In power system, stability problem and problems with electromechanical oscillations or generators swinging are consistent in power system. Electromechanical oscillations are noticeable in characteristic variables of synchronous generators. Consequences of synchronous generator connecting on grid are physical nature, apropos more generators connecting on one power system. The responses of power system on any system disturbance are electromechanical oscillations. Oscillations can be low damped or undamped with constant or increasing amplitude, so they can achieve value which can disrupt the system operation. The monitoring of power system electromechanical oscillations is very important in the frame of modern power system management and control. This paper presents techniques for identification and analysis of low-frequency oscillations. Simulations and analysis shall be performed on two-area test system.

Aim. The aim of the present paper is to compare the use ofArtificial Neural Network (ANN) to APACHE II, MOF, TISS-28 and MPI scoring system in prediction of peritonitis-relateddeath in patients with perforative peritonitis. Patients andmethods. A prospective study was performed of 145 patientswith perforative peritonitis, treated in the Surgical IntensiveCare Unit. The main outcome of this study was peritonitisrelateddeath. The Levenberg-Marquardt method was usedfor training, and 16 variables for entrance into the ArtificialNeural Network. Sensitivity and specificity of scoring systemsare graphically shown for the different values of cut-off pointswith the receiver-operating characteristic curve (ROC) curve.Results. We tested 92 cases in a network and found that theAPACHE II system predicted the lowest number of wrongassessments with a score of 12, with all the other scoringsystems predicting 19 wrong assessments. The area underthe curve for the first postoperative day was 0.87 for TISS-28score, 0.86 for APACHE II score, 0.83 for MOF and 0.72 forMPI score. The highest rate of correlation between the observedand the expected mortality rate was in the APACHEII system. This demonstrated that TISS-28 and APACHE IIare significantly better than other systems (P<0.01). In addition,this discriminatory ability was also retained on the thirdand seventh postoperative days. Conclusion. APACHE II issuperior in the prediction of patient outcome to the ArtificialNeural Network and other tested scoring systems.

The aim of this study was to evaluate the results of single-session sclerotherapy with mixture of alcohol and polidocanol and a subsequent injection of albendazole for devisceration of hydatid cysts in the spleen. Eight patients (four women and four men, average age 22.9+/-11.4 with hydatid cyst in the spleen were treated with 10 minutes time of exposure to mixture of ethanol 95% and polidocanol 1%. After that, 2 to 5 ml of albendazole was injected into the cyst cavity. Two patients had 2 cysts. At follow-up the patients were examined with clinical and biochemical examinations, ultrasonography, and serologic test for echinococcal antibody titres. The mean hospital stay was 2.5+/-0.93 days. During the follow-up period, mean cyst diameter decreased from 46+/-16.4 mm to 13.6+/-16.26 mm. In all ten cysts, a reduction of post procedural recolection of fluid over 40% was observed. Five cysts (50%) disappeared during the follow-up period. All cysts (5) smaller then 50 mm in diameter disappeared during follow-up period. After an initial rise, the echinococcal-antibody titres fell progressively and at the last follow-up were negative (< 1: 160) in 7 (88%) patients. No complications were observed, except for pain, fever and urticaria during the first 24-hours after the procedure. Sclerotherapy using only one session and 10 min time of exposure to the mixture of ethanol and polidocanol, and a subsequent injection of albendasole solution represents an effective treatment of hydatid cysts in the spleen. This procedure is even more efficacious for hydatid cyst with diametar smaller then 50 mm.

The analysis of the power transformer electromagnetic dissipation has been based on the analysis of electromagnetic process distribution in the stationary regime. The finite element method was used in the area of the numerical calculation of magnetic field. The 2D calculation of magnetic field distribution in transformers was realized through the application of the FEM2D software. From the numerical calculation of the magnetic field, the dissipating inductivity is calculated through the application of the energy method and the linked fluxes method. Based on the laboratory measures conducted on the model of a low-voltage transformer, the values of the numerical calculation have been provided. Results of the numerical calculation of the dissipating inductivities were compared to the measured values obtained in the short circuit regime with the application of very precise instrumentation. Some proportional deviations were noted. Conducted analysis on the numerical calculation of magnetic dissipation from the point of data accuracy, and complexity of the calculation brings the energy method into first place. The acceptable results have also been exercised with the linked fluxes method.

The common cases of a nonselective operation of the phase to ground fault protection in the insulated power grids, which utilize inductive sensors for a voltage unbalance indication, are explained by ferroresonant processes in voltage transformers of healthy drains. This paper deals with phase to ground faults simulations in a known grid, that provide information about possible nonselective phase to ground faults protection operation.

The validation of a power system clustering algorithm proposed by Glavic et al. on a real-life power system, the Bosnian electric power system, is presented. Voltage collapse is associated with a stress condition of the power system. Theoretical investigations of this complex phenomenon have resulted in many different analyses and solutions. It has been confirmed that the voltage instability problems start locally at the weakest nodes in a reduced area of the network, and the problem spreads to neighbouring nodes, resulting in a cascading phenomenon. Identification of reduced areas in a power system, with coherent behaviour of node voltages, may reduce the computational burden for voltage collapse analysis. A network clustering is proposed to reduce the computational burden associated with the analysis of voltage instability in large power networks. The algorithm is based on a method which was initially developed for coherency based system decomposition into study and external areas based on the linearised dynamic model of power system (satisfactory results have been obtained using the 30-bus New England test system). The algorithm is disturbance-independent, computationally fast and avoids computational burden because it requires only a limited number of basic arithmetic operations on the reduced Jacobian matrix of the load flow model.