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The emerging smart grid requires more reliable communication technology. This paper presents a coded adaptive BFSK PLC solution for medium voltage power line communication with low SNR and frequency selective attenuation. The measure based powerline channel model in China is given first, then the data transmission system is proposed for MV PLC. Three centre frequencies is used to optimize data transmission,...
In this paper, on the basis of the analysis of power line channel characteristic,we firstly build a power line channel mode. And then, we elaborate the spectrum theory and its main performance indexes. At last, the direct sequence spread spectrum communication system is build by MATLAB/Simulink using the power line channel mode. The simulation results prove that the Spectrum-spread Technology can...
In this thesis, existing instability criterion and its stability indicator τ for autonomous single machine infinite-bus system (SMIB) are firstly given, which reflect convex-concave characteristics of the trajectory inΔω-δ phase-plane. On this basis, it is discussed that there are some problems when the instability criterion of autonomous SMIB system is used in non-autonomous SMIB system. Proceeding...
IEC 61850 based substation automation systems simplify the design, installation and maintenance with significantly reduced cost. Its real-time, security and reliability are of concern and are vital important to the industry. This paper presents the development and application of an established platform for evaluating process bus applications. The evaluation platform consists of a number of GOOSE,...
This paper presents a comprehensive simulation model for sequential tripping in DC traction system based on MATLAB/Simulink. With the introduction of practical operation of DC traction system, the scenario of “Large double end” feeding arrangement is under analysis. Based on this special scenario, the technique of simulation and protection scheme is presented. Moreover, the suggestion of setting value...
In the paper, the complete lightning model for HVDC transmission lines is presented, and the model is divided into five parts: lightning discharging model, insulator string flashover model, arrester model, tower model and conductor/ground wires model. The proposed lightning model was successfully tested in the PSCAD/EMTDC software. And the model is shown to be a potential tool for studying on lightning...
This paper mainly study on the model predictive control (MPC) based method in the emergency voltage control. The coordinated voltage control scheme and the MPC model of voltage control are introduced firstly. Next, the Lagrange decomposition and auxiliary problem principle is employed into the MPC model of voltage control and a distributed MPC based voltage control scheme can be obtained, by which...
In the paper a new method of high resistance fault detection meant for current differential protections of two-terminal transmission lines is presented. The method is based upon calculation of line differential admittance in pre-fault and in faulty conditions. As the ground fault current during high resistance faults is comparable and, sometimes for long transmission lines, even lower than the line...
Due to the fact that wide area information is easily disturbed, lost and distorted, while it is not fully considered in current wide area protection principle, a wide area backup protection algorithm with high fault-tolerance performance is proposed to implement the CSBPS(Centralized Substation Backup Protection System). After the fault-tolerance judgment, The CSBPS can locate the fault equipment...
This paper puts forward a new transformer self-adaptive protection principle. The principle is based on equivalent equation. The principle mainly includes three components: parameter estimation unit, high speed protection unit and fault component protection unit. When there is serious fault in transformer, the high speed protection unit can act quickly. When there is weak fault in transformer, the...
In this paper enhanced differential current protection scheme dedicated for HV transmission lines is described. The adaptive fuzzy relay scheme is proposed that combines strengths of both current and phase comparison protection criteria. The relay stabilization characteristic is adapted on-line depending on the output of the fuzzy reasoning scheme supplied with information from the phase comparison...
Celem niniejszych badań było określenie wpływu ściółkowania i nawożenia organicznego na cechy siły wzrostu dwuletnich siewek sosny oraz na występowanie roztoczy (Acari) glebowych w warunkach nawadniania. W pracy dokonano oceny udatności zaproponowanych zabiegów rewitalizacyjnych gleb szkółki za pomocą metody bioindykacyjnej. Organizmami wskaźnikowymi w tych badaniach były pospolite i bardzo liczne...
Przeprowadzone badania ujawniły, że rozwój agroturystyki musi i powinien być skoordynowany z działaniami instytucjonalnymi, które wydają się być niezbędne, by oferowana usługa miała charakter kompleksowy i profesjonalny. Bez odpowiedniego wsparcia różnych organów (władz lokalnych, stowarzyszeń agroturystycznych, Federacji i innych) ta pozarolnicza działalność gospodarcza nadal ograniczała się będzie...
Z przedstawionego materiału badawczego wynika, że usługodawcy starają się stworzyć usługę wysokiej jakości. Przejawia się to nie tylko w proponowanej ofercie atrakcji, ale również dbałości o klienta poprzez osobiste organizowanie mu pobytu. Należy pamiętać, że współczesny konsument oczekuje obok wypoczynku w miłej atmosferze, okazywania nim zainteresowania, często też fachowej porady i przede wszystkim...
In the experiment, the productivity of winter wheat grown with diversified nitrogen fertilization as a cover crop for the undersowns crop of seradella and white clover, as well as their mixture were compared. After wheat harvest, stubble crops of white mustard and fodder pea and their mixtures were sown. Field experiment was conducted in two growth seasons – 2004/2005 and 2005/2006 on Eutric Gleyic...
Przedstawiono problematykę związaną z projektowaniem cylindrycznych silosów zbożowych z cienkich blach płaskich łączonych na śruby. Zgodnie z obowiązującymi normami i zaleceniami, sztywność i wytrzymałość połączeń elementów cienkościennych należy wyznaczać doświadczalnie. Podano przykłady obliczeń i rozwiązań konstrukcyjnych niewielkich silosów i wyniki badań doświadczalnych połączeń śrubowych cienkich...
If the trip of overload branch may cause cascading tripping in corresponding section, emergency overload control should be executed to ensure the security of the transmission section and maintain its integrality and transmission capacity. A series of improvements against the conventional sensitivity algorithm are proposed, which include the advance of the integrative sensitivity, the use of equal...
Dynamic voltage stability analysis is mainly based on the time-domain solution of power system differential equations. The modeling of each power element has a great influence on the correctness and complexity of stability analyzing. It is a significant work to model appropriately for simplifying calculation and drawing out principal contradiction. Firstly, the dynamical mechanism of voltage stability...
This paper presents a new relay for the protection of power transmission systems by using the global positioning system (GPS) and the transient polarity comparison techniques, the positional polarity comparison relay. A specially designed protection relay detects the fault generated high frequency current transient signals and records the polarity of the transient signal and the time instant corresponding...
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