Course detail

Diagnostics and Electrical Equipments Protections

FEKT-MPA-DJZAcad. year: 2023/2024

Faults and protections against overcurrents in electrical equipments. Protective devices and their characteristics. Protection of cables and wires aganist overloads and short circuits. LV motors and generators protection. Protectin devices for transformers, capacitancies, batteries etc. Usage of switchgears in switgear assemblies. Protection of semiconductors. Overvoltage protection devices. Protection against electric shock, residual current devices.

Language of instruction


Number of ECTS credits


Mode of study

Not applicable.

Offered to foreign students

Of all faculties

Entry knowledge

The subject knowledge on the Bachelor´s degree level is requested.
Requested knowledge:
- to solve electrical circuits by the method of circuit simplification and nodes potentials
- knowledge of electrodynamic forces effects and calculation
- knowledge of thermal effects of electric currents in steady state and during transient period
- calculation of short-circuit currents in LV networks
- classification of electrical switching devices based on the ability to switch various currents
- phonemena during motor start
- function of a transformer
- knowledge of regulation 50/1978 Sb.

Rules for evaluation and completion of the course

exam - 100 points

The content and forms of instruction in the evaluated course are specified by a regulation issued by the lecturer responsible for the course and updated for every academic year.


Students will understand characteristics of electrical protective devices and their usage for protection of individual types of electrical devices. In the event that a student enrolls in this elective course, the credits earned upon successful completion will be credited to the category of required courses in lieu of the MPC-DJZ course.
Students can describe:
- principal of function of various protective devices
- principals of protection against overcurrents for individual kinds of devices
- principals of selectivity determination
- principals of protection against electric shock
- principals of overvoltage protection

Students can explain
- meaning of parameters of protective devices
- phonemena influencing design of protection for electric devices
- kinds of selectivity between protective devices
- principals of individual protective provisions for protective measure automatic disconnection of supply
- overvoltage origin and protection against it

Students are able to design
- cables protection against overload and short circuit
- protection of motors and inlets to them
- protection of transformers
- protection of semiconductors
- protection of capacitive bateries
- selectively connected protection devices in series
- electric circuit from the automatic disconnection of supply point of view
- individual levels of overvoltage protection

Students are able to analyse
- effects influencing protection of electric devices
- effetcts of short-circuit currents
- appropriate usage of protective devices

Students are able to judge
- correctness of overcurrent protection of electric devices
- selectivity between protective devices
- protection of surge arrestors
- fulfillment of conditions for protective measure automatic disconnection of supply

Students are able to compose
- report concerning protection of electric devices
- protocol on short circuit calculation
- protokol on measurement of important parameters of protective devices

Study aids

Not applicable.

Prerequisites and corequisites

Not applicable.

Basic literature

Brittian L.W.: Electrical Circuit Breakers, Fuses, Protective Relays, and More (EN)
Ragunath Ram: Electrical Protection Systems & Units: Protection Devices Guide (EN)
NCCER: Circuit Breakers and Fuses TG, ISBN: 9780132661393 (EN)
Dunning J.: The Fundamentals of Circuit Breaker & Protection Maintenance, ISBN: 9781519258410 (EN)

Recommended reading

Flurscheim C.H.: Power Circuit Breaker Theory and Design (Energy Engineering), ISBN: 978-0906048702 (EN)


Classification of course in study plans

  • Programme MPC-SVE Master's, any year of study, winter semester, compulsory-optional
  • Programme MPA-EEN Master's, 2. year of study, winter semester, compulsory-optional

Type of course unit



39 hours, optionally

Teacher / Lecturer


Purpose of electrical equipment protections.
Failures and types of faults
Protection devices basic characteristics
Fuses, characterics and applications
Short-circuit currents evaluation.
Protection of lines.
Protection of electric motors.
Protection of transformers.
Protection of semiconductors.
Computarized protections
Selectivity of protection devices
Protection against electric shock
Protections against overvoltages

Exercise in computer lab

4 hours, optionally

Teacher / Lecturer


Choice of protection device for electric motor and el. network
PC aided selectivity design.

Laboratory exercise

22 hours, optionally

Teacher / Lecturer


Electrical equipment type and production measurements and tests.
Electrical switch voltage test.
Losses of a fuse.
Test of el. device switching time.
Thermal relay characteristic measurements.
Practical test of sectivity in laboratory circuits
Connection and test of overvoltage protection <BOD<Test of microprocessor protection
Impedance loop calculation and meassurement
Residual current device testing
SPACOM protection using and simulation