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2 Zeszyty Naukowe. Elektryka / Politechnika Opolska

2 2005

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Resonance overvoltages in electric power networks

Belán A., Eleschová Ž., Smola M.

Zeszyty Naukowe. Elektryka / Politechnika Opolska

2005

Vol. 299, z. 55

33-39

Resonance exists in circuits composed of inductance and capacitance, possibly resistance. Resonance can cause big overvoltages in power systems. Many resonance circuits, that are present in practice, include induction coils with iron core which that induction is nonlinear. These resonance events are called ferroresonance. In this paper are included measured curves of various variables in case of ferroresonance in auxiliary's circuits of power plant. This paper also includes theoretical analysis of ferroresonance overvoltages on models of electric circuits in EMTP ATP.

Power lines protection by digital relays

Smola M., Belán A., Eleschová Ž.

Zeszyty Naukowe. Elektryka / Politechnika Opolska

2005

Vol. 299, z. 55

203-208

This paper shows possible options in protection of power lines by digital relays, that are used in Slovak power system. It shows demands given by STN and possible protection schemes. Electric power lines are still the only media for electric power transportation from power plants to customers and they can be, notwithstanding thoroughgoing operating, liable to various mechanical or electrical failures. Relays can not prevent failures, they just minimize their consequences. This paper shows just a part of power lines protection area, aimed for protection schemes and relays used in Slovak power system. Big systems outages that last year affects power systems in Italy and United States shows, that question of protection coordination and correct choose of protection scheme are significant demands for trouble free operating of power systems.