55 research outputs found
Study selection and measures improve the reliability of power supply system transformer substation 35/10 kV
Experimental investigation of dependence light flow from duty cycle and power of high-pressure sodium lamp
Single-stage electronic ballast with power factor corrector
У роботі розглянуто високочастотний електронний пускорегулювальний апарат з корекцією коефіцієнта потужності для розрядних джерел світла. В однокаскадному апараті поєднано понижувальний перетворювач напруги та напівмостовий резонансний інвертор напруги. Понижувальний перетворювач напруги в режимі переривчастого струму працює як коректор коефіцієнта потужності. Отримано аналітичні залежності для проектування апарата. Результати аналізу, моделювання та експерименту добре узгоджуються між собою.Single-stage high-frequency electronic ballast with power factor corrector discharge lamps is presented in this paper. The proposed ballast is the combination of a buck converter and a half-bridge series-resonant parallel-loaded voltage inverter. The buck semistage works in the discontinuous conduction mode as a power factor corrector. The analytical expressions for ballast design are derived. The analysis, simulation and experimental results are in good agreement
Evaluation of the two-photon exchange diagrams for the electron configuration in Li-like ions
We present ab initio calculations of the complete gauge-invariant set of
two-photon exchange graphs for the electron configuration in
Li-like ions. These calculations are an important step towards the precise
theoretical determination of the - transition energy in the
framework of QED.Comment: 17 pages, 6 figure
Automatic system for relay protection from ground faults
Наведено алгоритм, що використовує значення амплітуди вектора початкового нульового струму приєднання з пошкодженням і кута між цим вектором і вектором міжфазної напруги для відомого режиму розподільної мережі. Він дозволяє однозначно визначати відстань до місця пошкодження ізоляції і значення опору цього пошкодження.The algorithm which uses the value of the damaged connection initial zero current vector amplitude and the angle between this vector and the vector of the interphase voltage for the given mode of distribution network is given in the article. It allows to find the distance to the place of the isolation damage and the value of this damage resistance.
The most typical type of damages in these networks are monophase ground faults which result in the isolation break down in its weakened places. Similar damages are caused by the isolation ageing, that is why the problem of providing efficient continuous control of the isolation, its detection in proper time and trouble clearing is still very actual.
The purpose of our work is to improve the method of finding the distance to the place of the local isolation damage and this damage resistance in the distribution networks, which would allow to find not only the distance to the ground faults, but to the local isolation damages, as well as to find the resistance of the isolation local damage. It is possible due to the determination of the initial zero currents vector amplitude and the angle between the vector of this current and the vector of the interphase voltage. Experimental data are compared with those obtained on the mathematic model of the network while calculating step-by-step change of the place of the predictable isolation damage along the damaged connection and the change on each step the value of resistance in the place of the isolation damage from a zero to the maximum possible.
Automatic system controls continuously the amplitude of the initial zero currents of all connections. Exceeding of the given value in one of the connections is treated as appearance of the isolation damage, being a ground fault in particular. As a result according to the change of place and the damage resistanse value, the cyclic process of finding the mathematic model parameters, which are equal to those of displacement of the predicted place of the isolation damage, starts. Besides, in every stage of calculation the cycle of the predicted damage value change from zero to the maximum possible is carried out. The calculated results of the initial zero current vector in every step is compared with the actual vector of the initial zero current of the damaged connection. When the actual and calculated vectors of the initial zero current coincide, calculated values are provided in the distance, which were used in this step of calculation.
The change of the network configuration is taken into mathematical model automatically while including and excluding of the corresponding element of the network. To simplify the external connections of the system hand-operated correction of the network model under change of its configuration is used.
Initial zero currents phase is found according to the relation to the vector of the interphase voltage. This voltage vector does not change the amplitude, when the isolation damages of different size of the transition resistance up to the ground faults, appear. Besides, the change of phases between the vector of voltage and the initial zero currents practically does not depend on the place and the size of the isolation damage
Implication of computed corrections at the procedure of automatic compensation of systematic errors
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