# Power System Disturbances

## Subject description

Normal and  emergency conditions in electric power systems (EPS), current and voltage stresses in EPS, significance of current stresses determination in EPS for dimensioning process as well as earth and phase overcurrent protection coordination, physical background of phenomena during phase-to-phase and earth faults, phase-to-phase and earth-fault currents calculation by applying symmetrical components approach, calculation of characteristic fault parameters according to appropriate standards, principles and methods for phase-to-phase and earth-fault current calculation applying computer software tools, electrical conductor interruption, methods and reasons for neutral-point earthing, impact of neutral earthing on earth-fault currents and switching overvoltages in EPS, basic principles of fault currents switching and description of physical conditions in switching devices during fault current switching.

## Objectives and competences

The objective of the course on Power System Disturbances is to submit understanding the physical background of phenomena leading to appearance of overvoltages and current overloading in EPS (line-to-line faults, earth-faults). A student learns the importance of knowing fault- and earth-current parameters for dimensioning process of EPS elements and setting-up overcurrent protection, further learns the methods of fault calculation and meets the standards in this field. In terms of behaviour of the system in case of disturbances, he will understand the ways and methods of an EPS neutral point grounding as well basic methods and physical principles for elimination of EPS elements that represent a source of system disturbances.

The knowledge acquired is fundamental in planning elements and parts of an EPS as well as for understanding of protection system and a protection coordination.

## Teaching and learning methods

Lectures and laboratory practice

## Expected study results

After successful completion of the course, students should be able to:

• know the causes of short and earth faults,
• use  calculation methods for phaseto-phase and earth-fault currents,
• analyse lineto-line and earth-fault currents calculation results in dimensioning process of EPS elements and overcurrent protection coordination,
• knowing methods for restraining/limiting lineto-line and earth-fault currents and and select appropriate devices,
•  analysing EPS parameters influencing faultcurrent level,
• know response of generators to a fault and distinguish between responses in different types of excitation systems.

## Basic sources and literature

1. Roeper, Richard: Kratkostični tokovi v trifaznih omrežjih :časovni potek in izračun veličin, Ljubljana : Fakulteta za elektrotehniko, 1987
2. International standard IEC 60909: Short-circuit currents in three-phase a.c. systems
3. Papič, P. Žunko: Elektroenergetska tehnika I, Založba FE in FRI, 2005.
4. Das, J. C.: Power system analysis : short-circuit load flow and harmonics, New York : Marcel Dekker, cop. 2002.

## Stay up to date

University of Ljubljana, Faculty of Electrical Engineering Tržaška cesta 25, 1000 Ljubljana