Kordi - Comnurnicalion Group Amirkabir University I. R.Iran
Moini - Comnurnicalion Group Amirkabir University I. R.Iran
Vahidi - Power System Group Amirkabir University I. R.Iran
MA hedi - Power System Group Amirkabir University I. R.Iran

In this paper an attempt has keen made to introduce a method for evaluation of induced overvoltages caused by nuclear electromagnetic pulse (NEMP) in overhead lines. NEMP occurs in space in high altitude, due to nuclear explosion in space. The paper also compares the induced overvoltage caused by NEMP, with overvoltage produced by lightning electromagnetic pulse (LEMP). In LEMP analysis, lightning is a local phenomena, therefore the performance of transmission line can he examined conveniently, using suitable model for lightning stroke channel, and applying transmission line theory. However NEMP covers large area simultaneously, and has specific characteristic. So it is impossible to utilize transmission line theory similar to LEMP analysis. In this paper direct solution of Maxwell's equations have been used in time domain, using electric field integral equation (EFIE), for evaluation of induced voltage, and current in any point of overhead line, due to NEMP. The results presented in this article belong to 33 Kv overhead distribution line. With comparing the LEMP and NEMP results, it is found out that the overvoltage protective device (arresters), installed at the receiving or sending ends of transmission line may protect the line against LEMP however it may fail to respond against NEMP.

Nncleur Electromangnetic Pulse (NEMP), Lightning, Electromagnetic Pulse (LEMP), Lightning Induced voltage (LIV), Nuclear Induced voltage (NIV), Over Head Line (OHL)