Electrical and Electronics

 Cascading a number of single identical units makes transportation, production and erection simpler.  The cascading principle is illustrated with the basic scheme shown in .3 below in which it can be seen that output of a stage transformer becomes input for the next stage. Fig 24.3 Three Transformers in cascade

Utility-scale and small scale wind and solar power installations along with electric vehicle charging stations, and other active sources of energy are increasing at the medium and lower voltage levels in the distribution grid. This situation required a better understanding of the impact of high penetration of weather-dependent renewable energy sources on the operating conditions of the distribution network at both medium and low voltage levels. Despite the need, a multi-voltage level distribution network model, based on real network data and weather-dependent renewable generation data, has not been presented for distribution grid studies. This paper presents a comprehensive multi-voltage level active distribution network model based on real network data along with load and generation time-series for about a year. The network topology is modelled based on geographical data for various rural, semi-urban, and urban locations. The distribution network is embodied with a large share of r...

Accurately fitting rational functions to the frequency response of characteristic impedance and characteristic admittance is very crucial for frequency dependent modeling of transmission lines. Vector fitting is a most popular method for fitting rational functions to the frequency dependent characteristic impedance of transmission line. An R-C equivalent circuit will then be obtained from rational functions to simulate transmission line using Marti's model. An intuitive single step method is proposed in this paper to directly fit an equivalent circuit to the characteristic impedance. A close enough fitting is achieved with lesser number of poles & zeros using the proposed method. This is found to reduce the simulation time drastically by 89.84%.

The increased penetration of wind power plants (WPPs) in distribution networks challenges the distribution system operators (DSOs) to improve and optimize networks’ operation. A higher amount of local power production translates to more losses in the network. This paper proposes a deterministic optimization methodology to minimize the losses in distribution networks with WPPs, by exploiting WPPs’ capability to control reactive power in coordination with the on-load tap changers from the MV/HV transformer, avoiding the need for network reinforcements. The principal objective is to optimize the reactive power flow in the network. Measurements from a real distribution network with a large share of controllable WPPs under varying wind and load conditions are used for the study. The benefits and the challenges of the optimization methodology are assessed and discussed with respect to active power losses, voltage profile and reactive power. The results show that with reactive power support f...

This paper presents two methods for load angle determination for salient-pole synchronous generator. The first method uses optical encoder to detect the rotor position. In some cases the end of the rotor shaft is not free to be used and mounting of an encoder is impossible. Therefore, the second method proposes estimation of the load angle based on the measured electrical values that have been already used in excitation control system of the synchronous generator. Estimation method uses corresponding voltage-current vector diagram and parameters of the synchronous generator, transformer and transmission lines. Both methods were experimentally verified on the digital control system and synchronous generator connected to power system. The estimation and measured results were compared. The accuracy of load angle estimation method depends on voltage and current measurement accuracy as well as generator, transformer and transmission line parameter accuracy. The estimation method gives satisfactory accuracy for load angles less than 120º el. Thus, it can be applied in excitation control system to provide stable work of synchronous generator in under-excitation operating area.

Power System Operation Corporation Limited (POSOCO) (POSOCO is a wholly owned subsidiary Abstract—This paper discusses about SIPS for Southern grid in India which involves the identification and ranking of the most severe contingencies of grid elements in the network which may affect the grid if they go out of the system at any given operating condition or time of day. In addition to this the project works towards the implementation of dynamic system which will keep updating itself with the best possible SPS action to be taken in case of the contingency of a critical grid element. This dynamic system is finally modelled into a user interface program which will accomplish the above stated tasks. Presently the application is user driven and is being developed in open loop mode. The SIPS portion which activates the SPS action and sends command to the field is in designing stage.

Information propagation within the blogosphere is of much importance in implementing policies, marketing research, launching new products, and other applications. In this paper, we take a microscopic view of the information propagation pattern in blogosphere by investigating blog cascade affinity. A blog cascade is a group of posts linked together discussing about the same topic, and cascade affinity refers to the phenomenon of a blog's inclination to join a specific cascade. We identify and analyze an array of features that may affect a blogger's cascade joining behavior and utilize these features to predict cascade affinity of blogs. Evaluated on a real dataset consisting of 873,496 posts, our svm-based prediction achieved accuracy of 0.723 measured by 1. Our experiments also showed that among all features identified, the number of friends was the most important factor affecting bloggers' inclination to join cascades.