The problem of choosing the variable parameters of a stabilizer of an object which minimize an additive quadratic integral functional reflecting the complex of requirements for a closed stabilization system is considered. To solve the problem a combined method of parametric synthesis of the stabilizer, which is a sequential combination of the Sobol grid method and the Nelder-Mead method, is proposed. At the first stage of the method by applying the Sobolev grid method a working point of the closed system in the pace of its variable parameters is transferred into a neighborhood of the quality functional global minimum point. Then at the second stage the Nelder-Mead method is used to relocated the working point into a small neighborhood of the global minimum. The method proposed comprises a particular algorithm for choosing the weight coefficient of the additive quality functional as well as makes use of the stabilization object state vector main coordinates, which provide the most adequate description of its dynamic features. The properties of a mathematical model of controlled system with discontinuous stabilization process control are studied numerically. The analysis of the plots in the dynamical system state phase space indicates non-spiral approach of the system to its equilibrium state. The synthesized control is realized in the form of a sequence of switchovers.
Main concepts of the method of computational evaluation of moisture content in solid insulation of power transformers by with the use of results of measurement of dielectric characteristics are presented.Moisture content of solid insulation of power transformers is determined before startup and in overhauls from the moisture content of insulation specimens placed into the tank [1]. During operation of a transformer it is permissible to calculate the moisture content of solid insulation. However, the guideline contains no method for calculating the moisture content of solid insulation of transformer windings based on data obtained by measurement of dielectric characteristics.In the present paper we use the experience accumulated in recent years on the state of transformer equipment, results of the works performed by VNIIÉ and the "ZTZ Servis" Company (Zaporozh'e, Ukraine), and recommendations of CIGRE and MEC for developing a methodological approach to evaluation of the moisture content of insulation of power transformers by computation.It is mentioned in [2] that the diagnostic value of the method of computational evaluation of the moisture content of solid insulation is higher than that of the method of analysis of specimens inserted into the tank, because though it gives an approximate value of the moisture content, the latter is determined directly for the insulation and allows for the temperature. The mean value of the moisture content in the insulation is determined indirectly in terms of the measured tangent of the dielectric loss angle of the insulation with allowance for the temperature of the winding and the tangent of the dielectric loss angle of the oil. Figure 1 presents the dependence of the tangent of the angle of dielectric loss tan ä of oil-impregnated cellulose insulation on the temperature and moisture content [3]. It can be seen from Fig. 1 that at 2% moisture content the tangent of the dielectric loss angle increases by about of a factor of 1.5 with growth in the temperature from 20 to 60°C.At very low moisture content of about (0.5 -1)% the dependence of the tangent of the dielectric loss angle has a characteristic U-shape, and the change in the temperature from 20 to 60°C affects little the tangent of the dielectric loss angle, i.e., the relative change (decrease) is less than 10%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.