Over the last week or so we've had 3 lamps literally explode into fragments. Not just go, explode & shower glass everywhere.
One was a 60w incandescent, one a GU10 and the other a cooker hood lamp. The first exploded when switched on, the others just exploded whilst on. Not all at the same time mind.
Our power is regularly 250v, can't check right now, left my DMM on a job. We have a substation at the end of the cul-delsac about 12 houses away.
Any ideas? Some kind of voltage spike?
250 is getting close to the upper limit of 253v. I'd monitor it for a while (a decent UPS with voltage measuring capability connected to a PC is handy to log this sort of stuff) and make a complaint.
Could be, do you get visible changes in output from incandescent lamps?
Your post made me look at the voltage plot here and I find that just before 2230 last night the volts dropped from about 243 to 228 and stayed there until 0630 when they recovered back to 240. There where a couple of other minor drops just after 0700 and nearly 0830 down to a tad above 230. The overnight drop and the suddenness of it coming and going is most unusual, did the grid have a whoopsie or was it something local?
The Medway Handyman submitted this idea :
There seem to be quite a few 230v lamps getting into the country and they would be well over run at 250v. If you are regularly seeing 250v then I bet your lamps do not last long anyway, even if 240v and despite
250 being within spec., it might be worth your talking with your supplier.
Any neighbours reported anything similar?
The only exploding lamps I have ever seen have been in very cold and wet conditions apart from one cfl which just exploded at switch on.
Adam
Voltage disturbances will almost certainly be local ( below 33Kv) there are tap changers at 33Kv and higher. You will see grid problems in terms of frequency long before there will be voltage drops..
..and somewhere on the web is a live mains frequency display.
tap changers at 33Kv and higher. You will see grid
That and a lot more here
I'll have to ask.
Good point. I had a spate of measuring a while ago & it was frequently
250/252v.I'll have to start a daily log.
Small overvoltages dont cause explosions, they cause reduced filament life. Arcover as the filament breaks can cause explosion. Are they on fuses or mcbs?
NT
A clear case of demonic possession. Have you noticed your wife's head rotating at all?
Here is one:
Fuses
Only after a few cans of special brew.
Vortex5 presented the following explanation :
Ah, going to MCBs would mean much quicker blows, fair chance it'd prevent it happening. Might also be worth checking you've got the right fuse wire in, not 10A or 15A. And maybe that, as I've seen before, you don't have more than one fuse parallelled.
NT
country". I wonder how much it actually varies throughout the country. I know they are all locked to the same frequency, but I doubt that the synching is perfect.
On Wed, 14 Apr 2010 12:13:09 +1200, Gib Bogle wibbled:
On *average* it is perfect - think what would happen if one end of the country became 180 degrees out of phase with the other which would eventually happen if there was a sustained difference in frequency. There are phase variations over the grid though.
What does happen though, is due to very long transmission lines, there can occur oscillations in the phase difference, most pronounced between southern England and Scotland, but there is no net difference in the average cycle counts.
The danger with that is if the oscillations become pronounced it can lead to high currents in the transmission lines with the risks of trips opening.
Not sure what National Grid do now, but back when the main control room was in London. there was a device nicknamed "the Scottish Wobblemeter" (really) that indicated the phase difference between the two ends of the grid. If that started oscillating, corrective measures may be needed urgently.
On Wed, 14 Apr 2010 06:24:07 +0000, Tim Watts wibbled:
BTW - this is why the Interconnectors to France and Ireland are DC - the impossibility of phase locking to another sizeable system with a weedly link.
It boggles the mind.
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