29246 - Electrical Plants T

Learning outcomes

The aim of the course is to provide the theoretical and practical background concerning the operation and design of distribution power systems (medium and low voltage).

Course contents

Introduction
Structure of distribution power networks with particular reference to the medium and low voltage infrastructures. 

Components
Medium and low voltage lines: AC transmission line equations, two-port representation, parameters and equivalent circuits, thermal effects related to the current flow and Joule integral, cable and lines ampacity, short-circuit and overload behavior, specific characteristics of medium and low voltage lines. Breakers and other medium and low voltage maneuver apparatuses: arc phenomenology and current interruption principles, electromagnetic transients associated to the inception and interruption of the arc, medium and low voltage breakers, breakers characteristics. Protection relays: types and operation principles, fuses, relay coordination. General aspects on UPS, local generation and storage systems with particular reference to electrochemical storage (batteries). Medium and low voltage switchgear. 

Short circuit current calculation
Symmetrical components.
Symmetrical components equivalent circuits of transformers, lines, synchronous machines etc.
Short circuit current calculation in distribution networks.
Asynchronous machines contribution.
Mechanical forces associated to the short circuit occurrence.

Distribution networks
Typical schemes of medium and low voltage networks.
Station configuration.
Neutral grounding.
Protection schemes and relays adopted in medium voltage networks. 

Safety
Electrical current and human body.
Grounding systems. TT, TN and IT low voltage distribution systems.
Safety in medium voltage distribution networks. 

Design principles of distribution networks
Design layout.
Sizing criteria of medium /low voltage lines and relays coordination.
Relay coordination verification with reference to the short circuit currents.
Reactive power compensation systems.
National and international standards.

Laboratory activities
Symmetrical component impedance measurements of three-phase power transformer.
Measurement and simulation of three-phase power transformer energization transie.
Computer simulation of the most important electromagnetic transients in power distribution networks.
Computer aid procedures for the design of power distribution networks.

Readings/Bibliography

A. Paolucci, Lezioni di impianti elettrici, Cluep, Padova, 1997.

R. Marin, M. Valtorta, Trasmissione ed interconnessione – Introduzione all'analisi dei sistemi elettrici di potenza, CEDAM, Padova.

D. Zanobetti, M. Pezzi, Lezioni di impianti elettrici, CLUEB, Bologna, 1981.

J. C. Das, Power system Analysis, M. Dekker Inc., New York, 2002.

G. Pratesi, Le protezioni dei sistemi elettrici di potenza, Edizioni CUSL, Milano, 1999.

V. Carrescia, Fondamenti di Sicurezza elettrica, Torino: TNE, 1999.

Norme e Guide CEI.

Teaching methods

Standard lectures.
Laboratory activities (computer and experimental).
Technical visits.

Assessment methods

The exam is composed by the two subsequent tests:
- written exam about numerical calculation on distribution networks;
- oral exam.

Teaching tools

The course includes the following specific laboratory activities:
- experimental characterization of the main distribution network components;
- experimental analysis of the most important electromagnetic transients in power distribution networks;
- computer simulation of the steady-state and transient behavior of power distribution networks.

Office hours

See the website of Mario Paolone