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The accident rate of gas-insulated switchgears (GIS) is considered. The statistical sample covered 30 110-500 kV switchgear switchgears in a vast region of the European part of the country for the period 2008-2022. Their design features and technical characteristics are given. Significant and insignificant failures of GIS, including their structure, namely, distribution by elements of installations, technical and organizational causes of occurrence, dependence on the year of operation are subjected to analysis. The flow parameter (frequency) of GIS failures is determined, as well as the maximum possible time of GIS restoration after damage to the arc suppression chamber of the pole of the 500 kV circuit breaker. Comparative data are given with failure rate of GIS abroad and with gas-insulated circuit breaker cells in open switchgears.

The statistical analysis of overhead lines (OHL) of the unified national power grid (UNPG) of the Central European part of the country for the previous 15 years is subjected to statistical analysis. The structure of the failure flow parameter (failure frequency) of 220 and 500 kV overhead lines with a total length of 17.6 and 8.5 thousand kilometers, respectively, is compared. It is shown that the last decade is characterized by the most favorable reliability characteristics. At the same time, a tendency was detected, when the parameter of overhead line failure flow became insignificantly dependent on the nominal voltage of the network. This fact makes us doubt the existing belief of specialists, according to which the specific (per 100 km) failure rate of overhead transmission lines decreases with the increase of the nominal voltage of the network. The above trend once again demonstrates the objective possibility of purposeful management of electric networks reliability.

For an electric power system (EPS), as a dynamic system with many inputs and many outputs (Multi Inputs Multi Outputs System − MIMO), compact analytical formulas are obtained for calculating the coefficients of the controller matrix and the observer matrix of the state of the solution of the synthesis problem, providing a given placement of eigenvalues along full state vector. These formulas are generalizations to MIMO systems of the well-known Ackermann formula used to design the control of systems with one input and many outputs (Single Input Multi Outputs System − SIMO). The approach is based on the transformations used in the original multi-step (multilevel) decomposition method, as well as a nondegenerate similarity transformation in the form of the Kalman controllability matrix. The obtained formulas are applicable to dynamic systems, for which the dimension of the state space is a multiple of the dimension of the inputs (controls). This limitation is removed by using the Yokoyama transform. These formulas differ in terms of parameterization of the set of equivalent laws. An example of the synthesis of a control law for a synchronous generator in a complex EPS is considered in order to preserve the existing modes of electromechanical oscillations and meet additional requirements (roughness with respect to disturbances and/or increased sensitivity to changes in controlled parameters in a given region or frequency band).

The accident rate of 500 kV overhead lines (OHL) of a large region on a long time interval is researched. Significant fluctuations in the values of their failure rate (failure frequency) are revealed. The specified parameter was analyzed using the mathematical apparatus of the theory of deterministic (dynamic) chaos. The fractality of the time series of the OHL failure rate was revealed, as well as the positiveness of its maximal Lyapunov exponent, which indicated the chaotic nature of the dynamic process under consideration. The insignificant (less than five years) depth of forecasting the reliability characteristics of overhead lines due to the indicated chaotic state is substantiated. This is an unfavorable factor that reduces the reliability of the reliability estimates of the main grid of power systems.

The results of forecasting the failure rate (failure frequency) of overhead lines (OHL) 500 kV, presented in the form of a time series with signs of chaos, are presented. Predictive estimates are obtained using methods of singular spectrum analysis, neural and fuzzy neural networks. As an object of singular spectrum analysis, a delay matrix is used, which is formed on the basis of the time series of the failure rate. The prediction was carried out by means of one-step transformations of the initial data. For prediction using a neural network, a direct signal transmission network is used, trained by the backpropagation method. In order to achieve the minimum mean squared error, the training sample contained the maximum possible history. To predict the failure rate by the method of fuzzy neural networks, the Wang-Mendel network was chosen. In all prediction cases, within the framework of one prediction year, 10 thousand "training - prediction" cycles were performed, which ensured the stationarity property of the histograms of the failure rate distributions.

Algorithms for fast and superfast solvers of large systems of linear algebraic equations, used in solving mathematical problems of electric power industry, are proposed. These algorithms are constructed based on a novel method of multistep decomposition of a multidimensional linear dynamic system. Examples of the analytical synthesis of iterative solvers for matrices of the general form and for large numerical systems of linear algebraic equations are presented.

The accidents cyclicality of 500 kVoverhead lines of a large region over an extended time period was studied. Significant fluctuations in the values of their failure rate (failure frequency) under the impact of natural and socio-economic factors are revealed. The wavelet spectrums of the failure frequency were constructed, which revealed several historical periods of accidences. It is proposed to consider the failure rate as the output signal of a dynamic system with many difficultly formalized inputs. The stability of this dynamic system is evaluated. The ways of formalizing a multidimensional dynamic model of accidence in main electrical grids of power systems are outlined.

A solution is presented for the problem of placing phasor measurement unit to identify the mathematical model of the electric power system in the state space. The criterion for complete observability of the Kalman dynamic system is taken as a basis. As a method of solution, we use the canonical genetic algorithm. The complete observability of the power system is ensured by the application of the observability rule in the form of a recursive test of observability. The proposed approach is demonstrated by the arrangement of synchronized vector meters in the Kaliningrad region power system.

The algorithms for currents induced in a grounded lightning wire (LW) with single-phase short circuit (SC) calculation are considered. It is shown that the method of short-circuit current and current in LW simultaneous determination gives more correct results for the assessment of LW thermal resistance

A randomized algorithm for computing the invariant zeros of the electric energy system as a dynamical system with many inputs and many outputs (MIMO system), specified in the descriptor form, is proposed. Definitions of invariant zeros are carried out by randomizing the original MIMO system and it reduces to a generalized eigenvalue problem for a numerical matrix. The application of the algorithm is illustrated by the example of calculating the invariant zeros of the linear model of the United Power System.

An original method of reducing the equations of node voltages is proposed with the aim of equivalence of the electric network. The method is based on the matrix transformations of the indicated equations with the help of matrix annulators. It is shown that this method, in comparison with the traditional one, makes it possible to improve the conditionality of the solved equations by an order of magnitude or more. This has a significant effect on the numerical stability of the resulting electrical network equivalents. The results of reduction of a small, large, and very large system of nodal stress equations are presented.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2007.09.005 Byline: Thomas R. Anderson (a), Vladimir A. Ryabchenko (b), Michael J.R. Fasham (a), Victor A. Gorchakov (b) Keywords: Denitrification; Biogeochemical cycles; Ecosystem modelling; Detritus; Export flux; Arabian Sea Abstract: A three-dimensional hydrodynamic-ecosystem model was used to examine the factors determining the spatio-temporal distribution of denitrification in the Arabian Sea. The ecosystem model includes carbon and nitrogen as currencies, cycling of organic matter via detritus and dissolved organic matter, and both remineralization and denitrification as sinks for material exported below the euphotic zone. Model results captured the marked seasonality in plankton dynamics of the region, with characteristic blooms of chlorophyll in the coastal upwelling regions and central Arabian Sea during the southwest monsoon, and also in the northern Arabian Sea during the northeast monsoon as the mixed layer shoals. Predicted denitrification was 26.2TgNyr.sup.-1,the greatest seasonal contribution being during the northeast monsoon when primary production is co-located with the zone of anoxia. Detritus was the primary organic substrate consumed in denitrification (97%), with a small (3%) contribution by dissolved organic matter. Denitrification in the oxygen minimum zone was predicted to be fuelled almost entirely by organic matter supplied by particles sinking vertically from the euphotic zone above (0.73mmolNm.sup.-2 d.sup.-1) rather than from lateral transport of organic matter from elsewhere in the Arabian Sea (less than 0.01mmolNm.sup.-2 d.sup.-1). Analysis of the carbon budget in the zone of denitrification (north of 10[degrees]N and east of 55[degrees]E) indicates that the modelled vertical export flux of detritus, which is similar in magnitude to estimates from field data based on the.sup.234Th method, is sufficient to account for measured bacterial production below the euphotic zone in the Arabian Sea. Author Affiliation: (a) National Oceanography Centre, University of Southampton, Waterfront Campus, Southampton SO14 3ZH, UK (b) St. Petersburg Branch, P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, 30, Pervaya Liniya, 199053 St. Petersburg, Russia Article History: Received 6 June 2006; Revised 3 September 2007; Accepted 11 September 2007

We investigate the effect of variable marine biogeochemical light absorption on Indian Ocean sea surface temperature (SST) and how this affects the South Asian climate. In twin experiments with a regional Earth System Model, we found that the average SST is lower over most of the domain when variable marine biogeochemical light absorption is taken into account, compared to the reference experiment with a constant light attenuation coefficient equal to 0.06 m-1. The most significant deviations (more than 1 °C) in SST are observed in the summer period. A considerable cooling of subsurface layers occurs, and the thermocline shifts upward in the experiment with the activated biogeochemical impact. Also, the phytoplankton primary production becomes higher, especially during periods of winter and summer phytoplankton blooms. The effect of altered SST variability on climate was investigated by coupling the ocean models to a regional atmosphere model. We find the largest effects on the amount of precipitation, particularly during the monsoon season. In the Arabian Sea, the reduction of the transport of humidity across the equator leads to a reduction of the large-scale precipitation in the eastern part of the basin, reinforcing the reduction of the convective precipitation. In the Bay of Bengal, it increases the large-scale precipitation, countering convective precipitation decline. Thus, the key impacts of including the full biogeochemical coupling with corresponding light attenuation, which in turn depends on variable chlorophyll-a concentration, include the enhanced phytoplankton primary production, a shallower thermocline, decreased SST and water temperature in subsurface layers, with cascading effects upon the model ocean physics which further translates into altered atmosphere dynamics. [ABSTRACT FROM AUTHOR]