Volume 4, No. 11 (2005)

TRANSFORMER FAULT SIMULATION BASED ON DIFFERENT TRANSFORMER MODEL APPROACH

CIPCIGAN LIANA, CHINDRIS M., RUSU ADRIAN, RASHED K.

This paper investigates the abnormal system behaviour under conditions of transformer faults. A power sub-system configuration has been employed for the simulations using dedicated electromagnetic transient simulation package PSCAD/EMTDC. The events in the power system encompass many scenarios, including various faults and normal operating states, and correspond to specific time scales. The diversity of the cases has been achieved by changing the type of fault (single line-to-ground fault, double line-to-ground fault) and time to apply the fault. In the event of a fault it is important to be able to reconstruct and have evidence of the surrounding circumstances and the timing of the disturbance as well as the faults` modes, or ways in which the circuit breaker fails. This study presents the simulation techniques for the currents that may occur in the network under different fault conditions. These short circuit currents determine the rating of circuit breakers that must be able to clear the fault in order to avoid permanent damage to the equipment. Using different transformer models available in PSCAD/EMTDC software package the results obtained are different.

ABOUT THE SPACE ELECTRIZATION OF LOW-CONDUCTIVE DIELECTRICS AND ITS INFLUENCE ON THE EQUIPMENT RELIABILITY AND FACILITIES OF POWER ENGINEERING

GROSU FLORIN, BOLOGA M.K.

The supposition is stated that conductivity is a functional of the electric field strength. By isolating a “charged” conductivity component an equation has been obtained for the charge density, and its solution has been found. The limiting cases have been considered. It has been shown that the distribution of space charges ρ is not stable. The method of its experimental determination in a dielectric plane-parallel layer is described.

THE FAILURE CAUSES OF THE FUNCTIONAL SUBSYSTEMS AND THEIR COMPONENTS FROM HPP TILEAGD

HORA CRISTINA, VEREŞ MIRCEA, CATANASE ADRIANA, HORA HOREA

The paper aims to identify the failure of the components and elements and the evaluation of their consequence on the functioning of the functional subsystems (installations, equipments) from an HPP.On the basis of the values of randomize variable lifetime (LT) and maintenance correcting time (TMC), defined in the previous paper, they were determined the indicators of operational reliability at the level of hydro- generator group and there subsystems.With the view of identification and hierarchy the impact of component elements on the reliability of the groups, it was done in the paper an analysis of the failures causes for each subsystems of group not only under the aspects of faults interval but also of the number faults. The obtained results being represented under graphical form.

THE OPERATIONAL RELIABILITY INDICATORS AT THE LEVEL OF THE HYDRO-GENERATOR GROUP FROM HPP TILEAGD, ROMANIA

HORA CRISTINA, VEREŞ MIRCEA, CATANASE ADRIANA, HORA HOREA

The operational reliability studies of equipments from the hydroelectric power plant (HPP) are indispensable to obtain data to determine reliability indicators with adequate credibility.To evaluate the operational reliability indicators of the hydro-generator groups from HPP Tileagd, we detailed the analysis to the level of the next subsystems of these: the globe valve (GV), hydraulic turbine (HT), interacting automatic control system (governor + pressure oil group) (ACS), hydro-generator (HG), group transformer (GT)Using statistic data obtained from exploitation of hydro-power plant Tileagd, we composed a compendium with commentary referring to reliability indicators values, the distribution functions of randomized variables.

SYSTEMICALLY CONNECTIONS IN THEORETICAL AND PRACTICAL RELIABILITY

IVAS DUMITRU, MUNTEANU FLORIN, NEMEŞ CIPRIAN

This paper presents the main reliability connection principles between elements or systems with a view to develop new methods to calculate the optimum values of reliability parameters. There are many techniques to obtain a specified level of reliability and the authors propose some models to estimate the optimal values of these parameters.

RISK ASSESSMENT METHOD FOR A MUNICIPAL WASTE INCINERATOR LOCALIZED IN AN URBAN AREA

LECA AURELIU, NEGREANU GABRIEL, PETCU ANDREIA

This paper debate the risk assessment from a municipal waste incinerator for population health and environmental. In the base of input date about "classical" pollutants emissions (SO2, NOx, CO, particles and their secondary aerosols such as sulfates) and toxic metals (As, Cd, Cr, Hg, Ni and Pb) to the atmosphere it is determinate the risk and the damage costs using the software RiskPoll . These aspects can be quantified using a transparent methodology, easy to implement and who requires just few input data values.The emphasis is to obtain a reasonably accurate and relevant approximation of the impacts using a "simplified" approach. The following steps are fundamentals: select an impact assessment model; specify input data; calculate impact estimates; review results; perform sensitivity analyses.