Electromagnetic pulse protection works by shielding or hardening sensitive electronics from interacting with the electromagnetic field created in an EMP. Shielding takes the form of conductive materials that enclose a protected device or critical components. A hardened electronic system, conversely, includes internal engineered components such as breakers, absorbers and a general design that can withstand higher electromagnetic fields.
An electromagnetic pulse is formed from natural sources such as electrostatic discharge, lightning strikes and meteoroids detonating in the Earth's atmosphere. These events typically require proximity to unshielded electronics to cause damage. Geomagnetic storms, which are formed from the interaction of a sufficiently powerful solar flare with the planet's magnetic field, can create EMP-like effects by inducing excess current, potentially destroying unprotected systems.
Man-made EMPs can come from nuclear and non-nuclear sources. Detonation of a nuclear weapon causes a nuclear electromagnetic pulse that affects electronics up to hundreds or thousands of miles away. In 1962, a 1.4 megaton nuclear weapon tested 900 miles west of Hawaii created a NEMP of sufficient magnitude to cause radio and telephone blackouts and streetlight overloads on the islands.
Non-nuclear forms of man-made electromagnetic pulses vary by magnitude and severity. At the damaging end of the range, power system surges and non-nuclear EMP weapons can damage or degrade unprotected electronics. Minor and localized EMPs are the result of electronic circuit switching, electric motor operation or internal combustion engine ignition.