how can I protect my DSL from storms

[#1]

A direct strike on the pole outside will damage any equipment connected on the line in your house.
Also in the near vacinity the strike creates an energy zone that induces energy in to various cables including mains.
The surge protector will only protect against indirect , not direct hit.
The spikes on top of a spire are used to leech a local cloud charge to ground through the copper strap to ground,the thickness of this strap is also needed to handle the current of a direct strike.
I have seen lead flashing on a house in blobs in the gutter due to a direct hit !

[#2]

Quote from: pierre_pierre

just looked at the one by my front garden, definitely no separate earth wire, just one thick cable

Perhaps my town is unique  I have noticed the earth wire before but I checked on 3 poles within 100 yards of my home and they all have one. Camera out tomorrow  It's the thickness of fence wiring.

[#3]

Quote from: itsme

That a new one on me. Does not a surge protector break down at a certain voltage and the energy is diverted to ground?

It does for normal surges, but lightning is a different kettle of fish.
Diverting 2.21 giga watts through household wiring to ground would transform your household wiring into an impressive incendiary device.
In fact, diverting live and neutral to ground (you would have to drop both) would create the aforementioned incendiary system in your house, and your closest neighbours on the same phase as you.
I doubt they'd get a kitemark on something that did that.
Static electricity is essentially DC electricity so introducing a capacitance to the circuit hides the route.

[#4]

I'm intrigued can you give me an example of one of these devices.

[#5]

Zener Diode circuit or double pole Zener.
Metal oxide varistor.
Transient voltage suppression diode.
It all depends on how cheap your surge protection is.
All allow a certain level of voltage across and clip anything higher.
All appear as capacitors to DC, hiding the route from the static discharge.
The really expensive ones use a gas filled tube, much like a neon light.
The power is transfered across as plasma, then turned back to electricity on the other side of the bridge.
It isolates the circuit in the same way as an optical isolator does for data, but for power instead.
In theory a simple rectifier-chopper circuit would do it too, but I've never seen it in practice

[#6]

So how does a Zener diode, Metal oxide varistor and a Transient voltage suppression diode work? Do they not break down at a certain voltage and therefore conduct electricity? Also none of them would be used in series in a surge protection circuit so your comment about them acting as capacitors is factual wrong and irrelevant.
Gas Discharge tubes are fitted in the master telephone socket.

[#7]

current rating of 14AWG/ 2.5mm^2 copper cored twin and earth will carry up to 24Amps  at 240V
A 6mm2 cable can take a current of 40 - 50 amps maximum  
but 'Never' try to run cables at their maximum specified current limit
Wire current handling capacity values
mm^2   A
0.5        3
0.75      6
1.0       10
1.5       16
2.5       25
but 'Never' try to run cables at their maximum specified current limit


A/mm2        R/mohm/m           I/A
6                        3.0                 55
10                      1.8                 76
16                      1.1               105
25                       0.73            140
35                       0.52            173
50                       0.38            205
70                       0.27            265

Car audio cable recommendations
This info in from rec.audio.car FAQ (originally from IASCA handbook). To determine the correct wire size for your application, you should first determine the maximum current flow through the cable (looking at the amplifier's fuse is a relatively simple and conservative way to do this). Then determine the length of the cable that your will use, and consult the following chart:
                             Length of run (in feet)
   Current     0-4  4-7 7-10  10-13  13-16  16-19  19-22  22-28
     0-20A      14   12   12     10     10      8      8      8
    20-35A     12   10    8      8      6      6      6      4
    35-50A     10    8    8      6      6      4      4      4
    50-65A      8    8    6      4      4      4      4      2
    65-85A      6    6    4      4      2      2      2      0
   85-105A      6    6    4      2      2      2      2      0
  105-125A      4    4    4      2      2      0      0      0
  125-150A      2    2    2      2      0      0      0     00

Lightening conductor cables from one company can be viewed here its very heavy  cabling

[#8]

can  household ring main circuits deal with a lightening strike ?

[#9]

Quote from: itsme

So how does a Zener diode, Metal oxide varistor and a Transient voltage suppression diode work? Do they not break down at a certain voltage and therefore conduct electricity? Also none of them would be used in series in a surge protection circuit so your comment about them acting as capacitors is factual wrong and irrelevant. Gas Discharge tubes are fitted in the master telephone socket.

Yes they do break down at a certain voltage and 'avalanche'. That's the whole point. I don't think you really understand what surge protection is.
When a voltage above what's allowed (a surge) tries to pass through the circuit. The avalanche device runs the excess voltage to ground.
Until the surge happens, the avalanche device is an open circuit. There's no way to ground through it.
All of them have capacitance, that's how they work. Just because they're not Capacitors doesn't mean they don't act like Capacitors.
You could achieve the same effect if you rectified the input power, ran a capacitor between the circuit and ground and then chopped the signal back to AC.
They just do it more efficiently and cheaply.
Static electricity is not AC, it's not DC either. It follows most of the rules of DC, but not all.
It doesn't follow every route, filling the circuit. It follows one route, the path of least resistance.
The route is planned from the ground up to the cloud, the lightning then follows that single route down.
If Earth is only part of the circuit when there it a surge, the 'signal' can't travel up through it to the cloud (unless you happen to have a surge right before a lightning strike).
It all boils down to this. If a surge protector was designed to conduct lightning, I doubt they'd be allowed to sell it and they certainly wouldn't guarantee it.
They're designed to Protect from surges, small surges they conduct away. Big static ones they hide from, not conduct them through your household wiring.

[#10]

the kind of surges in power  that I would associate with  mains electronic surge  protection devices
are surge controllers used to regulate household mains equipment
such devices are watching  the line for things such as their transformers  first switching on,
and  then waiting a short while for back EMF to be generated
I cant see them able  for controlling  the power in lightening
and was the main reason why I asked the question
'how can I protect my DSL ' in the first place .

Either I protect the whole house by a lightening conductor to protect my home and all of my household mains wiring
and disconnect my router from BT's phone poles or make sure I purchase  insurance
Very interesting and  educational .
perhaps the national part of the grid or the towns transformers fuse first before the lightening power  reaches my house? i dont know

[#11]

Back EMF is generated when inductive loads are switched off not on.

Quote from: feroluce

I don't think you really understand what surge protection is.

I fully understand how they work, but do you as you seem to contradict yourself from having a device that block the surge to one that breakdown to run the excess voltage to ground.

[#12]

You can't get guaranteed protection for your router - although enclosing your house in a Faraday cage would come pretty close.

[#13]

Quote from: itsme

Back EMF is generated when inductive loads are switched off not on. Quote from: feroluce I don't think you really understand what surge protection is. I fully understand how they work, but do you as you seem to contradict yourself from having a device that block the surge to one that breakdown to run the excess voltage to ground.

Try reading all of the posts.
You're still muddling Lightning in with ordinary electrical surges.
Lightning goes up, it can't get up past the surge protector so the lightning can't come down.
Lightning is Not an electrical surge as classified by the surge protector.

[#14]

Quote from: giro

the kind of surges in power  that I would associate with  mains electronic surge  protection devices are surge controllers used to regulate household mains equipment such devices are watching  the line for things such as their transformers  first switching on, and  then waiting a short while for back EMF to be generated I cant see them able  for controlling  the power in lightening and was the main reason why I asked the question 'how can I protect my DSL ' in the first place . Either I protect the whole house by a lightening conductor to protect my home and all of my household mains wiring and disconnect my router from BT's phone poles or make sure I purchase  insurance Very interesting and  educational . perhaps the national part of the grid or the towns transformers fuse first before the lightening power  reaches my house? i dont know

Surge protection prevents damage from ordinary electric surges, like the ones you mentioned.
Surge protection 'hides' the route for lightning.
It works comfortably for both. Comfortably enough for Insurance companies to cover it.

[#15]

Quote from: feroluce

Surge protection 'hides' the route for lightning.

How does it hide the route, all the surge devices you have mentioned are connected in parallel to the circuit it's protecting. Give me an example of a circuit that hide the route.

Quote from: feroluce

Try reading all of the posts. You're still muddling Lightning in with ordinary electrical surges. Lightning goes up, it can't get up past the surge protector so the lightning can't come down. Lightning is Not an electrical surge as classified by the surge protector.

Sorry I should have made it clear that I have put aside the lightning side so I'm not confusing the issues. But no surge protector will survive a direct hit but they may be affective from an induced surge. Also I believe you may find that lightning does not  always go up. I believe it's dependent on the charge state. Unfortunately there is still a lot of unknowns with lightning  mechanisms.