25 research outputs found
Statistical method for identification of sources of electromechanical oscillations in power systems
The use of real-time continuous dynamics monitoring often indicates dynamic behaviour
that was not anticipated by model-based studies. In such cases it can be
difficult to locate the sources of problems using conventional tools. This thesis details
the possibility of diagnosing the causes of problems related to oscillatory stability using
measurement-based data such as active power and mode decay time constant, derived
from system models. The aim of this work was to identify dynamics problems independently
of an analytical dynamic model, which should prove useful in diagnosing and
correcting dynamics problems.
New statistical techniques were applied to both dynamic models and real systems which
yielded information about the causes of the long decay time constants observed in these
systems. Wavelet transforms in conjunction with General Linear Models (GLMs) were
used to improve the statistical prediction of decay time constants derived from the
system. Logic regression was introduced as a method of establishing important interactions
of loadflow variables that contribute to poor damping.
The methodology was used in a number of case studies including the 0.62Hz Icelandic
model mode and a 0.48Hz mode from the real Australian system. The results presented
herein confirm the feasibility of this approach to the oscillation source location problem,
as combinations of loadflow variables can be identified and used to control mode
damping. These ranked combinations could be used by a system operator to provide
more comprehensive control of oscillations in comparison to current techniques
European Atlas of Natural Radiation
Natural ionizing radiation is considered as the largest contributor to the collective effective dose received by the world population. The human population is continuously exposed to ionizing radiation from several natural sources that can be classified into two broad categories: high-energy cosmic rays incident on the Earthâs atmosphere and releasing secondary radiation (cosmic contribution); and radioactive nuclides generated during the formation of the Earth and still present in the Earthâs crust (terrestrial contribution). Terrestrial radioactivity is mostly produced by the uranium and thorium radioactive families together with potassium. In most circumstances, radon, a noble gas produced in the radioactive decay of uranium, is the most important contributor to the total dose.
This Atlas aims to present the current state of knowledge of natural radioactivity, by giving general background information, and describing its various sources. This reference material is complemented by a collection of maps of Europe displaying the levels of natural radioactivity caused by different sources.
It is a compilation of contributions and reviews received from more than 80 experts in their field: they come from universities, research centres, national and European authorities and international organizations.
This Atlas provides reference material and makes harmonized datasets available to the scientific community and national competent authorities. In parallel, this Atlas may serve as a tool for the public to:
⢠familiarize itself with natural radioactivity;
⢠be informed about the levels of natural radioactivity caused by different sources;
⢠have a more balanced view of the annual dose received by the world population, to which natural radioactivity is the largest contributor;
⢠and make direct comparisons between doses from natural sources of ionizing radiation and those from man-made (artificial) ones, hence to better understand the latter.JRC.G.10-Knowledge for Nuclear Security and Safet