Dundas NSW - Have had three jobs at the one place since xmas including a fire as the result of lightning - I recall there is another fellow on list from the area maybe has similar stories - The process is annoying for the FTTC (can be 5 days waiting, for a quick hardware replacement from the good friends at Optus)
Have a great night all - JB2 On Thu, Jan 21, 2021 at 1:54 PM Brent Paddon <brent.pad...@gmail.com> wrote: > Agree, and as per the text below (cut 'n pasted from: > https://www.cablinginstall.com/cable/article/16465312/ground-potentials-and-damage-to-lan-equipment), > maybe part of the problem is that each house has a different earth > potential? > > I'm not an electrical engineer - so I'm assuming the below is correct. > > "Consider the case where a workstation in Building A is sending data to > another network device in Building B. The ground potential of each building > will be a function of the impedance of its ground system and the current > flowing through the ground. The data line, in addition to carrying data, is > also connecting together the ground systems of the two buildings. If the > ground potentials of Building A and Building B are different, a ground > current flows in the data line. This is known as a ground potential > difference. The voltage level of the data signals is increased or decreased > by the ground potential difference, causing data transmission errors. > > It is not unusual for a nominal, steady-state ground potential difference > to exist between two buildings. There are cases where the potential > difference has burned open data cables because of the current flowing from > one building ground to another. This usually indicates an electrical > equipment fault or incorrect building wiring. Weather conditions such as > rain can affect ground potential differences. The water-saturated soil is > better able to carry current to earth ground. Note that the improved ground > conductivity can either improve or worsen the potential difference problem. > Under normal conditions there should be very little current flowing in the > ground conductor. > > Transient events are a much greater source of ground potential > differences. Lightning strikes are the most obvious source and often > involve the building ground system. During a strike, instantaneous currents > of 100,000 A are possible. If the strike occurs near Building A, as in the > example above, some of this current flows through its ground system on its > way to earth ground. Besides the damage done in Building A, the high > current impulse will cause an instantaneous rise in the Building A ground > potential. For example, a 10,000-A lightning current flowing through the > building`s (ideally) 0.1-ohm ground impedance creates a 1000-V transient > rise in the ground potential of Building A. The potential difference of the > two buildings` grounds causes current to flow through any electrical path > between the two buildings. In this case, a transient surge appears on the > network cable connecting Building A to Building B. This transient surge can > last for several microseconds. Any unprotected LAN equipment connected to > the network cable in Building B will be damaged." > > On Thu, Jan 21, 2021 at 11:30 AM Paul Jones <p...@pauljones.id.au> wrote: > >> > -----Original Message----- >> > From: AusNOG <ausnog-boun...@lists.ausnog.net> On Behalf Of Karl Auer >> > Sent: Thursday, 21 January 2021 11:24 AM >> > To: aus...@ausnog.net <ausnog@lists.ausnog.net> >> > Subject: Re: [AusNOG] Lightning and FTTC - is it really this bad? >> > >> > There are two ways in to the CPE - the FTTC connection and the power >> > supply to the CPE. >> > >> > The FTTC connections are themselves powered at the curb, and so may be a >> > conduit for spikes into CPE. >> > >> > The likelihood of the cable run from the curb to the CPE getting hit >> directly is >> > probably very low, but the likelihood of the power grid getting hit and >> > sending a spike down the line to either the curb equipment and thence to >> > the CPE or to the CPE directly is unchanged. >> > Actually it's probably higher, given the greater number of powered >> devices in >> > the network. >> >> I would think a direct hit would generally let the smoke out, and then >> some. Just the EM fields from a nearby strike is enough to damage poorly >> designed equipment connected to long wires. You should see how much extra >> protection is provided in something as simple as an alarm system used in >> tropical storm locations (like Taiwan). Things like spark gaps and spike >> adsorbers. >> I'm guessing the designers of the CPE made the same assumption we all did >> - the copper is not as long so the problem won't be as bad (i.e. save money >> on protection that is normally used when connecting to phone lines). >> >> Paul. >> >> _______________________________________________ >> AusNOG mailing list >> AusNOG@lists.ausnog.net >> http://lists.ausnog.net/mailman/listinfo/ausnog >> > _______________________________________________ > AusNOG mailing list > AusNOG@lists.ausnog.net > http://lists.ausnog.net/mailman/listinfo/ausnog >
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