Essay upon Power System Stability

SCYR 2010 - 10th Scientific Convention of Youthful Researchers – FEI TU of Košice

Stability of Power Program (May 2011)



Vladimír KRIŠTOF, 2Stanislav KUŠNÍR, 3Matúš KATIN

Dept. of Electric Power Executive, FEI TU of Košice, Slovak Republic Dept. of electrical Power Engineering, FEI TU of Košice, Slovak Republic 3 Dept. of Electric Power Engineering, FEI TU of Košice, Slovak Republic two 1

vladimir. [email protected] sk, 2stanislav. [email protected] sk, 3matus. [email protected] sk change rapidly, but the mechanical power in to the machine is actually slow to change. Because of this big difference in speed of response, there exists a non permanent difference in the balance of power. This power unbalance causes a difference in torque applied to the shaft, which in turn causes it to accelerate or decelerate, with regards to the direction with the unbalance. While the disc changes rate, the relative rotor perspective changes. Fig. 2 shows the relationship involving the rotor (torque) angle δ, the stator magnetomotive force (MMF) F1, and the brake disc MMF F2. The rpm angle δ is the position between the brake disc MMF F2 and the resultant of the vector addition in the rotor and stator MMFs R, because shown in Fig. a couple of

Abstract— Due to increase of electrical power requirements, power systems are bigger and more complicated, and the dependence of people about electricity boosts. Outages in electric supply have an raising social and economic influence. Therefore it is essential to minimize the result of disorders that come up in the electricity system in order to have lowest impact on the reliable and safe supply of electrical energy. Stability of power product is one of the most essential area of electric power system procedure. Loss of steadiness (loss of synchronism) can result in outages of transmission lines, loss of loads, cascading failures, and eventually to black-out. This kind of paper discusses power-system instability and the significance of fast fault-clearing performance to help in dependable production of power.

Keywords—power system, steady-state stability, transient stability, fault-clearing time

I. INTRODUCTION Power system balance has been recognized as an important difficulty for secure system procedure since the twenties [3], [4]. Many main blackouts caused by power program instability possess illustrated the importance of this trend [3]. The term stability of the electricity system is linked with transient tendency associated with changes in generator disc angle, within frequency and voltage. Presented the wide range of issues there may be need for classification of electrical power system stability according to Fig. 3. [5] This information deals mainly with steady-state and transitive stability. II. BASIS FOR STEADY-STATE STABLENESS In an interconnected power system, the rotors of each synchronous machine inside the system rotate at the same typical electrical rate. The power shipped by the generator to the power system is corresponding to the mechanised power applied by the perfect mover, neglecting losses. During steady-state operation, the electricity out balances the mechanical power in. The physical power input to the shaft from the excellent mover may be the product of torque and acceleration (P M = Big t M ω). The physical torque is in the direction of rotation. Any torque is usually applied to the shaft by the generator and it is in a path that is opposite of the rotation, as displayed in Fig. 1 . If the system is disturbed due to a fault or when the weight is transformed quickly, the electrical power from the machine improvements. The electricity out of the machine can


Fig. 1 . Physical and power torques placed on the the whole length [2].

Fig. 2 . Stator, disc, and resultant MMFs and torque viewpoint [2].

SCYR 2010 - tenth Scientific Seminar of Youthful Researchers – FEI TU of Košice

Fig. a few. Classification of power system stability relating to IEEE and CIGRE [3, 7]

Fig. 5 shows a circuit manifestation of a synchronous generator connected through a transmission system for an infinite coach. The synchronous machine is definitely modeled by simply an...

Referrals: Krištof, Sixth is v.: Riadenie SERA v krízových situáciach. Minimová práca. Košice: Technická univerzita v Košiciach, Fakulta elektrotechniky a informatiky, 2010. [2] Basler, M. J. Schaefer, R. C.: Understanding Power system balance. In: Market applications, IEEE Transactions about. March 08. ISSN: 0093-9994 [3] Kundur, P. Paserba, J. - Ajjarapu, Versus. Andersson, G. - Bose, A. Canizares, C. Hatziargyrou, N. Mountain, D. -- Stankovic, A. - Taylor, C. Vehicle Custem, Big t. Vittal, Versus.: Definiton and clasification of power system stability. In: Power Systems, IEEE Deals on. August 2004. ISSN: 0885-8950 [4] Krištof, Versus. Kušnír, S. - Hlubeň, D. -- Kolcun, Meters.: Modeling of transient tendency in PSLF. In: Electricity engineering 2010: international scientific and technological conference: 14-16. 10. 2010, Varna, Getaway. - Apuokas: TU, 2010 P. 186-190. - ISBN 978-954-20-0497-4 [5] Mešter, Meters.: Analýza hraničných podmienok balance elektrizačnej sústavy pri rôznych typoch skratov. Dizertačná práca. Košice: Technická univerzita sixth is v Košiciach, Fakulta elektrotechniky a informatiky, 2004. [6] CIGRE: Advanced Perspective stability handles. CIGRÉ Technological Brochure. International Conference in Large Hollywood Electric Systems 1999. [7] Mešter, Meters. Hvizdoš, Meters. Rusnák, T. Szathmáry, S. Vargončík, Meters: Stabilita elektrizačnej sústavy. Equilibria 2006. ISBN 80–969224– 9-1 [8] Prabha, K.: Electricity System Stableness and Control. United States of America. 1993. 0-07-035958-X [9] Machowski, L. − Bialek, J. Watts. − Bumby, R. J.: Power program dynamics and stability. England, 1997. 484 s, 978-0-471-95643-3 [10] Yorino, N. Priyadi, A. Kakui, H. Takeshita, M.: A new method obtaining critical eradicating time for transitive stability. In: Power Devices, IEEE deals on. September 2010. ISSN 0885-8950. [1]

Fig. almost 8. Influence of fault cleaning time: a) slow wrong doing clearing period b) quickly fault eradicating time

Power-system stability depends on the clearing moment for a wrong doing on the indication system. Contrasting the two cases in Fig. 8 shows this point. Inside the example of slower fault clearing (a), the time duration of the fault enables the disc to increase the speed of so far over the curve of PE which the decelerating torque comes directly to the limit of maintaining the rotor in synchronism. The short fault-clearing time (b) halts the velocity of the brake disc much sooner, assuring that sufficient synchronizing torque can be bought to recover using a large security margin. This effect may be the demand placed on protection technical engineers to install the fastest available relaying products to protect the transmission system.

IV. BOTTOM LINE Due to the elevating electricity intake and economic and time intensive construction of recent power lines, existing networks are controlled more in the limits with their possibilities and they are just an best of steadiness of electric power system. It is therefore necessary pay close attention to power system stability and control.


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