Township building called. Been having problems with computers and equipment blowing out during thunder storms. They have just been replacing the equipment.
Checked the service today, and they have a ground rod, two as a matter of fact. only about six inches apart though, in the building driven through the concrete floor.
Need some advice and ideas how we can possibly do anything for them.
Police station is also in the building and there equip damaged as well.

This kind of backs up my thoery that ground rods dont do ****

Lots of possibilities.
Ensure good grounding electrode system (it does help with lightning). Provide multi levels of TVSS throughout the building of appropriate ratings. Provide a UL Master Label lightning protection system on the structure.

TVSS?

No offense is meant, but be cautious about statements on grounding-electrode quality based on anecdotal opinion. Lighting damage is partially a statistical issue. Sometimes close-in hits cannot be defended with any amount of protection.

Does the building have an NFPA-780 system in place? What kind of surge protection is installed at the building electric-service entrance and telephone-cable entrance? Is the AC-power system, telephone-entrance protector, metal piping, lightning protection and foundation steel interconnected with low-reactance conductors? Bonding to limit {fast-transient} potential difference between these components/systems within and external to the building is a crucial part of efforts to resolve the problem.

If this is starting to cost the municipality significant money, a reputable lightning-protection engineering firm may need to make recommendations on acceptable protection practices based on national-consensus standards and their experience in the geographic region. There are likely no quick or cheap solutions.

A dated but respected general guide on surge fundamentals is www.itl.nist.gov/fipspubs/fip94.pdf
and reams of other non-vendor-based data
www.eeel.nist.gov/817/817g/spd-anthology/
www.jsc.mil/jsce3/emcslsa/stdlib/docs/Handbooks/Mil-HDBK-419A-V-1&2.pdf
www.e-publishing.af.mil/pubfiles/af/32/afi32-1065/afi32-1065.pdf ]http://www.armymars.net/ArmyMARS/Safety/Resources/grounding.pdf]




[This message has been edited by Bjarney (edited 07-02-2004).]

TVSS

Transient Voltage Surge Suppressor

Well outside of my domain of experience, but I am quite curious and have several questions. While the service has ground rods, is the grounding electrode system properly bonded to all other 'ground electrodes', eg. building steel, underground piping, etc.? Also, given that this is a township building with police, are there external communications antenna and the like? What is the grounding on these, and are the various ground systems bonded together?

-Jon

As far as I can tell the building has no surge protection or lightning aresstors.
I have always been skeptical of the surge protection you buy anyway. I dont want the embarrasment of installing surge protection which will not solve the problem anyway.
No one has convinced me these things work.
I have many commercial accounts, some of whom have surge protection, and I have still seen equip fried, from PoCo surges or storms. UPS systems with surge protection in them also seem to come up short on protection.
If lightning hits a power line or tfmr, I cannot see anything stopping that surge into the service if it so desires to do so.
Getting a "lightning protection engineering firm" sounds almost amusing. I did not know such co's existed.
I would imagine it is very pricey.
This is a municipality with not much of a budget. We are in the year 2004 and they dont even have a backup generator, and this place is the "emergency shelter" area in the event of a catastrophe.

Keep routinely replacing stuff piecemeal, but your client may get tired of doing that and magically find funds to invest is an overall less-expensive, longer term fix. If you do a little footwork and offer a studied opinion on the matter, it could be cash in your pocket. If not, then it might be cash in a competitor’s pocket.

There’s gotta’ be something to resolving the problem, or NIST and the US military would not have already spent many millions and maybe a century trying to understand the problem.

Surge arresters do work... It's all a matter of quality and upsizing above recommended levels! We are usually struck in this area ( remote valleys all OH utils ) when there is a storm. The results are spectacular on the OH gear but damage to equipment downstream of the SAs is very rare - even comms and modems.

Naturally, it is pointless to put lightning spikes anywhere near util gear - thre surge from strikes fans out from the spike and WILL travel up convenient cables

Spikes should be at least three metres apart and treated much as grounding spikes with the care used to instal them.

To protect IT and comms equ't you DO need smoothing - a good UPS should handle it but again...upsize rather than save $$.


aw... Lost track of yer traffic violations???

Can someone recommend a product that they have installed or seen work.
I would like to get something that protects the load side of the service on, not looking for the little surge protectors you mount for circuits.

I had this very problem at a concrete plant. every time it sprinkled the computers blew on the plant. I started at the service and worked my way thru the buildings. Installed a grounding triad @ the service ( none there), BTW are u sure your rods are 8' and they need to be min 6' apart? Step down transformers were grounded wrong, installed lightning arrestors on each panel and control cabnit.. Not a problem since. that was 5-6 years ago. also installed GEC @ each building ( none before )

I can only assume the lenght of the rods.
One rod is for the electric service and other looks like the phone co put it in. Only 3" apart. Does that matter? Rods for service grounds are 10' I understand, but the phone rod should'nt count?????
What kind of arrestors did you use? How much and where did you get them?

Aryton,

I'm guessing this building has a 120/240 volt 1 Ø service?

Something like the Intermatic EG240RC comes to mind:

Square D and other manufacturers make similar TVSS.

[This message has been edited by ElectricAL (edited 07-13-2004).]

Do those things really work?? I stated earlier in this post that this is not what I wanted. This seems like a "cheap fix" if you can even call it a fix. Is this what u used in the plant u installed arrestors in?
You can buy these at Home Depot, right. I am very skeptical to say the least. I dont want to waste a customers money.

When protecting equipment, a layered or tiered approach yields good results.

The whole service TVSS will have the ability to handle large surges but will start protecting at higher thresholds. The whole service TVSS is valuable for directing the energy under the high spikes to ground, but there is still the energy between nominal service voltage up to the TVSS turnon threshold to worry about.

Therefore, putting more sensitive TVSS units right at the electronics provides additional protection.

The subjective part of all this is determining what is valuable. Obviously the computer and the data stored within is at the top of the list. But, the control chips in the kitchen microwave may have equal value if that's the only way to warm the baby's milk or one has a spiritual need for the morning cup of hot coffee, or the chips in the garage door openner, or the security video recorder.

Once the client lists the most valuable electronic items, one can spec the individual TVSS for each.

For the computers, an additional level of protection can be gained by installing battery standby power systems, providing both TVSS, surge, brown out and blackout protection within the limits of the system.

I was off composing that post and missed your reply.

Yes, IMO, these things work. They are, however, sacrificial. They only can take so many hits and they are dead.

If the service for the building is direct metered, its possible that your PoCo will have a unit that will mount between the meter and the socket.

Units that are wired to the panel, to work at optimum sensitivity, require that the leads be kept as short as possible without bends. Be sure to check out the manufacturers installation instructions. An extra foot of lead not trimmed away will greatly increase the impedance that prevents the surge from getting to the TVSS active elements.

Al

I can remember back in the early Eighties when protecting electronics started spreading down to the individual dwelling.

• The first line of defense was a good ground, some argued that the isolated ground was the key.
• The next line was to install TVSS.
• Next on the list was load specific isolation transformers with primary to secondary Faraday shielding.
• Then standby power supplies of varying response times, the faster, the more expensive.
• Next came full uninterruptable power supplies.
• Then motor generator sets.

I would add two more steps:
1. Totally local power generation with fiberoptic communication (electrically nonconductive) to the outside world.
2. Place the entire stucture with the generation source in #1 inside a hardened mu-shielded encasement.

I'm not trying to be funny or sarcastic. Just making the list.

Noting that your client is cash limited, one must choose what will give the most bang for the buck.

The isolated ground turns out to be a difficult thing to actually get good results from, so it can be ignored.

I would suggest that the first most effective use of money would be for your client to go to the local computer discount store and to purchase a battery backup standby powersupply for the most valuable computer. I would get this before I got TVSS. Be sure to include any phone or cable connecting to this computer.

Next, get a TVSS outlet strip or plugin block with a lot of equipment insurance. . .the higher the insurance dollar amount and the longer the warranty period, the better the hardware will be.

Next, put in the whole service TVSS.

And if you want to spend more money then start working down the list above.

Al

Delta makes an inexpensive TVSS.

The three phase model is listed here: http://www.powerqualityanddrives.com/surge_suppressor_technology/

A similar single phase model is also available for about the same price. Send an e-mail if you want one. I'll arrange to make it available on my web page.

Here's the rule of thumb for direct lightning hits:

I get to keep your money. You get to kiss the equipment good-bye.

Frank

Ayrton, no offence is intended but after reading through all the post, it appears you might be in over your head. TVSS will work 99% of the time if properly located, and installed. But few know exactly what that means. For instance if the leads are longer than six inches, not kept closely coupled (twisted together), or terminated in the wrong location, they are rendered useless. Best protection is obtained with the TVSS unit built into the service and branch panel. But no amount of protection will work with a direct strike.

However TVSS is only one step in the process. There are other steps which some have already been mentioned by various member such as is there an UL-96A Master Label? Examining all the OSP cable (Telco, Radio, CATV, etc) entrances, bonding of their cable sheaths and SPD’s. Improper N-G bonds downstream of the main service panel and improper bonding of Xo terminals in transformers.

Yes there are many firms that offer expertise, one member, Ron is an employee of one firm. Myself, I work for a telephone company and have a whole department of engineers, electricians, and technician, which specializes in such work. Is it expensive? Yes, so is numerous outages and equipment damage.

I assume the building is an old one that has an electrical system that is outdated and never was intended to contain sensitive electronic communication equipment. It could be as simple as a radio tower coax or telephone cables entering the building without any SPD’s or sheaths bonded to the facility electrode system. Could be any number of possibilities. It may take a complete retrofit of all the electrical systems by a professional design/build-engineering firm.