TVSS's Surge Protection - Good Investment ?

[CyDog]

TVSS's Surge Protection - Good Investment?

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In our area we had a 34,000 Volt line fall on a 12,000 Volt
line and gave us a High Voltage surge for about 1 sec. but enough
to cause a good bit of damage. We lost about 10 Freq. Drives.
I have a few questions that you may be able to answer.

- How are TVSS's, I would imagine that they are good investments.
I am looking at the Mission Critical 300 Series TVSS Units.

- Do you know of anyone recovering any cost from the Power
Companies for damage.

- What about Power Conditioners ,I know they are expensive.We
have alot of short outages,about a sec. or 2. Would a
conditioner stay high enough for 2 sec.that we would be able
to ignore the outage, we would most likely be looking at a UPS

Thanks in Advance,

 

[gepman]

Recovering damages would depend on where you are. If you are in the United States and you could show either negligence or failure to follow the NESC (or in California GO95 [General Order 95]) for required clearances at line crossing you probably could get the utility to pay without much problem. It would be helpful if you have a recording of the power event. It would also depend on your own internal system. If you have a primary (>600V) or subtransmission (>25kV) service you should have had lightning and surge arrestor already built in to your system.

The average power conditioner will not ride through two seconds. You would need some type of stored energy device with your UPS, usually either batteries or a flywheel. As you said these are expensive and there is maintenance cost and expertise.

Some of my clients require TVSS in every MCC. I cannot tell you if they actually save a lot of drives here in California since we do not have much lightning and large surges as you describe are rare. I do know that even now with much better drive design I still see more drives blown due to either improper setup (failure to configure drive for ungrounded system when applied on one) or repeated opening and closing of either the line or load side of the drive than with utility power problems.

 

[burnt2x]

Answer on Q1:
I'm a little bit confused here, or am I missing the Q! TVSS - transient voltage surge suppression. My understanding is that these equipment are used to take care of "baby" voltage spikes mostly occuring on the low voltage side; like switching large non-linear loads, etc. MCC's supplying delicate electronics get the most benefits of TVSS's.
If the fault analysis tells you that the cause of the surges comes from the 34kV line falling on the 12kV line, I would suggest investing on your 12kV surge arresters/suppressors! Make sure your arrester duty cycle voltage is at least 125% of you continuous phase to ground voltage (about 9kV in your case). You can also invest on TVSS on your MCC's at the same time.
Answer on Q2:
Check your distribution code if you can recover damages from the utility. Depends on where you are though as well as your proof of negligence on the part of the utility.

 

[CyDog]

Is there a code that explains the distance that overhead powerlines should be from one another,for instance
34,000 Volt vs 12,000 Volt. Would it be a national standard ?

 

[gepman]

As I mentioned in my post above, consult the NESC (National Electrical Safety Code) at

http://standards.ieee.org/nesc/nescproducts.html

or whatever the governing standard is (which in California for some reason is the horribly outdated General Order 95) by the California Public Utilities Commission.

 

[dpc]

Yes, there is a spacing requirement in the NESC. I'd be surprised if the installation was not in compliance.

Circuits of differing voltage coming into contact due to upper one falling on the lower one is generally in the "stuff happens" category, unless this is a very high exposure area where perhaps they should not have had any underbuild in the first place.

The TVSS might not have survived a prolonged exposure to 3 times nominal voltage. They are intended to protect against short duration transients caused by lightning, switching, etc. But if the facility is in a lightning prone area, I'd put TVSS at the incoming service and secondary protection down in the system as well. The multi-tier approach generally works best. To best protect the drives, you really need to put the TVSS right at the drive.

 

[cranky108]

For what it's worth, what I've seen is 15kv class lines on 8 ft cross arms, and 34.5kv on 10 ft cross arms.
But it's one of those things two phases on on side of the pole and one on the other.

 

[itsmoked]

I have actually never heard of our PoCo not covering repairs caused for this type of fault. They may not! But every story I have heard was covered. Even in wind related tree falling cases. Even car wrecks. I suspect they go after the car drivers in some cases.

In a recent case a friend who's tiny back yard has some high voltage lines that appear to be directly over his veranda. They're hung on huge octagonal metal poles and are more than an inch in dia. A tree limb (Eucalyptus) brought them down on the LV wires below and onto his veranda. It was very exciting.. And blew everything in his house including things turned off. The PoCo replaced everything without argument even though it was a tree limb issue.

CyDog; I would certainly inquire - the sooner the better.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[CyDog]

I am thinking of purchasing some Surge Protection.
What do you think of the following companies and TVVS's:

Mission Critical 300 Series TVSS Units

EFI Electronics ( A Square D Company )EMA Modular Transient Voltage Surge Suppressor (TVSS)

Thanks for all your responses ,it's a tough decision.

 

[dpc]

You might also check GE. Theirs are really just as good as anything else once you sift out all of the marketing hype.

The absolute keys to making any of these devices useful:

Put them as close to what you are trying to protect as possible.

Provide short, straight, and substantial grounding connection from the TVSS to ground.

 

[rovineye]

I have used Magney Grande (shipboard) for quite some time. They are responsive, affordable, and equipment is reliable in our testing. BUT, I have never dealt with their shore based products. They can certainly tell you about their event thresholds for time and volatge.

 

[CyDog]

We have it narrowed down to 3 Brands. What is your opinion

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We have had 4 companies in to discuss and to look at our application about Surge Suppression. We narrowed it down
to 3. What do you think of the following?

All are 300kA Units accept the Square D that is 320 kA

Mission Criticalgard 300 series TVSS Units

Square D TVS4EMA32AC TVSS Units w/ Surge Counter

Surge Suppression Inc. ( Destin ,Fl.) SMLA3Y2E1

Thanks in advance for your response,