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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Soundmind: I need guidance on assessing risk. posted by Lynn on July 6, 2006 at 17:07:29:
"I live in the Scottsdale AZ area and we have seasonal monsoons that result in thunderstorms for several hours a day almost every day for a few months.
I live in an area where all of power lines are underground for miles around my house (although I am not sure how far away the transformer is, or if it is on a pole or underground).What is the risk to my equipment given the lines are underground?"
Without knowing the exact details of the type of equipment, the age, of the equipment, method of installation, maintenance program, it is impossible for me to accurately predict. However, in general, when periodically inspected, properly maintained, and replacement is made after its useful life is over, underground power distribution feeders including splices are perfectly safe and reliable when submerged in water for extended periods. At one site built in the 1960s and 1970s where I worked, many 13,800 volt feeders supporting an entire complex including one of the largest and most important nodes in the US telephone network were routed through manholes connected by underground duct banks routinely submerged in water, without any interruptions or failures during the feeders' 20 year lifespan. It should be understood that there were redundant feeders so that they could be switched off line for periodic testing (meggared) and when found out at the start of a failure mode, replaced. Many if not most new building developments in the US whether residential, commercial, or industrial use underground power distribution and they have proven very reliable. Normally, local utilities don't spend extremely lavishly on maintenance down to this level of their network and sometime wait for failures to occur finding it cheaper to fix outages than perform preventative maintenance. That is because the financial loss due to lack of available electrical service is someone elses, not their own. This is why many large corporations install expensive UPSs and backup generateors to support their most critical loads like large data centers and even build backup "hot sites" for rapid disaster recovery. It's expensive but they've usually found it's far cheaper than not having it in the long run. Also, their budgets are constrained by rates set by public commissions which try to keep electricity costs for customers to a minimum.
In my own area, most feeders and many transformers are on telephone poles and IMO they are far more vulnerable to outages. This is often the result of wind storms and late winter storms when heavy wet snow causes tree limbs to fall off or entire trees to be uprooted taking down overhead powerlines with them. I had a 2 day outage 5 years ago and numerous complaints led to a program of continual tree trimming (I would have preferred replacement with underground feeders instead.)
"Also, when I bought this house the owner mentioned he replaced the pool pump in the backyard when it was actually hit by a strike. In that case, would surge protectors even help?"
That's hard to say also (sorry to seem so evasive.) Most major telephone equipment rooms in critical installations used by the phone company have very large MOV type devices installed where power enters the room. Nothing is absolutely bulletproof but this is an indication that they felt this offered the kind of protection they'd need when a UPS wasn't necessary. Whether a particular type of protector would have saved the swimming pool pump from a particular hit would depend on its rating and the peak voltage and duration of the hit itself.
"can you recommend a UPS that would work well in an audio system that is not megabucks?"
I will have to contact a few of my old friends in the A/V and UPS business (if I can still find them) but here's a good place to start.
http://www.powerfactorinc.com/ups/powerware/fe1_4kva.htm
These should be a cut above the usual consumer types. You can see the low <5% THD and their ability to surpress SMPS spikes from being redirected to the source. I don't have any prices. Obviously, for those in the trade, prices are substantially lower than retail to customers off the street.
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Follow Ups
- Re: Soundmind: I need guidance on assessing risk. - Soundmind 18:19:31 07/06/06 (2)
- Re: Soundmind: I need guidance on assessing risk. - Lynn 19:38:20 07/06/06 (1)
- Re: Soundmind: I need guidance on assessing risk. - Soundmind 20:48:25 07/06/06 (0)
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