Reliable protection of electronics against lightning: some practical applications

The classical lightning conductor, which must prevent fire, has to have a sufficiently small resistance. An analogous condition can be formulated for the new challenge: the protection of sensitive electronics against lightning. In this case, the so-called transfer impedance, which gives the interference voltages across a sensitive input per ampere lightning current, must be made small. The arguments for this approach are described. A theoretical description is available and practical experience has been built up over the years, also in high-voltage (HV) research and in power engineering measurements in the field. This approach was used to greatly improve the lightning protection of several installations: a marine radio station, the peripheral equipment of a nuclear power plant, and an electronic siren for a nationwide public warning system. Detailed investigations were requested by our contract partners, together with suggestions for economically acceptable improvements that could be carried out in reasonable time. Later, the correctness of the renovations had to be demonstrated. In the validation measurements, we injected currents into the installation or into relevant parts thereof. The current waveform was chosen fast enough so that inductive effects determined the current distribution. At present, lightning position and tracking system (LPATS) data on lightning strikes near the marine radio station and the nuclear power plant are available to verify the effectiveness of the protection. After our improvements no more damage was reported.