34663 - Electrical Systems M

Learning outcomes

The course provides an introduction to electric power transmission and distribution systems.

Course contents

The course is divided in the following two modules.

A module of 60 hours (Prof. Alberto Borghetti - oral exam) covers the topics of theory of power transmission lines and switching devices and it provides and introduction to protective relaying: equivalent circuit of a two-wire line, external inductance, internal inductance, inductance of a conductor placed above to a  conductor plan and method of images, introduction to the skin effect, complex depth, skin effect in  circular conductors, matrices of impedances, proximity effect, forces on conductors, capacitance of a two-wire line above ground, corona effect and bundle conductors, inductance of a line with bundle conductors, characteristic impedance and propagation constant of a two-wire line, direct and reflected waves, solution of the line equations, reflection coefficients, equivalent circuits of a line, multi-conductor lines, modal decomposition, balanced lines and symmetrical sequences transformation, overhead line with transposed conductors, line sag and tension analysis and effect of change with temperature, insulators, electric field distribution in the insulator chain, cables, voltage levels and designation of cables, grounding of the cable shields, cable constants, thermal behavior of cables and equivalent electrical circuit, post fault adiabatic regime, Joule integral, voltage drop in a short line, criteria for selecting the section of cable conductors, the electric arc, interruption of alternating currents, transient recovery voltages, interruption of small inductive and capacitance currents, different types of circuit breakers and disconnectors, fuses, protections against short circuits, connection of the neutral to ground.

The second module of 30 hours (Prof. Fabio Napolitano - written exam) covers electrical safety and it provides and introduction to the main topics of electrical design at low and medium voltage: physiological effects of electric current, safety current-time curves, functions of groundings, earth resistance, touch and step voltages, earth resistance, equipment with double insulation, masses, direct and indirect contacts, main and supplementary equipotential protection by electrical separation, low voltage systems, restricted conductive areas, differential relays, protection against indirect contact in medium and high voltage systems, protection against indirect contact in low voltage systems, calculation of short-circuit currents at the terminals of three-phase distribution transformers, unbalanced faults, transient short-circuit current, the definition of the plant layout, sizing of electrical conductors in medium and low voltage networks, selection of the protection as well as coordination, power factor correction systems, regulatory requirements and standards.

Readings/Bibliography

Lecture notes are available at the web site  http://campus.cib.unibo.it . Several books and standards on the course topics are also available at the library.

Assessment methods

The examination at the end of the course aims at assessing the achievement of learning objectives. The exam is composed by two tests: 
- written exam on safety standards and analysis of low and medium voltage distribution networks; 
- oral exam on the theory of transmission lines, switching devices and protective relaying.  The final grade is defined on the basis of the positive grades of the written test and the spoken test. (exam schedules at  https://almaesami.unibo.it ).

Office hours

See the website of Alberto Borghetti

See the website of Fabio Napolitano