Selection of Protection Scheme against Lightning Impulse Waves Based on Chaos Theory for 500kV GIS Substation

Aimed at the overvoltage trouble of electric equipments in 500 kV GIS substation caused by lightning strikes to overhead line, four protection solutions were proposed. Through ATP simulation, the protection margins and economy of the protective devices such as transformer, reactor, CVT and GIS-inlet were estimated. It is concluded that installation of a set of outdoor type surge arrester at line inlet and a set of indoor type one at main transformers may effectively reduce the lightning overvoltage based on chaos fractal theory, fractal dimension and Kolmogorov entropy of voltage wave at transformer were calculated and compared, and the positive correlation between the protection margin and Kolmogorov entropy was proved. It is proposed that protection solution may be determined using chaos characteristics of voltage wave, it is satisfactory when potection point P is not less than the reference point Pi, namely, PgesP_i.