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Electrical Perseverance

by Michael Gibson, CareBase


One of the focus areas for CareBase has been on helping people achieve electrical perseverance for their mission-critical systems. From over 27 years of experience helping people diagnose and solve power problems, plan mission-critical solution strategies for ensuring uptime, etc., we have seen several basic cost-effective methodologies that should be done proactively vs. waiting until seeming disaster strikes. To help move towards that prepared and proactive stance, I would like to offer the following basic strategy for power protection, or as I like to call it, enabling electrical perseverance. The strategy employs laying a proper electrical foundation, and utilizing appropriate technologies matched to the application and electrical environment.

Background

Along with a health care focus, CareBase once also acted as a 'manufacturer's representative' for manufacturers of power quality devices, such as SPDs (surge-protective devices/surge arresters); UPS (uninterruptible power systems), in indoor and outdoor configurations; double-conversion voltage regulators; frequency converters; and other custom/bespoke products that can help you with persevering through the various electrical bumps, brownouts, surges and outages that hit our systems time, and time again, and on some levels on a repetitive, wearing daily basis. We also are available to act as a power quality/power protection consultant when people are having a very hard time figuring out what to do, or having power quality problems they can't figure out.

NOTE—this article contains my personal opinions, and may or may not represent the views of any of the manufacturers whose products we formerly represented.

First, prepare to persevere—with a good electrical foundation

Your electrical foundation is your wiring and grounding; get it up to code, practice single point grounding, practice regular preventive maintenance by having an electrician keep all your connections tight, including the connections inside your electric panel(s), and verify the integrity of the wiring in all of your outlets/receptacles with a good outlet checker—these are now available at most home building-supply stores (preferably a checker/tester that also can measure impedance and voltage drop under load, but those will cost hundreds of dollars). Have your electrician or your electric utility measure the impedance of your ground rod with a ground-resistance checker, or rent one yourself. Your grounding system should be up to your local codes, and ideally should be under 25 ohms—telcos and data centers like to see under 5 ohms. If the impedance is too high, surge arrester components (usually large metal oxide varistors—MOVs) inside surge protective devices, voltage regulators, and UPS, will have high-impedance (poor) paths to ground, and may not functionally allow you to actually achieve the protection you might think you have after buying whatever you did to help protect your systems.

Also, if you have an electrician there, I strongly recommend having a stout surge arrester installed at the electric service entrance to the building, and wired as close to the ground rod as is feasible. Every inch of copper wire between the arrester and the ground rod counts during a large transient event. I would aim for something with large MOVs, around 40 mm each, and with surge ratings of at least 50 kA per leg. While lightning strokes have been recorded as high as 660 kA on high-voltage transmission towers, the average is closer to 20 kA. Consequently, if your surge arrester rating is more than 150 kA per leg you're probably just throwing money away—unless you are on a mountain top, or the highest thing around in your neighborhood.. Why get something rated higher than 20 kA? The extra mass of the larger kA rated MOVs means they will not degrade as fast as smaller ones, and will lengthen the life of the unit under most circumstances. I would forget about 'consequential damages warranties' or 'surge insurance' when making your decision. The fine print on most that I've seen usually contain caveats that would make it almost impossible to ever get reimbursed. 'Caveat emptor' if it is something sold primarily on that basis. I prefer to see specifications based on UL 1449 Third Edition (or later) testing. Surge arresters are available at almost any electrical supply house these days, and are relatively inexpensive. Meter-based units, due to their being installed directly behind the utility company's electric meter, are almost always only available through the utility company, and as proximity to the ground rod is so important to catch as much as possible of a lightning strokes leading edge, I recommend meter-based surge protective devices where possible, but they do have near-equally stout hardwire units that your electrician can install on your circuit breaker panels.

Second, identify what operations in your company are important to you, and then make an investment in 'second stage' power protection equipment for all your mission-critical systems/critical infrastructure

You need 'second stage,' or 'point of use' (POU) power protection inside a building because service entrance surge arresters can only catch the bulk of a transient; and in most commercial buildings, the odds of something causing a power quality problem is quite often due to something Inside the building, like elevator motors, laser copiers, etc. And surge arrester MOVs can't catch the extremely fast frontal wave edge of a transient event, which passes by even as the surge arrester is starting to react. Also, as MOVs only operate on overvoltages significantly outside the sine wave envelope, they cannot do anything about the corresponding spikes/line noise/hash that occurs within the sine wave envelope. They also do nothing about loss of power, single phasing or brownouts. So, you want to be careful and make sure you have proper second stage point-of-use surge protectors/voltage regulation/UPS on anything of critical importance to the scope of your mission.

What systems would cause you the most heartache or money-drain if it were to go down? Cost-justification weighting needs to always give that the highest value, much more so than just the simple cost of the hardware. Generally, it pays to have your main system/file server on its own UPS. For some applications, the economic pain of just one outage at the wrong time would have paid for ten or twenty uninterruptible power systems to have kept it up. For those kinds of apps, I recommend two UPS, designed as N+1 configurable with automatic switchover/bypass. That way, you'd have to lose utility power for some time, And two whole UPS before crashing, and in that time period, save all your critical files and conduct orderly shutdowns. Using double conversion UPS, which can handle frequency aberrations, you can easily put a small generator (and make it one that delivers a pure sine wave—if it can deliver a sine wave, they'll have that in their specifications, as it qualifies as 'bragging rights.') into the picture, and then you can have as much backup time as you have fuel availability.

Some systems just need surge protection/voltage regulation to keep on going, since some electronics tolerate outages easily (e.g., most newer Window apps can be set to autosave every 30 seconds to 5 minutes, so the most data you'd usually lose is just 5 minutes worth, but what is often devastating is loss of power at the wrong millisecond in time, corrupting your registry file irrecoverably; and on the other hand, for some applications, 5 minutes is a near eternity). Some systems need voltage regulation to keep the power flow inside on an extremely even keel (e.g., eye laser surgery equipment, sensitive lab experiments, etc.).

Third, understand the differences between basic surge protectors, precision voltage regulators, and single and double conversion uninterruptible power systems, and apply that knowledge when purchasing

There are essentially four classes of "second stage" ac protectors/conditioners/regulators/UPS: ac surge protectors/arresters / power line filters ac low-impedance isolation transformer power line conditioners PWM IGBT based electronic single or double conversion automatic ac voltage regulators ac uninterruptible power supplies (UPS), some with low-impedance isolation transformer conditioning or voltage regulation built-in, in single and double conversion topologies. And there are ac input—dc output UPS as well.

Basic ac surge protectors are now fairly ubiquitous wherever you have computers or electronics. Some work much better than others. Look for a cETLus or UL/cUL listing to UL 1449 3rd Edition or later, or CE marking for the EU, quality in the build of the unit, the clamping level (the lower the better until you get too close to the sine wave envelope) and surge handling capability. These kinds of protectors usually just shunt or divert the surge to ground—if there is a low-impedance path available. For the most part, they sit there and do nothing unless there is a significant surge, and then hopefully your grounding is good, and they'll work fast enough to prevent any damage to your equipment. Most are definitely better than nothing, but once past the service entrance, are no substitute for isolation transformer based line conditioners, PWM voltage regulators or high quality UPS for truly mission-critical systems.

Basic surge protectors do not clean up line noise, regulate voltage or provide any backup power. Due to poor engineering I have actually seen some with poorly engineered filtering that negatively interacted with switch-mode power supply noise to make the situation much worse. A simple test if you're having 'electrigeist' problems: when you unplug something from a cheap surge protector or cheap UPS, plug back into raw power, and the problem goes away, you know you have a device that is not helping you.

Again, though surge protectors for second stage protection are better than nothing at all, for mission-critical systems I recommend high-quality isolation-transformer-based line conditioners at a minimum; PWM or double-conversion sine wave voltage regulators; or high-quality line-interactive sine wave (even when on backup) UPS; or the ultimate is a double-conversion ac-dc-ac "on-line" sine wave UPS-precision voltage regulator with low-impedance isolation transformer for elimination of common-mode noise.

With modern electronics ac isolation transformer power conditioners ("line conditioners") are not used as often as in the past, and they are significantly more expensive than surge protectors, but the long-term 'return on investment' can be substantial in some instances. Some companies have achieved paybacks of less than one year simply from the reductions in 'no trouble found' service calls. There are some situations where these are not only advisable, but are considered mandatory. E.g., in medical laboratories or chip/board burn-in ovens. Isolation and ferroresonant transformer conditioners have what is called a neutral-ground bonded output, which effectively create a zero volt logic ground reference at that point, for the highest degree of chip logic accuracy as common-mode noise downstream is radically reduced while still not too far from the transformer conditioner; result, faster operations and less lock-ups or erroring. Larger UPS will often have low-impedance isolation transformers built-in to their design.

Again, my recommendation for mission-critical systems in areas where voltage regulation/isolation is not necessary, is that at minimum: high-quality surge protectors should interface between virtually all important pieces of equipment and your power (this is the strategy I use at my facility, along with a brute-force service-entrance surge arrester.

Where voltage regulation is necessary (do you ever see your lights dim/brighten?), then I recommend for the smoothest regulation, double conversion ac-dc-ac precision voltage regulators. These will also act as second-stage surge protectors.

Voltage regulators in general now come in four varieties

The oldest and slowest one uses basic tap-switching transformer technology and is useful for most basic appliance type applications needing voltage regulation; and these are almost always used where there are remote clinics with refrigerators containing medicines, in countries with unstable power, and often in conjunction with an UPS and generator

Another is ferroresonant constant voltage transformer regulation (quite impervious to electrical noise, but I don't recommend it due to the ferro"resonant" design creating audible hums, and can be amazingly annoying if put beside one's desk, plus they are incredibly heavy and use up a lot of copper and steel);

My favorite now is essentially a double-conversion ac-dc-ac on-line UPS, but without the batteries. These units actually convert the ac power into dc, and then rebuild it as a pure ac sine wave, while also recreating frequency, making them a suitable choice where you may have sine wave generators for long-term backup; again, remote clinics needing medicines refrigerated, that have generators involved, often cheap ones, that need voltage regulation, and frequency regeneration so that things stay working.

Ac voltage regulation, is virtually mandatory for systems going to developing countries with unstable ac mains. Ac double-conversion on-line uninterruptible power supplies/systems (UPS), some with isolation transformer conditioning, due to their more precise voltage regulation and frequency regulation, get you into the 'ultimate' realm for uptime, especially as generators are so common in countries where the power is known to be of dubious quality. Again, make sure your generators are sine wave, not square wave.

High quality uninterruptible power supplies are the most expensive for second stage protection. Unfortunately, many people buy "cheap" UPS thinking they are getting the protection inherent in larger "state-of-the-art" UPS. This is simply not the case. In the past, we have too often had to unplug someone from their "discount" UPS to fix their problems. It is fairly axiomatic that the cheaper the UPS, the worse the electrical output when you look at it on an oscilloscope - and you need to look at it when it is on backup, because that is when you are doing the frantic file saves and making sure your registry files don't get corrupted while doing so, and while also hoping your batteries are still in good shape, and will hold up until you're finished. Unfortunately, few people have the capability to look at their UPS power on an oscilloscope.

The least expensive mission-critical grade uninterruptible power supply we can recommend is of the line-interactive single conversion variety, such as some available in big box stores now, that (and you'll need to dig into the specifications to verify this, and if they don't tout it, you can count on it not having it) can provide regulated sine wave output even when on backup, and have a built-in automatic bypass in case of UPS circuit failure. We cannot recommend basic standby UPS for any mission-critical applications, as it is just too axiomatic, you get what you pay for. If you value your systems, you need to protect them accordingly.

The UPS we recommend for mission-critical systems/critical infrastructure, especially those backed up by a sine wave generator, are any of the true on-line double conversion ac-dc-ac sine wave UPS with built-in automatic bypass. Or get two N+1 UPS (redundant) modular, and scalable systems. In my opinion, this is simply the most reliable configuration on the market for mission-critical servers and telecom systems.

To make your power availability last even longer for worst-case scenarios, I would also recommend an ethanol, or other fuel, generator to back up a double conversion ac-dc-ac on-line UPS. Worst-case scenarios do happen. Remember when one tree limb fell on one low-voltage power line in rural Oregon, and the local grid safeties cascaded all the way up to where seven Western Area Power Administration (WAPA) states ended up being without power for six hours? I'll never forget the WAPA spokesman on the news saying not to worry, the safeties all worked, we didn't lose power to the whole country — from one tree limb falling on a power line out somewhere in the mountains of Oregon; I felt so reassured. Murphy's Law will inevitably present itself; be prepared.

For outdoor applications, some manufacturers make some of their product lines in outdoor rated enclosures, sealed or with conformal-coated circuit boards for moisture ingress protection, and with proper venting where batteries are used. Most all outdoor power products have heavy-duty surge arresters for lightning protection. Special wiring, adequate ventilation/heat-sinking for high temperatures, applicable local code requirements, venting for batteries (except for lithium-ion), ease of access for repair, mounting high enough off the ground so you don't have flooding from torrential rains getting into them, and other elements particular to your installation are all things that also need to be seriously considered.

There are also five other power quality elements you should know about:

Dc-ac inverters are a product category to themselves. These inverters come into play for telecom applications or dc solar panel/wind/hydropower applications where it is necessary to provide ac power from an existing battery bank or dc power source. Inverters with sine wave output are used inside some higher quality generators, and as the second stage of double conversion ac-dc-ac true on-line UPS.

Automatic transfer switches (as mentioned above) for enabling redundant use of true on-line sine wave UPS with zero transfer time, dc-ac inverters, or other sine wave ac power sources such as two separate utility feeds that large hospitals often have, to achieve the highest levels of uptime. If one UPS or power source fails for whatever reason, the ATS simply switches over to the redundant power source fast enough that the load stays up. These vary in quality and performance manufacturer to manufacturer.

Make sure your electrical wiring is up to code, and that is has a well-connected and low-impedance ground rod, and tight "single point grounding" (NEC - NFPA 70). Beware of multiple ground rods or grounding elements not bonded together. Your electrical contractor or electrical inspector should be able to help you verify the quality of your grounding system. Surge arresters divert surges to the grounding system. If a good 'earth ground' is present, and your wiring is tight and up to code, your surge protection strategy will do its job well. And of course, don't forget static mats or some other static electricity strategy for sensitive electronics where static electricity may be an issue.

For long-term back up strategy, please consider a backup sine wave generator for your premises, installed to local code requirements. There are a variety of good 'computer grade' ones on the market. Make sure yours has a pure sine wave output, with an automatic generator transfer switch (and a double-conversion ac-dc-ac UPS/voltage regulator between it and any sensitive systems/equipment). While seemingly expensive, if it ever has to come into play long-term, and your company is up and operating while your competitors are down, you might feel you got a bargain. Hospitals, 911 centers, and similar operations usually have no choice in the matter; they often are required by federal, state or county regulations to have a backup generator, and one that is tested on a regular basis.

Finally, please carefully clean your system/computer's fan(s) and air filters on a regular basis. This is a too common faux pas. Not even a double-conversion UPS with an isolation transformer output can help you if your computer or control system shuts itself down from overheating itself.

Do actually implement, not just plan, your strategy to persevere

One company with a state-of-the-art top-of-the-mountain to bottom-of-the-mountain gondola system ordered two heavy-duty surge arresters, one for the top of the lift circuit breaker panel, and one for the bottom circuit breaker panel by the service-entrance electric meter. They took a lightning hit to the metal rain canopy at the top, and lost over $30,000.00 of equipment, computers, sensors, etc. Upon investigation, the surge arresters they ordered were found never to have been installed and were sitting on a shelf in a storage closet at the bottom of the mountain, the ground rod at the top had never been verified as a good ground--and turned out that the installer had just driven it in about two feet, hit a rock, and then just cut it off, installed a split-bolt connector for the ground wire and connected the ground wire.

 

Though it visually appeared okay at the surface, after it all happened, during the investigation, the inspecting engineer pulled it out of the ground with his little finger. The grounding for the haul-rope towers had simply been a coil of copper thrown in the bottom of each tower foundation pit, where the concrete was then poured on top of them, and apparently encapsulated them. The lightning had to travel down the steel haul-rope halfway down the mountain through several towers before it finally found one with a good ground, taking out computers/controllers at the top, and each tower's haul-rope sensors along the way. The adage, "Trust, and Verify"' simply was not applied there; if you value your systems, it needs to be.

With the above you possibly have the shortest, yet still fairly comprehensive, "Power Quality Solution Strategy" ever written. Please note that it is only for general situations. You may have something unusual that needs to be addressed by a power quality consultant (typically an electrical engineer) or your electric utility company's power quality specialist (hopefully they have at least one). Also, please feel free to contact me if you have any questions you think I might be able to help you with; I am still available for power analysis work.

Take care, and persevere,
Michael Gibson