Outline Introduction Surges on Transmission Lines Travelling wave at the end of Transmission lines Attenuation of Travelling wave Bewley-Lattice Diagram 2
Objectives • The objective of Studying Transient Analysis in power system helps: ➢ To select an appropriate insulation levels (insulation types) for power system equipments & ➢ To select an appropriate surge protective devices for power system equipments (with appropriate timing). 3
1. Transient (Surge) in power system ❑ Transient (Surge) are temporary rise in voltage and current on an electrical circuit due to switching action, Outage of line, outage of generator, outage of load, faults or lightning in power system. ❑ Lighting strike are the most common causes of transmission line transients. ❑ As a result of transient the voltage magnitude will rise beyond tolerable limits.
Cont. • Transient may results damage to power system devices like transformers… • But, Due to resistance of transmission line, travelling waves are attenuated and die out after few reflections. • The inductance of transformer at generating station is also help in preventing the surge voltage (V) from entering to generator winding. 5