The physics of power systems operation

Abstract

Summary. -The article explains the operation of power systems from the point of view of physics. Physicists imagine things, rather than in terms of impedances and circuits, in terms of fields and energy conversions. The account is concrete and simple. The use of alternating current entails the issue of reactive power. Reactive power consists of energy that oscillates between electrical and magnetic fields, it flows on top of the active power which carries the useful energy. The control of active and reactive power is essential for the power system's reliable operation. The frequency of a power system is the same everywhere. The stability of the frequency indicates that generation and demand of active power are equal, a decline in frequency indicates a lack of generation relative to the demand. Adapting the electrical power injected into the system is the way of frequency control. Because of the parasitic inductances and capacitances of overhead lines, cables, and transformers, the voltage at different locations of the power system depends on the load. The voltage is regulated by the combined action of generator excitation, transformer tap changers and series compensation in order to provide consumers with a stable voltage supply. The integration of solar cells and wind turbines into the power system poses some challenges. But the power system is able to accommodate large amounts of fluctuating renewable power generation if the right complementary measures are taken.

Semantic Web Application and Framework Development in South African Higher Education Institutions

“…In the framework, the two dotted double-edged arrows point towards the educational impact, and the SW tutoring agent root signifies the dynamic between the learners and educators/institution in the SWintegrated framework. The learner's role involves the eagerness of learners to collaborate with pedagogical technologies in an attempt to develop their knowledge and achieve their learning goals (Dotsika, 2012;Ohler, 2010). This communication/interaction can only be made attainable through personalised and adaptable educational Web 3.0 content.…”

“…As mentioned above and illustrated in Figure 3, the root representing the educational impact metric has four leaves, namely innovation/collaboration, contentdrivenness, information quality, and transformation/ sustainability (Ohler, 2010;Dotsika, 2012). These are briefly discussed below.…”