ELECTRIC POWER UTILIZATION AND SAFETY

Note. In the 2026/2027 Academic Year, the Course (9 ECTS credits) will be jointly taught by Prof. Stefania Conti, the course coordinator, who will be responsible for the lecture-based teaching associated with 7 ECTS credits (7 CFU) , and Prof. Cristina Ventura, who will be responsible for exercise and laboratory activities associated with the remaining 2 ECTS credits (2 CFU).

The Course aims to provide knowledge of the structure, components, functions and analysis methods, as well as the basic design criteria, of Category I electrical distribution networks (commonly referred to as Low-Voltage, LV, networks).

The Course will therefore focus specifically on the design of LV networks in compliance with CEI (Italian Electrotechnical Committee) standards concerning Electrical Safety, with reference also to relevant international standards.

With specific reference to the expected learning outcomes, these are detailed as follows:

* Knowledge and understanding: knowledge and understanding of the structure, components and functions of LV electrical distribution networks, as well as of CEI standards concerning electrical safety.

* Applying knowledge and understanding: ability to analyse and design LV electrical installations, perform short-circuit calculations, and select and coordinate protective devices against overcurrents and indirect contact.

* Making judgements: ability to critically assess design solutions in terms of safety, reliability and compliance with applicable standards.

* Communication skills: ability to prepare and present technical reports and drawings of LV electrical installations using appropriate technical terminology and symbols.

* Learning skills: ability to independently keep up to date with developments in CEI and IEC standards and with emerging technologies for LV electrical distribution.

The teaching includes both lectures and software supported exercises aimed at putting the contents of the theoretical notions into practice and developing the related skills.

Basic knowledge of Electrotechnics, with specific reference to the laws relating to electric and electromagnetic fields, the analysis of radial and meshed electrical circuits in direct and alternating sinusoidal current, in steady state and transient regimes, as well as to the operation of Electrical Power Systems, both single-phase and three-phase systems (symmetrical and balanced or not).

Basic knowledge of the main Electrical Machines (Power Transformers, Synchronous and Asynchronous Machines and Power Electronic Converters) and their operating principles and modelling

Attendance at the Course is not mandatory but it is strongly recommended, as the Course includes, in addition to theoretical lessons, participatory numerical exercises and group activities, including technical visits.

Note. In the 2026/2027 Academic Year, the Course (9 ECTS credits) will be jointly taught by Prof. Stefania Conti, the course coordinator, who will deliver lectures corresponding to 7 ECTS credits, and Prof. Cristina Ventura, who will conduct exercise and laboratory sessions corresponding to the remaining 2 ECTS credits.

0. Presentation of the Course Syllabus and its specific areas of interest in relation to the main functions of Electric Power Systems (Generation, Transmission, Distribution, and Utilization).

1. Overview of Standards and Legislation for Electric Power Systems; Design Documentation for Electrical Installations.

2. Main definitions and classifications relating to electrical installations. Review of fundamental technical choices. The role of the neutral conductor in three-phase systems. Definition of nominal voltage to Earth and Categories 0, I, II and III. Classification of LV distribution systems.

3. Determination of the Conventional Load of electrical circuits and installations. Conventional Power and Conventional Current.

4. Constructional characteristics of electrical wiring systems: cable systems.

5. Criteria for the electrical sizing and verification of LV wiring systems. R–L line model.

6. Overcurrents: overload and short circuit.

7. Calculation of short-circuit currents in radial distribution networks.

8. Switching devices for LV installations.

9. Overcurrent protective devices: classification of different types of protection relays and fuses. Circuit breakers for LV installations.

10. Selection and installation of overcurrent protective devices in accordance with CEI Standards.

11. Selectivity criteria for overcurrent protection.

12. Electric shock: effects of electric current on the human body and current–time zones of effects of AC current on the human body. Direct and indirect contact. Definition of exposed-conductive-part and extraneous-conductive-part.

13. The role of Earth as an electrical conductor. Earth electrodes. Earth potential distribution. Earth resistance and earth potential rise. Electrical model of the human body. Body resistance and resistance of a person to Earth.

14. Touch voltage and prospective touch voltage. Indirect contact with electrical equipment connected and not connected to Earth. Voltage–time safety curve.

15. Structure of the earthing arrangement. Definition of TT, TN and IT systems.

16. Protection against indirect contact in TT systems by automatic disconnection of supply. Residual current devices (RCDs) and their operating characteristics. Selectivity between RCDs. The concepts of extraneous-conductive-parts and equipotential bonding in TT systems.

17. Protection against indirect contact in TN systems and comparison with TT systems.

18. Protection against indirect contact in IT systems.

19. Protection against indirect contact without automatic disconnection of supply.

20. Protection against direct contact.

21. Overview of the requirements for electrical installations in “Special Installations or Locations” as defined by CEI 64-8.

22. Installation of protective and switching devices in phase and neutral conductors in TT, TN and IT systems.

For reference:

1) Technical Publications and Reports written by professionals in the International Electricity Eector (in English).

2) CEI, CENELEC and IEC standards (in Italian and in English).

Required reading:

5) Teaching material provided by the professor (in Italian and in English).

Learning assessment is usually carried out by an oral exam in presence, but it might also be carried out remotely, should particular and justified conditions require it.

Relevant elements to determine the final mark will be:

- accuracy of the answers;

- completeness of the information provided;

- quality of the used technical language. 

To ensure equal opportunities and in compliance with current laws, interested students may request a personal interview in order to plan any compensatory and/or dispensatory measures based on educational objectives and specific needs. Students can also contact the reference professor for CInAP (Centro per l’integrazione Attiva e Partecipata - Servizi per le Disabilità e/o i DSA) within the Department.

Examples of typical questions and/or exercises:

* Explain the role of the neutral conductor in three-phase systems.

* Describe the structure of a singl-phase LV electrical distribution system.

* Calculate the design current of an electrical circuit from the given load and nominal voltage; size the wiring system in accordance with CEI standards.

* Define the characteristics of the protective devices required to protect a circuit against overload and short circuit.

* Calculate analytically the maximum and minimum short-circuit currents in a three-phase LV line.

* Explain the differences between TT, TN and IT systems, with particular reference to protection against indirect contact.

* Explain how to use RCDs as a protection against direct contacts according to CEI 64-8 standard.

* Describe the phenomenon of electric shock and the current–time zones of effects of electric current on the human body.

* Explain how to design an earthing system and calculate the total earth resistance and total earth potential rise.