On 10/2/2017 7:52 πμ, Michael Moroney wrote:
Diesel writes:
(Michael Moroney)
news
alt.home.repair, wrote:
Up the street from me, they upgraded a MV distribution circuit
from a lower voltage to a higher one (13,800V I believe).
Have they been adding on to the circuits in your area? New buildings,
etc? What was the previous voltage?
No new construction/new loads in that area. It may have been done to
allow that circuit to provide an additional 13.8K feed to a medical center
a ways upstream. I am uncertain of the old voltage but the nameplate for a
regulator transformer on a nearby old circuit reads 2400V which seems kind
of low. The utility seems to have been upgrading other older/lower voltage
circuits in the area as well.
I've also seen the results of that type of surge. The top of a
pole broke in a storm and the 4800V MV distribution wires made
contact with the 120V/240V feed to houses. Two of them burned to
the ground.
Ouch! I've seen this happen before too. Doesn't typically end well for
the building and/or the electrical system/attached devices inside.
Here in Iraklion,Crete MV used to be 15kV, now it's 20 kV I think.
Usually we don't have accidents of the primary messing with the
secondary. MV distribution is all around the city with buried cables,
some of them are very old, with paper insulation. However, there was a
bad accident where a lineman was connecting a new supermaket to a 20kV
circuit, there were two buried cables, and they have a special device
that checks if the cable is live. So he checked and it wasn't. But back
at the substation they energized it and the arc flash instantly killed
him, and temporary blinding everyone at the vicinity.And in the
Thessaloniki substation, a potential transformer exploded (400 kV) and
the debris destroyed an auto transformer (400/150 kV) and there were
serious problems with power for the whole area. I have a surge power
strip on my computer and when I turn my PC off I throw both the PSU
switch and the power strip one. On my stereo I have a voltage regulator
and when off I throw the VR's switch, the power strip's and the amp's.
That should be enough. If there's an 20kV surge the PC and the stereo
would be the least of my worries.