Power Surges from Lightning Strikes nearby - how to protect electronics

[[email protected]]

I live in a mountainous area that has very dramatic thunderstorms at
this time of year. Within the past 10 days, on 3 separate occasions, I
have had the following items fried when there were lightning strikes
nearby: 1 x Netgear Router and 2 x 12V power supplies connected to an
external ADSL modem.

After the router and the first power supply died, I bought a Belkin
Surgemaster - the spec is as follows:
- Model number F9H410: 1034 Joules, 19,500 Maximum Spike Amperage,
4-sockets, Telephone/Modem/DSL protection

But then today, there was another storm and the (new) power supply for
the modem died even though it was plugged into the Belkir - both phone
line and power.

I have since done some research on Google and found that the
power-strip surge protectors are not necessarily much use against
lightning strikes.

So I am looking for advice on a better solution. I have read that the
sure way to be protected is to unplug appliances and equipment during
storms but this is not always possible - we have to leave our computers
on when no-one is home in order to access them remotely etc.

Here is some futher background in case it is useful:

- Our house is Earthed by a braided wire (approx 5mm diam) that goes
from our fuse-box through the wall and into the ground about 2 metres
away. I don't know how deep it goes, as it was here since before we
moved in.
- Occasionally during these severe thunderstorms, the differential in
the fusebox trips, but usually it does not. This is a mixed blessing -
I'd rather the switch tripped than damage occurred but at the same time
it's really annoying to come back from a week away and find the freezer
has defrosted iself because the trip switch has gone a few days
earlier.
- The ADSL modem whose PSU was fried twice was plugged into both the
phone socket and a mains socket the first time, but then today, was
plugged in through the Belkin Surgemaster. The Netgear router was
plugged into the mains socket, and then by ethernet cable to the ADSL
modem, and also some other computers.
- The socket that Surgemaster power strip was plugged into is about
8-10 metres of cable (within the walls) from the fusebox and ground. (I
read on some previous posts that surge protection should be within 10ft
of ground).

So any suggestions would be gratefully accepted:
- Does the above sound like symptoms of faulty Earth? Is there cause to
get an electrician out to check it?
- Does it sound like something that the phone or electricity service
suppliers should be made aware of? Is there anything they could check
or do to stop it happening?
- Is there any other equipment I can install to protect my house, and
equipment?

Thanks in advance for any information. If you need any more info about
my setup here in order to advise, then please ask.
Simon.

 

[w_tom]

Sounds like you have minimally sufficient earthing. Now every
incoming utility must make a short connection to that earthing. This
is called a 'whole house' protector for some utilities. In North
America, that 'whole house' protector is installed, for free, by the
telco. But the telco protector must also make a less than 3 meter
connection to earth.

Cable requires no protector. Its ground block connects short to
earthing by a hardwire.

All AC electric wires must also connect to earthing. But if
earthing all directly, then no AC electric is delivered. So we use a
'whole house' protector to make that earthing.

http://www.telebyteusa.com/primer/ch6.htm

Conceptually, lightning protection devices are switches to ground.
Once a threatening surge is detected, a lightning protection
device grounds the incoming signal connection point of the
equipment being protected. Thus, redirecting the threatening
surge on a path-of-least resistance (impedance) to ground where
it is absorbed.
Any lightning protection device must be composed of two
"subsystems," a switch which is essentially some type of switching
circuitry and a good ground connection-to allow dissipation of the
surge energy.

Two subsystems. A protector or hardwire to connect each incoming
utility wire to earth. And protection - the single point earth ground.
Every incoming utility must make a short connection to the same earth
ground. This so that protection inside all appliances is not
overwhelmed.

Meantime you may have demonstrated what we have learned by example
decades ago. A plug-in protector can even contribute to damage of the
adjacent appliance. A protector is only as good as its earth ground.
1) So where did Belkin even discuss earthing? 2) Where is the
dedicated earthing wire? Two benchmarks to quickly identify
ineffective protectors.

Why might the PSU for DSL be fried? If phone line already has the
telco provided 'whole house' protector, then look for a path from cloud
to earth ground. A classic example is incoming from cloud and AC
electric, into DSL modem, outgoing to earth via phone line. First a
surge flows through everything in a path. Then something in that path
fails. It explains why DSL PSU would fail AND explains where the
outgoing path to earth is.

Effective protection earths every incoming utility wire 'less than 3
meters' to earth and distant from protected transistors. The Belkin is
too close to transistors and has all but no earth ground - earthing is
too far away.

 

[Bud--]

Meantime you may have demonstrated what we have learned by example
decades ago. A plug-in protector can even contribute to damage of the
adjacent appliance. A protector is only as good as its earth ground.

The IEEE and the NIST both say plug-in surge protectors are effective.

The best paper I have seen on surge protection is at
http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf
- this a paper w_tom originally provided a link to
- the title is "How to protect your house and its contents from
lightning: IEEE guide for surge protection of equipment connected to AC
power and communication circuits"
- it was published by the IEEE in 2005
- the IEEE is the dominant organization of electrical and electronic
engineers in the US
- the 5 authors have broad experience with surge suppression


A second reference is
http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf
- this is the "NIST recommended practice guide: Surges Happen!: how to
protect the appliances in your home"
- it is published by the National Institute of Standards and Technology,
the US government agency formerly called the National Bureau of Standards
- it was published in 2001
- it was written by your favorite - Francois Martzloff - the NIST guru
on surges and lightning

Both guides were intended for wide distribution to the general public to
explain surges and how to protect against them. The IEEE guide was
targeted at people who have some (not much) technical background. Read
one (or both) to understand surges and protection.

Both say plug-in surge suppressors are effective.

Note that if a device, like a computer, has connections other than
power, like a phone line, that has to be connected through the surge
suppressor also. This type of suppressor is called a surge reference
equalizer (SRE) by the IEEE (also described by the NIST). The idea is
that all wires connected to the device (power, phone, CATV, LAN, ...)
are clamped to the common ground at the SRE. The voltage on all wires
passing through the SRE to the protected device are held to a voltage
safe to the device. It was not obvious to me if all devices connected
to your computer went through the surge protector.

The primary action of a plug-in surge suppressor is clamping, not
earthing. w_tom does not recognize clamping as valid, and as a result
apparently can't read and understand these guides.

bud--