On Tue, 04 Apr 2006 09:39:59 +0100, The Natural Philosopher wrote:

It happens here every time the wind blows or we get a thunderstorm..the
power overheads get shorted by tree branches and strikes, and the
automatic trips go out, then attempt automatic reset, and if the branch
is still there, trip again,and reset again.

We get the same occasionally, the auto recloser tries three times within
a minute to re-enstate the power before locking out. Once locked out it
requires a man to come out, isolate/reroute power around the fault (there
are two ways of feeding every where around here), find and fix the fault
and reset the recloser. This normally takes 6 to 8 hours... Fortunately
it doesn't do it every time the wind blows, very few trees along the line
routes. B-)

We did have one spate, which was a tree, that would trip the recloser but
not often frequently enough for it to lock out. off 2s, on 60s, off 2s,
on 300s, off 2s, on 90s, off 2s, on 600s, off 2s, etc it did eventually
clear (ie burn the branch back on the tree) but only after about 30 mins
of this cycling...

The voltage surges are quite injurious and I have learnt NOT to set the
computer to 'autoboot' on restoration of power...

I have a small UPS that will supply power long enough to shut down the
PCs gracefully it then powers the iPBX until flat (up to 12hrs or so,
depending on how quick I can switch the PCS off). The UPS doesn't restart
on power return until it has got back at least 15% battery capacity.

And a massive switch on transient is almost guaranteed to flip a 30mA
'whole house'RCD...which is why I stuck a 100mA in mine...

A "whole house" RCD should be a 100mA time delayed one, so that you
maintain descrimination between the whole house 100mA one (there for
circuit/fault protection due to poor earth provision) and 30mA
non-delayed ones for shock protection.

--
Cheers
Dave. pam is missing e-mail