Ignoring local induction effects (which may well be pretty significant) and ignoring reactive effects too, the peak voltage on the incoming earth to the house could be over 5 kV. There are no surge arrestors on the cable The lightning instantaneous discharge current peak was around 30 kA (seems to be the average figure used) The effective impedance to earth at the lightning strike point was half Ze, so 0.175 ohms The lightning strike was midway along the run between the nearest earth and the house The incoming cables were overhead for some of the route between the house and the nearest earth point Lets have fun with some numbers and see what might come in on the earth: I can only assume whatever came in on the earth? I'd just stopped touching the legs and was rummaging in my tool bag. A bright blue spark came out of the socket I was working on and extended into the room by about a foot.
Now for this I've come in for some ridicule in the past but I know what I saw. All of a sudden there was an enormous clap of thunder that shook the house and windows and I mean really moved things. There was the biggest electrical storm ever going on overhead. I'd pulled the fuse carrier, switched off the DP switch at the cu and checked for dead. Kneeling in front of an upstairs socket I had the two legs of the ring sticking out and the faceplate off. I was tidying up a ring circuit, replacing faceplates, changing to 2G ones etc. A bit of an aside but related: The closest I feel I've ever come to "buying the farm" is a few years back working on my own in a terraced house with a TN-S earth system.
0 kommentar(er)
