Equipment Protection

[Mark_at_TH]

Hi guys I?m newly registered and I have to say that I?m not a licensed electrician or contractor so you guys may boot me pronto. Especially after you find out that I was an Ironworker for 30 years.
I can say that one of favorite crafts to work with on the big jobs was electricians.
Although most of them couldn?t sing very well they were exceptional hands and a great bunch to work around.
I always hire my electrical work done by the pros so no beef with me there.
While reading the home page I was really impressed with information which even a layman could understand so here I am picking your brains.
The reason I?m posting is mainly safety related questions and possible solutions.

95% of my business is internet related mail order sales so I find myself spending more and more money on these high dollar computer gizmos. I?ve got all the surge protector/interrupters that are normally purchased with computers and accessories and even subscribe to Watts Dog which is some sort of pole mounted surge protector system offered by OG&E our local power company.

My main concern is the grounding of my telephone cable. We live in the country about 5 miles form the nearest town. The telephone lines are routed to us through buried cables. If I understand my SBC repairman correctly these cable are the older pulp insulated type.
There aren?t many people on this line, say maybe 6 or 7 max so it?s only a 25 pair cable.
When I first started my internet business I used a 56K dialup modem to get on line.
At first I got very low connection speeds which made working online extremely agonizing.
What I found out was I had a lot of noise on the line that wasn?t really discernable to me most of the time.
When my SBC repair man started working on it he said that the cable was really old with a lot of splices, breaks in the plastic insulation, and moisture problems. He also says this damage had been occurring for some time. He said the metal sheathing surrounding the pairs has many separations and had lost it?s electromagnetic shielding properties which allowed the noise to occur.
To complicate things there are what he called some data transfer lines running in the same cable with the phone lines. These run to the REA power sub station which is about a mile from us.
He said these used a lot more voltage than the phone lines and that this was mostly the cause of the noise since the shielding was gone.
If I understood him correctly the fix he used was to take an unused pair of phone wires and turn them into ground wires between each terminal box.
Does that sound right? Anyway it fixed the noise just fine and my connection speed went from
20000 range to consistent 40000/440000 BPS which he says is nothing short of a miracle given the cable condition and distance from the terminal station (bowing here to SBCs service techs)
It works great now but here?s my concern.
Correct me if I?m wrong but what I understand is that the metal sheathing is not just to protect the pairs from physical damage and noise but also acts as a ground which keeps electrical charges away from the pairs inside the cable and directs the current to ground at terminal boxes.
If it?s damaged in many places and no longer intact does that allow the electrical charges to seek the next best conductor and travel down the pairs inside the cable?

Also does the greater electrical charge inside from the data transfer pairs in any way attract or amplify any maverick charge such as lightening?

How much more charge do those data transfer pairs have and do they present any danger by themselves in a damaged cable.
If any of this is the case what danger does this present to my equipment and phones?
It seems to me that the damage eliminates the possibility of using the metal sheathing for interval grounding at junction boxes and gives the lightening or any power surges a straight shot 5 miles long to ZAP my equipment or family.
What dangers are involved here and what solutions are available.
What can be done by the phone company to insure the max safety for my family and equipment?
Thanks in advance for your help.
Mark@TH

 

[peteo]

Good to hear that SBC was able to improve things for you. My experiences in many residential areas, by comarison, is to listen in to others conversations. The 300 pair or so which they bury is twisted pair. The sheathing foil (or DRAIN) wrapped on that bundle is well isolated. The twisted pair carries about 100 VAC during the ring function, and your technician can perform practically magical feats of testing using his/her equipment on the truck. At the point where the telco service comes to your house there is a protector, where any large standing voltages, lightning surges, etc., are sent to your home's grounding system. It is as safe as humanly possible and nothing to worry about.

 

[petersonra]

Re: Equipment Protection

What I found out was I had a lot of noise on the line that wasn?t really discernable to me most of the time.

When my SBC repair man started working on it he said that the cable was really old with a lot of splices, breaks in the plastic insulation, and moisture problems. He also says this damage had been occurring for some time. He said the metal sheathing surrounding the pairs has many separations and had lost it?s electromagnetic shielding properties which allowed the noise to occur.

A common situation. Voice lines are not really designed for modem use, and while they work fine in many cases, voice only requires about 3 kHz of bandwidth. If you lose some of that bandwidth gradually over time, you won't notice it, but your modem will.

To complicate things there are what he called some data transfer lines running in the same cable with the phone lines. These run to the REA power sub station which is about a mile from us.
He said these used a lot more voltage than the phone lines and that this was mostly the cause of the noise since the shielding was gone.
If I understood him correctly the fix he used was to take an unused pair of phone wires and turn them into ground wires between each terminal box.
Does that sound right? Anyway it fixed the noise just fine and my connection speed went from
20000 range to consistent 40000/440000 BPS which he says is nothing short of a miracle given the cable condition and distance from the terminal station (bowing here to SBCs service techs)

While I am not sure why what he did worked, I am inclined to think if it resulted in a substantial improvement I would not worry about it too much.

It works great now but here?s my concern.
Correct me if I?m wrong but what I understand is that the metal sheathing is not just to protect the pairs from physical damage and noise but also acts as a ground which keeps electrical charges away from the pairs inside the cable and directs the current to ground at terminal boxes.
If it?s damaged in many places and no longer intact does that allow the electrical charges to seek the next best conductor and travel down the pairs inside the cable?

The shield is at ground potential but is not there to collect any loose electrons. It is a Faraday shield of sorts that does tend to reduce induced noise. It is not there for safety reasons.

Also does the greater electrical charge inside from the data transfer pairs in any way attract or amplify any maverick charge such as lightening?

Typically, telco cables are buried deep enough in the ground the lightning will not affect them usually. I have read lightning tends to dissipate with a few feet of the surface. Lightning pretty much goes where it wants to and you can't really control where it goes. You can nudge it and try and convince it to go somewhere you want it to, and usually it will go there. But there is no guarantee. I would not be worried too much about them attracting lightning. From what I have read, it is not all that easy to attract lightning even when you try. And something buried four foot underground is not a likely candidate for attracting lightning.

How much more charge do those data transfer pairs have and do they present any danger by themselves in a damaged cable.
If any of this is the case what danger does this present to my equipment and phones?
It seems to me that the damage eliminates the possibility of using the metal sheathing for interval grounding at junction boxes and gives the lightening or any power surges a straight shot 5 miles long to ZAP my equipment or family. What dangers are involved here and what solutions are available. What can be done by the phone company to insure the max safety for my family and equipment?

There is no charge to speak of. They really do not represent any more of a danger then the phone wires themselves do. When a phone rings, I seem to recall there is close to 100V on the line.

Any wire 5 miles long is going to have so much impedance in it that there is very little chance lightning will travel 5 miles along that wire and attack your equipment.

Stop believing the lies told to you by surge suppressor manufacturers. Lightning damage is pretty rare and usually a common surge suppressor will not help any.

Best bet to reduce whatever damage might happen is to install a whole house surge suppressor right inside your circuit breaker box. This is something best done by an electrician who actually understands these issues. Your average electrician does not and might install it so it is safe but not especially effective.

You can also install suppression on the telco lines at the point just before they come into the house. The same caution applies. Get someone who actually understands the real issues. Most electricians, cable and telco installers do not understand the issues and you might spend a big chunk of money and get no additional protection.

I would also be inclined to put any especially sensitive equipment on a UPS. Get an on-line ups so that there is isolation between input and output. Cheap ups's allow surges to go right through and serve no purpose other than to retain power in an outage. If truth be told, most electronics equipment have front end power supplies that are pretty robust and do a good job of protecting the innards from the commonest power problems.

Surge suppressor strips are of dubious value and I would not use them as anything other than glorified power strips.

 

[Mark_at_TH]

Not that deep

Not that deep

Thanks for the info guys.
The telephone cable on our road is buried an average of 12 inches deep I believe.
I just got the service repair records for the last seven years and they show that the road grader has cut our cable about 25 times.
Erosion, grader work, and shallow original burial have taken their toll.
Still interested in hearing from some of you guys who might have more answers.
Thanks again,
Mark@TH