Here are a few facts on EMP: It doesn’t kill people, it the blast that does that…BUT EMP is "line of sight’ hence the blast take place at higher altitudes and what it does is knock out electrical ‘stuff’. Mostly stuff that is connected to the grid or running may possibly be affected. Its employment would be over major cities such as NYC etc due to the concentration of electrical devices. Further from the city and from the sight level of the blast the less the impact.
Things like spike arrestors etc can offer up some protection and other things such as cars etc which are very well built systems and able to absorb eratic electrical loads generally do much better. Many computers may not work so well unless you have an Apple system. Apple and many other products that can work off US/Eur/Asia based electrical without modification will mostly survive.
Its NOT a doomsday device…
That said IMO I don’t see Noko fielding it. Mostly because it brings not so much destruction but rather interruption, unless you are directly under the blast itself. NoKo is not deep in nukes or anything else so I think their goal would max destruction which would be a low level blast over a major city for the people kill and ground level destruction. San Fran, Chicago, NYC, and of course DC would be KEY targests due to population density and the seat of govt.