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Blackouts, hurricanes, storms… Power outages occur for several reasons, the most obvious being weather.
The National Oceanic and Atmospheric Administration (NOAA) confirms that the United States has some of the most active
weather in the world. NOAA continues to emphasize that hurricane activity will be greater than normal for the next decade.
Not long ago, the storm season of 2008 brought Hurricane Ike, which left a path of power outages from Texas to Pennsylvania.
Nearly a million people were without power for five days, while tens of thousands continued to be powerless for more than
two weeks.
Even with all of this storm activity and the incredible number of outages they come with it, severe weather still
accounts for less than half of all power outages. Power outages are not confined to the coast s and “Tornado Alley”.
From California to New York, 15.2 million people experienced a major outage in 2006 alone. Grid failure is becoming
more common as the existing infrastructure ages and is not updated and expanded to accommodate growing demand.
In its annual 2007 Long-Term Reliability Assessment, the Nord American Electric Reliability CORP. (NERC) reported
that peak demand for electricity is expected to increase by nearly 20% in the next ten years.
During the same period, committed resources required to meet demand are expected to increase by only 8.5%.
This will add additional strain to an already overburned system and will further limit the ability of utility
companies to respond to outages.
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KDE Electric is highly experienced with
burned-out residences due to fires,
for in the last twelve months we
rewired six houses that were completely burned because of electrical failures.
Most of our experience comes from dealing with service panels that
lose the grounding system during time, due to rusting (oxidation) and house vibrations.
The old panel (especially the round fuses type Edison, see bellow picture) is a potential fire hazard.
If a panel looses its ground, the neutral circuit will stay at a higher
voltage other than zero. The neutral point from the panel will then be at
higher voltage than the neutral point from the utility
transformer due to the impedance of this circuit. We soon found that
the neutral point in the house panel could be up to 40 Volts when
measured beside a good ground. It becomes a shock hazard and a fire
hazard because the circuit breaker will now stay loaded at a different
voltage, (40V smaller in our example) than the nominal (120V or 240V).
In case of overload or short circuit, it will not trip or will trip later and
not in the nominal time range.
In this case, the circuit is overloaded, heating all the elements from it, and finally, when the
insulation between wires is destroyed, the fire occurs.
Another potential fire hazard is the old metal clad cables that don�t have
the ground wire incorporated in them. This type of cables exist most
often in old houses built before 1950.
They are a potential fire hazard due to the fact that the metallic spiral becomes so
rusted through the years,that the metallic shield does not consist of a shield
like a pipe anymore. Instead, it is like a continuous spiral
inducing a lot of inductance in the grounding circuit in case of a short circuit.
This shield inductance is an electric barrier when it comes to tripping the breaker. The breaker will not
have enough current to be tripped, and if this spiral cable touches another
spiral cable or a metal pipe, then the difference in voltage between such a bad cable and
a good metal cable will end up acting like a resistor heating up the point of contact until everything will burn out.
To us, these metallic spiral cables that are not longer the metal-clad (MC) type are the cause of all fires. In
the picture at right we had such a fire. Here we see the starting point of
the fire in the house. When two of this tree cable touched the fire was evident.
The problem with this type of cables in homes is that they are very difficult to be removed.
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As a High Voltage electrical engineer with over 20 years experience,
I was always hit with the problem of protecting my circuits and equipments
against surge voltages. Think about working here for the nuclear industry at
a plasma radiation source in Tulahoma, Tennessee, where this machine was generating a
pulse of over 1 Terrawatt in 300 nanoseconds with over 1 million Volts and you
need to protect your 5V electronic equipment that is located at 12 inches apart
against those 1 milllion volts!
The same thing happen into a house bombarded by lightning, the only thing is that
the equipments from the house are far away by lightning and not at 12inch. The
lightning is a voltage discharge (plasma) between two bodies charged at two
different voltage potentials (the earth that is zero volts and lets say a cloud
static charged at 2 million volts) Because the ionization of the atmosphere
becomes so intense at one point the electric field between the earth and the
cloud breaks off producing plasma arcing or lightning. This lightning
discharges tremendous quantities of energy, mega joules of electric energy and
if you or your house are luky enough to be around this path you can get lots of damages.
There are many ways to protect your house against lightning. If you have a metallic
roof on your house make sure and connect it to a lightning rod to ground. The
best is to take a cooper rod ��in thickness and clamped in a grounding
electrode system. Good grounding electrode systems recognized by National Electrical Code are:
- the city or town cooper water pipe at the pint of entrance in your house within 5 ft.
- 2 pieces of pipe or rods 6 ft apart linked together at least 8 ft high buried in the ground at 8ft deep
- steel rebars from a house foundation.
So the first thing to protect your house and your electronics from your house is
to make sure your service panel is very well grounded and the neutral wire is
very well grounded to such grounding electrodes. This depending on the quality
of the work done by the electrician when he wired the house. This means how well are the electrical contacts
tighten in to the panel. Eventually if the aluminum splices in the panel are well
protected against oxidation. If the grounding electrode is short to the point
of contact in the earth. But the lightning strike can come into your house not
only through the 120V electrical cables but also the telephone and cable TV or
computer line path. This is why so important to keep all these cable shields
grounded to the electric ground system and eventually use some metal oxid varistors (MOV-s)
at over 50V working voltage, for telephone and cable TV. The metal oxid varistors are
components that have the resistance almost infinite when apply a voltage within working range. When apply
a surge voltage over the working voltage the resistance of the MOV decreases when voltage increases. The
means at a lighting surge an MOV shorts out the input leads. The disadvantage
of MOV is that during the lightning process might permanently short out and
get damaged so needs to be replaced. But with several dollars you can save
hundreds spent on TV , telephone or other electronic equipment that has link
though a wire with outside world.
The most effective way in protecting your house against
lightning is to install at the service panel surge protectors in a hardwired
mode. This one might cost you one hundred dollars but is very cost effective in
protecting your branch circuits from the house. This type of surge protectors
might be installed in the service panel or outside service panel against it.
The advantage of installing inside service panel is that the connecting leads
can be mounted very short making very effective, but has a disadvantage that
when fit by a big strike of lighting can explode and can make a mess in the
panel. Another type of surge protector can be installed outside in a rugged
metallic box flush mounted with the panel and keeping the connecting leads as
short as possible in order to increase the speed of answer for the surge protector.
Another type of effective surge protectors are the
plug in surge protectors. They can be plugged individually at the point of
entry for each equipment: telephone computers, TV but please buy only UL
accepted type ones because many are on the market that don�t fit the
needs. This type of protectors cannot
do the job of hard wired surge protectors mounted in the service panel. The
cannot capture hundreds of joules of energy as does one surge protector mounted
on the panel. The plug in protectors are more for protecting the electric noise
from the house generated by some appliances from the house such as well pumps
and dishwashers.
To me the most effective way in
isolating electronic equipments against noise and lightning is installing on the
branch circuits to be protected separation transformers. These are type of
transformers with the same input/output ratio and are very effective in
protecting 120V branch circuits. This might sound industrial method but is very
effective. The disadvantage is that separation transformer are all the time in
circuit consuming some energy even when nothing is fed and are bulky and the
circuit need to be dedicated for residential type.
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