Overvoltage Protection

Course Description

Traveling waves. Wave equation. Reflections and refractions of traveling waves. Petersen s rule. Multiple reflections; lattice diagram. Overvoltage classification according to IEC-71-1. Temporary overvoltages; Ferranti s effect, ferroresonance, overvoltages due to faults. Switchings of unloaded transmission lines, cables, transformers and reactors. Very fast transient overvoltages in metal encapsulated substations. Classical and metal-oxide (MO) surge-arrester; working principles and protection zone. Selection of the MO surge-arresters parameters. Atmospheric overvoltages; origin and development mechanism. Llightning detection systems. Overhead transmission line lightning protection. Overvoltage protection of the switchgear, transformers and generators. Deterministical and statistical approach to the insulation coordination. Lightning protection of important objects and substations. Electro-geometrical model. Overvoltage protection of low voltage (LV) systems; protective zones, protection equipment.

General Competencies

Basic theoretical and practical knowledge about principles of overvoltage generation and propagation. Ability to implement computational procedures and protection devices for overvoltage control.

Learning Outcomes

  1. distinguish and classify overvoltages
  2. arrange causes and effects of overvoltages phenomena
  3. analyze overvoltage apperiance and necessity of overvoltage protection devices application
  4. operate with terms which defined overvoltage protection devices
  5. calculate and analyse overvoltages in simple simulation circuits
  6. demonstrate actual knowledge regarding overvoltage protection

Forms of Teaching


Lecture presentations are available on the website


Solving problems and examples regarding overvoltages and overvoltage protection

Laboratory Work

Laboratory exercises in EMTP-ATP and experiments in high voltage laboratory


According to the available literature in a specific area of overvoltage protection students prepare a seminar in the form of written material and presentation

Structural Exercises

Selection of surge arresters in high-voltage systems

Grading Method

Continuous Assessment Exam
Type Threshold Percent of Grade Threshold Percent of Grade
Laboratory Exercises 33 % 15 % 33 % 15 %
Homeworks 33 % 20 % 33 % 20 %
Mid Term Exam: Written 0 % 30 % 0 %
Final Exam: Written 0 % 20 %
Final Exam: Oral 15 %
Exam: Written 60 % 30 %
Exam: Oral 35 %

Week by Week Schedule

  1. Basic definitions and classification of overvoltages.
  2. Overvoltages on HV overhead lines.
  3. Surge arresters in stations and on lines.
  4. Surge arrester selection procedure.
  5. Electrogeometric model for overhead lines and buildings. Overvoltage protection zones.
  6. Generation and measurment of impuls curents.
  7. Mid-term exam preparation.
  8. Mid-term exam.
  9. Lightning location system in Croatia.
  10. Theoretical bese of electromagnetic transient phenomena.
  11. ElectroMagnetic Transient Program (EMTP) - Ferranty effect - Interuption of small inductive currents
  12. ElectroMagnetic Transient Program (EMTP) - Short circuit on 400 kV overhead line - Surge arrester modeling
  13. ElectroMagnetic Transient Program (EMTP) - Student practice work
  14. Presentation of students individual work
  15. Presentation of students individual work

Study Programmes

University graduate
Electrical Power Engineering (profile)
Specialization Course (3. semester)


N. Watson, J. Arrilaga (2003.), Power Systems Electromagnetic Transients Simulation, IEE
P. Hasse (2000.), Overvoltage Protection of Low Voltage Systems, IEE
M. Padelin (1987.), Zaštita od groma, Školska knjiga
(2007.), Lightning Protection Guide, Dehn


Laboratory exercises

For students


ID 86594
  Winter semester
L1 English Level
L2 e-Learning
21 Lectures
2 Exercises
7 Laboratory exercises
0 Project laboratory

Grading System

85 Excellent
75 Very Good
60 Good
50 Acceptable