more limited the resources for repairs are, higher is the risk of occurrence of HOFS. It is then recommended to consider this fact when planning the expansion and the operation of the bulk power transmission system. [ABSTRACT FROM AUTHOR]

The n-1 reliability criterion has been applied extensively for power systems because the loss of two or more components over a short period due to independent failures has traditionally been considered not credible. However, the post-mortem analysis of some blackouts has shown that these kinds of events do occur; hence, the question about what contingency level is relevant for bulk power transmission systems arises. In order to reply this question, a method for studying the occurrence of high order failure scenarios (HOFS) is presented in this paper; it is based on stochastic point process (SPP) modeling and Monte Carlo simulation (MCS). In contrast to traditional methods, it can include aging, currently a matter of great concern in the power industry, and does not require the elaboration of a list of system operating states, a cumbersome task even for small systems. Results obtained using the IEEE Reliability Test System show that independently of system size or the presence of aging HOFS of order 2 and 3 are the most relevant because they have higher probability of occurrence and lesser time span than others. It is then recommended to consider HOFS of these orders for the study of bulk power transmission systems. [ABSTRACT FROM AUTHOR]

This paper present a method for representing protective systems in reliability studies of the power system which condenses at the circuit breakers of the protection zone the effect of protective component failures, protective scheme configuration and preventive maintenance strategies. It combines the modeling of failure and repair processes using stochastic point process theory and a procedure of sequential Monte Carlo to artificially generate the operating sequence of the protective system and for computing the probabilities of failure to operate seen at the circuit breakers. Its main advantage is that it supports the use of time varying failure rates, a feature not offered by the other methods that have been traditionally applied for this task. On the other hand, its main disadvantage is the long computational time required by the simulation. [ABSTRACT FROM AUTHOR]

Time-delay is inherent to communications schemes in power systems, and in a closed loop strategy the presence of latencies increases inter-area oscillations and security problems in tie-lines. Recently, Wide Area Measurement Systems (WAMS) have been introduced to improve observability and overcome slow-rate communications from traditional Supervisory Control and Data Acquisition (SCADA). However, there is a need for tackling time-delays in control strategies based in WAMS. For this purpose, this paper proposes an Enhanced Time Delay Compensator (ETDC) approach which manages varying time delays introducing the perspective of network latency instead dead time; also, ETDC takes advantage of real signals and measurements transmission procedure in WAMS building a closed-loop memory control for power systems. The strength of the proposal was tested satisfactorily in a widely studied benchmark model in which inter-area oscillations were excited properly. [ABSTRACT FROM AUTHOR]

Discusses the identification of regions of the tomato gamma-glutamyl kinase that are involved in allosteric regulation by proline. Significance of osmoregulation to agriculture; Post-transcriptional control mechanism; Structure of a proline binding site.

Background: We undertook this study to describe prescription practices and the degree of disease control in a large sample of patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS) treated by rheumatologists in Mexico. Methods: Board-certified Mexican rheumatologists across the country were asked to assess consecutive RA and AS patients; 1208 patients completed a self-administered questionnaire with information on demographics, disease duration, co-morbidity, treatment, pain, disability and a validated Spanish version of instruments to measure physical function and quality of life. Results: Of the 1096 RA patients, 88.1% were treated with nonsteroidal anti-inflammatory drugs (NSAIDs), 1020 (93.3%) with disease-modifying anti-rheumatic drugs (DMARDs), 365 (33.4%) with steroids, and 70 (6.4%) with biological agents. Their mean Health Assessment Questionnaire Disability Index (HAQ-Di) score was 1.21 ± 0.80, Disease Activity Index, 28 joint count (DAS 28) 3.9 ± 1.29, and Rheumatoid Arthritis Disease Activity Index (RADAI), 3.94 ± 2.01. Regarding the 112 AS patients, 110 (98.2%) received NSAIDs, 90 (80.4%) were on DMARDs, 11 (9.8%) took steroids, and 11 (9.8%) received biological agents, their functional status shown as Bath Ankylosing Spondylitis Functional Index (BASFI) score of 4.4 ± 2.5. Among the 1110 DMARD users, only 64 received one drug, and a great proportion used two or more DMARDs; 81 subjects (16.2%) were on biological agents, in any combination. RA patients more commonly used methotrexate, 791 (72%) cases, and hydroxychloroquine. Taking into account their diagnosis, the combination most prescribed was NSAIDs plus DMARDs in 660 subjects (54.7%). Conclusions: DMARDs in combination with other drug are the most frequently prescribed therapeutic scheme for RA and AS patients. These schemes used for both conditions by Mexican rheumatologists are in line with current international recommendations. [Copyright &y& Elsevier]