What are the dangers of "secondary" lightning?

"Secondary" lightning is also known as "indirect lightning strike". The so-called "indirect bombardment of lightning", is by lightning on industrial circuits or household appliances and the formation of non-direct bombardment of the discharge phenomenon. When lightning enters the earth along a lightning rod, a strong magnetic field is formed around it, which causes overvoltage in electrical devices and instrumentation power supplies. At the time of the invention of lightning rods, the people, for the "second" lightning phenomenon, do not seem to be clear. In the last 10 years, however, the damage caused by indirect lightning strikes on buildings has tripled. In the energy equivalent to the medium level of lightning bombardment, lightning rods can produce millions of volts of high voltage. If the lightning rod is not sufficiently well grounded, a number of circuit branches of lightning can form underground, which can cause the voltage of the household grid to jump to tens of thousands of volts. For ordinary household appliances, such as washing machines and refrigerators, it is already quite dangerous when the supply voltage rises to 300 volts! Like televisions, electronic computers and specialized medical equipment, as long as the overvoltage of about 10 volts, these electronic devices may be "burned out". Therefore, people should not forget such a sentence of advice: "Thunderstorms, please unplug!" Australian research lightning phenomenon experts have suggested; architects in the design of the internal layout of the building, under any circumstances, do not put the electronic computers and medical equipment installed in the building on the upper floors, unless the roof with tin cover. Because, the tin roof can make lightning-induced high-pressure, along a large area of tin quickly drain away.