Impedance Method Used To Calculate Initial Switching Currents in Transmission Networks and Generator Real Power

Switching-on of transmission network elements can bring about high inrush currents in the network elements (lines and transformers) as well as sudden changes in real power of generating units. In order to reduce those disadvantageous effects in modern power systems switching operations are controlled by protection devices referred to as synchro-check. Optimal setting of the synchro-check parameters requires the application of adequate criteria and an efficient method for calculating current changes in lines and generators that result from switching operations. This article proposes a new calculation method based on a nodal impedance matrix. Such a matrix is commonly used for short-circuit analyses. The advantage of the proposed method is that a short-circuit software with an adequate extension can be also applied to the analysis of switching operations

Potential source rocks in the Ropianka Formation of the Magura Nappe (Outer Carpathians, Poland) – geochemical and foraminiferal case study

To optimize exploration for new hydrocarbon accumulations in the Polish Outer Carpathians, it is necessary to concentrate attention on identification of hydrocarbon accumulations of the “shale-gas” type. Results of recently completed analysis suggested new such possible targets in the Magura Basin, preserved in the Outer Carpathian Magura Nappe. Analysis of the preliminary results of paleoenvironmental and geochemical studies of these shales is the subject of this paper. Micropaleontological and geochemical study was conducted on the 300 m thick Świątkowa Member, the uppermost part of the Ropianka Formation located in the external, northernmost Siary Zone. This member is composed of thin- and medium-bedded sandstones interbedded by green, brown, black and dark-gray shales. Poor and changeable oxygenation is reflected in the composition of foraminiferal assemblages. A negative correlation between the TOC content and numbers and diversity of foraminifera is observed. The paleogeographic position and paleoenvironment assessment indicates that the Siary Zone fulfills certain conditions for organic productivity and preservation during the deposition of the Ropianka Formation

The late Vistulian and Holocene evolution of Jezioro Lake : a record of environmental change in southern Poland found in deposits and landforms

Jezioro Lake is the only natural lake in southern Poland outside mountainous areas to have existed continuously since the Pleistocene. The record of environmental change in the Late Vistulian (Weichselian) and Holocene is preserved in the deposits and landforms around the lake. This paper presents the results of paleogeographical and paleoecological research that emabled us to reconstruct the history of the Jezioro Lake. At the end of the Vistulian period, the outlet of the lake was blocked by a parabolic dune moving in from the west. Limnic sedimentation was evident in the sediment core at all levels from the Holocene, with remains of Cladocera, Chironomidae larvae, and aquatic plants. The lake did not disappear at that time, although its area decreased by a factor of 12 by the end of the period. Paleobotanical research permitted the reconstruction of sequences of plant communities and changes in nutrient status and water level. An initial oligotrophic lake, as indicated by the presence of Isoe¨tes lacustris L., changed to a eutrophic lake, as indicated by the presence of Potamogeton natans L. and Nuphar sp., then the lake progressed to the present-day dystrophic lake that is surrounded by a swamp. The profile of organic deposits contains a record of environmental change at least since the Younger Dryas in southern Poland

Automatic Detection of Gaps in Availability of Authoritative Online Content

This disclosure describes techniques to measure authority content gap (ACG), which represents the (lack of) authoritativeness in online content related to individual topics. The ACG metric is defined for various verticals, e.g., health, government services, legal, etc., and can be specific to region, country, language, or time period. The ACG is refreshed periodically, and it can be used in combination with other metrics relating to a content publisher. The ACG is a useful measure in various contexts, e.g., when an unpopular or obscure topic achieves sudden popularity, or when a new topic emerges. The ACG for a topic can indicate when authoritative content about such topics is unavailable and can be utilized to ameliorate the situation, e.g., by alerting content providers about the content gap

Selectivity of power system protections at power swings in power system

The paper discusses out-of-step protection systems such as: generator pole slip protections, out of step tripping protections, distance protections of step-up transformer, distance protections of transmission lines and transformers, power swing blocking, and special out-of-step protection. It is shown that all these protections make up a protection system, to which a setting concept uniform for the entire power system has to be applied. If a power system is inappropriately equipped with these protections, or their settings are inappropriate, they may operate unselectively, thus contributing to the development of power system blackouts. In the paper the concepts for a real power system are given for the two stages: target stage fully compliant with selectivity criteria, and transitional stage between the current and target stages

WAMS – based Control of Phase Angle Regulator Installed in Tie-lines of Interconnected Power System

This paper addresses the state-variable stabilising control of the power system using such series FACTS devices as TCPAR installed in the tie-line connecting control areas in an interconnected power system. This stabilising control is activated in the transient state and is supplementary with respect to the main steady-state control designed for power flow regulation. Stabilising control laws, proposed in this paper, have been derived for a linear multi-machine system model using the direct Lyapunov method with the aim of maximising the rate of energy dissipation during power swings and therefore maximising their damping. The proposed control strategy is executed by a multi-loop controller with frequency deviations in all control areas used as the input signals. Validity of the proposed state-variable control has been confi rmed by modal analysis and by computer simulation for a multi-machine test system

Computation method for analysis of sliding faults in power systems

Short-circuit analysis is conducted based on the nodal impedance matrix, which is the inversion of the nodal admittance matrix. If analysis is conducted for sliding faults, then for each fault location four elements of the nodal admittance matrix are subject to changes and the calculation of the admittance matrix inversion needs to be repeated many times. For large-scale networks such an approach is time consuming and unsatisfactory. This paper proves that for each new fault location a new impedance matrix can be found without recalculation of the matrix inversion. It can be found by a simple extension of the initial nodal impedance matrix calculated once for the input model of the network. This paper derives formulas suitable for such an extension and presents a flowchart of the computational method. Numerical tests performed for a test power system confirm the validity and usefulness of the proposed method