What are transient voltages?
The power disturbance known as a "transient" is a very brief but extreme bursts of extra energy. They can occur on a.c. power lines, signal, telephone or data lines. A transient can also be referred to as a "spike" or a "surge".
Are transients a new problem?
No. Transients are a natural result of any electrical activity and have existed ever since Edison ran the first power line. They are generated every time wires, motors or electrical elements are energized or de-energized.
Where do transients come from?
About 35% of all transients come from outside the facility from such sources as lightning, utility grid switching, switching large capacitor banks on the utility lines, electrical accidents or heavy motors or loads from nearby industry. The remaining 65% are generated inside our homes and facilities and come from such unsuspected sources as microwave ovens, laser printers and copiers, air conditioner motors and even lights being turned on or off.
Why should I be concerned about transients?
Each generation of microcircuit chips becomes faster, smaller and more densely populated. This technological progress comes with tremendous risks as these new designs are less tolerant of small electrical disruptions and are more susceptible to damage and disruption. Added concern comes from broad use of microprocessor technology. Every new automated function makes us that much more dependent on computer technology and that much more vulnerable to inconveniences when these devices fail. These disruptions can have devastating effects, with life and death consequences when interrupting communications, traffic control or medical functions. At the very least, these disruptions can cause inconvenience and frustration.
How can I avoid these frustrations?
The only sure ways to avoid these problems are to (1) not use microelectronics or (2) don't turn them on. However, the only reasonable way to enjoy the use of these modern conveniences with minimal frustration is to assure that the electrical supply is kept within micro-circuitry tolerances through the use of transient voltage surge suppressors (TVSS) or surge suppression devices SPDs.
Are all surge suppressors created equal?
No. While the same suppression component, known as Metal Oxide Varistor (MOV), is used in most surge suppressors as the primary clamping component, the supporting circuitry, circuit board design, wiring techniques, and product features can result in product qualities that range from highly effective to ineffective and dangerous. While not always true, generally "you get what you pay for." If you are purchasing from a reputable source you will generally have a selection of high, medium and lower quality devices. Nevertheless, the cheaper devices are made that way by sacrificing either protective or safety features.
Is it just my computer that needs protection?
No. Any microprocessor device is vulnerable to damage or disruption and should be protected. Home electronics, appliances, electronic instruments, communications and telemetry equipment, medical instrumentation, factory automation and PLC's, electronic ballasts, traffic controllers, banking, theme parks, cash registers, gas pumps, etc. etc. etc...
How do I protect all these devices?
Any product that plugs into a wall outlet can be easily protected with a plugstrip or wallmount suppressor. Larger devices such as appliances, "direct wired" equipment, process automation, specialty equipment and full facilities can be protected by wiring "panel mount" suppressors to the electrical panels. While this sounds complicated and costly, it is actually quite simple and surprisingly inexpensive in light of the protection provided. This is also an excellent way to improve the overall protection provided by point-of-use protectors. By eliminating the bulk of the transient at the service panel, the suppressor at the outlet is able to do a better job and eliminate more of the disturbance.
What is the difference between a "transient" and an "overvoltage"?
First let’s define the two terms. The IEEE Emerald Book defines a transient a.k.a. surge as, “A sub cycle disturbance in the ac waveform that is evidenced by a sharp brief discontinuity of the waveform. May be of either polarity and may be additive to or subtractive from the nominal waveform.” Overvoltage defined by the IEEE Emerald Book is, “A rms increase in the ac voltage, at the power frequency, for durations greater than a few seconds.” In comparing the two definitions, the one item that stands out is time. Here are two different disturbances, one being the transient, very short in duration with a voltage spike greater than two times the rms voltage. Then there is an overvoltage which has a longer lasting rise in the rms voltage most likely lasting a few seconds or longer.
The two definitions leave a gap in time that is not addressed between a transient and an overvoltage. This gap is best known as a swell. The complication with a swell is that some documentation (even within IEEE) have a swell defined as lasting in the millisecond range to a minute. It is not the purpose of this explanation to raise more questions, but to bring forward that transients and overvoltages are two different disturbances that require two different technologies for protection. The overvoltage causing a slower burn of wire and equipment is protected against by the circuit breaker and/or the fuse. The transient causing damage to more sensitive electronics or continually breaking down such items as motor windings is protected against by Transient Voltage Surge Suppression (TVSS). There is a common myth that TVSS protects against overvoltages but it does not. TVSS is a whole separate industry from circuit breakers and fuses that involves technologies such as Metal Oxide Varistors, Silicone Avalanche Diodes, Gas Discharge Tubes, and more.
I have circuit breakers why would I need Transient Voltage Surge Suppression (TVSS)?
The two technologies provide separate functions. The circuit breaker is designed to protect your home, business, equipment, and possibly even your life from an event such as a short circuit. The TVSS or Transient Voltage Surge Suppressor is designed to protect your equipment from events such as extremely short duration high electrical spikes. These electrical spikes or transients are an everyday occurrence, and can be caused by everything from turning a light bulb on to a lightning storm. However most spikes are of low energy. Some spikes inside facilities however can reach up to 10 kA which could possibly cause irreparable damage to one’s equipment if one did not have TVSS installed to redirect the harmful voltage away from the equipment.
Fortunately electrical short circuits are not an everyday occurrence at a given site. Short circuits being quickly defined as an accidental low resistance path in a circuit causing abnormally high current flow. It is this abnormally high current flow that could cause damage if it were not for the circuit breaker which senses this high current and opens the circuit. When installing TVSS it is proper practice to consider what type of Over Current Protection (OCP) the TVSS unit has. Some TVSS units may have internal fusing for OCP and some may have a circuit breaker for OCP. If the unit has internal fusing a circuit breaker may serve two functions. First, it will take the TVSS unit out of the circuit like a switch, and second it will protect the circuit from any over current as the circuit breaker is designed for.
How fast does my response time need to be?
ANSI/IEEE Standard C62.41.2-2002 goes to great lengths to define the waveforms that are used in today's Surge Protection Device (SPD) industry. These waveforms have various time scales, but one of the most standardized waveforms falls in the time scale of 8/20 microseconds. Before we go further let's review time scales. One second is 1000 times longer than 1 millisecond (.001 seconds) and a million times longer than 1 microsecond (.000001). Moving down the time scale we have 1 nanosecond (.000000001). In terms of speed, one nanosecond is a billion times faster than a second. Now the last stop (at least in our progression) will be at 1 picosecond (.000000000001) this is a trillion times faster than a second.
Here at EFI Electronics a major part of our surge suppression design relies on Metal Oxide Varistors (MOV) technology. Keeping things extremely simple these MOVs turn-on and conduct when a certain level of voltage is exceeded. The response times for most MOVs is under 50 nanoseconds or 20 million times faster than a second. Compare this to the 8/20-microsecond waveforms used in the industry today. The "eight" part of the waveform is for the rise time and the "20" part is for the decay time of the waveform. So a typical device should have components that can react faster than eight microseconds. With MOV technology we have response times much faster than eight microseconds.
Response time just doesn't apply here. One could consult MasterSpec Transient Voltage Suppression 16289-E3 if they wanted to find this more eloquently put, but the point to be made is response time has no place in MasterSpec, UL1449, or NEMA LS-1. Yes, we all want our equipment to respond fast, but with today's components the mainstream suppression technology is doing this very well. SPDs that claim response times in the picosecond range are promoting a requirement that nature itself would struggle to meet as light can't even travel one meter that fast.
Is bigger better when it comes to kA ratings?
Yes and no. When dealing with surge protection there are two main areas where this kA argument comes into play and that is at the main service entrance and at any branch panel down line of the main service entrance. When deciding what kA rating to install keep these four things in mind: cost, space, and consider transient factors i.e. is it a high lightning area, does the factory next door put a lot of transients on the line? Starting with cost keep in mind that usually a higher kA rating costs more money. You may be buying extra protection that is not needed. Then there’s space and weight. More kA generally means you’re buying something larger. This might be taking up valuable space that is needed by something else. Lastly, there are the transients themselves. IEEE suggests that most transients entering a service entrance are less than 10 kA.
Why would one need a TVSS unit rated for 400 kA when most transients are well under 10 kA? The rating of the unit doesn’t dictate the size of a surge it can take, but often gives some indication of how robust it is. It could be argued with a substantial certainty that anything within a 400 kA lightning strike probably would not survive even if there were a TVSS unit rated at 400 kA. However, a more common 40 kA lightning strike may occur. In this case the strike hits the power pole the energy begins to disperse its various ways and by the time it gets down to your service entrance there will be well under 10 kA. With a 200 kA unit the service entrance could be protected with the same results as a 400 kA unit and for less expense. This same philosophy is true at the branch panel. A 120 kA unit could do the job of a 200 kA unit for less cost. So no, bigger is not always better. What is better is determining if you are in an area prone to transients and how sensitive is your equipment to these transients. Then using this information to determine the size of kA rating you need for your business or home.
Are the UL and CSA labels a guarantee of quality?
Yes and No. While the UL and CSA labels are mandatory as the minimum indication of safety, it is only a minimum indication of safety. The UL 1449 2nd Edition and CSA do not verify that the product meets the manufacturers specifications nor do they verify the product's capacity to protect. The surge voltage rating only verifies that the product contains suppression components. UL's best surge rating is so easy to achieve that even the least capable product can achieve what appears to be a respectable rating.
How about European CE marks?
Like UL and CSA, the CE mark is only an assurance that the product meets minimum safety requirements and is environmentally safe. It is an excellent starting point but certainly not an assurance of quality.
How long will my EFI protection device last?
Under normal operation, your EFI protection device will operate indefinitely. All EFI devices have been engineered by an industry-leading design staff recognized for years of innovation and leadership. A world class test facility assures maximum design efficiencies and an automated factory, following ISO 9001 process controls, assures maximum accuracy, quality and dependability. EFI demonstrates our faith in our products with a ten-year warranty on all panel mount and hardwired products and a lifetime warranty on plug-in products.