Power Protection - Surge Suppressors Explained (1)
Updated: December 10, 2012

Guide to Surge Suppressors
A first line of defense

Surge Protection Explained

The use of surge suppressors to guard expensive electronic gear from damaging voltage spikes and lightning strikes, is the most common form of power protection in any home entertainment setup. This is no surprise; surge suppression represents a most important first line of defense in power protection systems.

The main problem with surge protection is that there is a lot more to surge suppression than a cheap $30 multi-socket power protector strip! Unfortunately, many do not have an understanding of neither the principles of operation behind surge arrestors, nor of the ratings used to describe the surge suppression capabilities of these devices. The result is that surge arrestors are often misused and abused, leaving your expensive home theater gear with hardly any protection at all.

Tripp Lite HT10DBS Home Theater 10 Outlets 3570 Joules RJ11/45 Surge SuppressorTripp Lite Home Theater HT10DBS
10 Outlets 3570J RJ11/45 Surge Suppressor

An affordable surge suppression solution for the home complete with isolated EMI/RFI filter banks, 3570 joule surge suppression rating, 10 color-coded surge protected AC outlets, plus line protection for TV, telephone, DSL and Ethernet.

Power Protection:
AC power surges and lightning strikes

Without doubt, surge protection represent a first step towards implementing some form of power protection. Chosen properly, surge arrestors are your insurance policy against the damaging effects of power surges and lightning strikes.

Surge protection represents the most basic form of power protection and should be applied to all electronic gear.

It is a fact that many today ends up investing thousands of dollars on home entertainment electronics. Yet all it takes is a surge in the supply voltage or a voltage spike due to some induced EMF resulting from a lightning strike in the vicinity to spell disaster and turn expensive gear into a smoking heap of plastic and metal!

Investing in a suitably-rated surge protector is surely a lot cheaper than having to replace expensive electronic equipment damaged by a surge on your AC line. Metaphorically speaking, it is an ounce of prevention that can save you a big headache down the road.

Unfortunately, there are too many misconceptions surrounding the subject of surge suppression. For many, once they plug in one of these devices across the line, all their equipment is totally secure. However, these may soon find out at their own expense that this is not the case.

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In this article, we look at surge suppression devices and their role in power protection. In the process we:

Explain the operation behind surge protection devices,

Explain surge protection ratings

Identify a number of important issues one needs to be aware of when working with surge suppression devices.

Surge Protection: Easily Available but...

The large selection of surge suppressors available on the market at an even wider range of price levels makes the whole process of selecting an appropriate protection device far from simple. Many of these surge suppressors would look the same to a non-technical person, with hardly anything that distinguish the cheapest from the best.

In their simplest form, surge protection devices come as a surge protected multiple-outlet power-strip such as the inexpensive $30 Monster Cable MP AV625 Audio Video PowerCenter shown here. This is a basic power protection strip with seven surge-protected AC outlets and a TV antenna line protection input. It has a surge suppression rating of 1080-joule.

As we will explain further on in this article, this joule rating is a measure of the energy absorption capability of the surge protection devices. The higher the joule rating of a surge suppressor, the greater is its capability to suppress the energy contained in a voltage surge across the line; 1080-joule represents a moderate rating.

The price of a surge protection device is indirectly related to its joule rating (brand apart). This should give you an indication of the surge suppression capabilities of a power protection strip. For example, the slightly more expensive Monster MP HT800G PowerCenter comes with a higher surge suppressor rating of 2160-joule and incorporates additional surge protected connections for the phone line apart from the coax TV input. The MP HT800G is selling on amazon at around $43.

Some power protection strips such as the Tripp Lite HT10DBS featured at the top of this page incorporate not only a higher surge suppressor rating (3570-joules in the case of the HT10DBS), but also additional multiple surge-protected line inputs for TV antenna, cable TV and roof-top TV antenna coaxial inputs, phone/modem, and even network surge protected connections for networked devices in the home theater. In this manner, anything that interconnects with your equipment would have to go first through the surge protection circuitry within the power-strip.

How Surge Suppressors Work

The basic operational principle behind surge protection is to clamp high transient voltages while absorbing this potentially destructive energy by presenting almost a short circuit to high transient voltages. This energy is then dissipated in the form of heat, thus protecting vulnerable circuit components and preventing system damage.

In the event that the surge lasts for several milliseconds, the whole process of surge suppression may also cause enough current to trip the house circuit breaker, or blow the equipment fuse, thus protecting your gear.  

Suppressors usually make use of a mix of components to suppress voltage spikes on the line. However, the mostly used component in surge protection circuitry is the Metal Oxide Varistor (or MOV).

A Metal Oxide Varistor is an inexpensive yet super-fast acting device designed to create a short circuit across the line if the voltage across its terminals exceeds the breakdown point of the MOV. In the process, it shunts or diverts the surge current to neutral or ground.

At the breakdown point, the resistance of the MOV decreases from a normal 'very high level' (thousands of ohms) to a very low level (a few ohms).

The transition from a high impendence state to practically short circuit, takes place within just  a few nanoseconds, typically less than 15ns; a nanosecond (ns or nsec), is equal to one-billionth (10-9) of a second.

In comparison, a conventional 'fast acting' thermal-magnetic circuit breaker may require anything from 15 to 150-milliseconds to operate; that's practically 1,000,000 times slower than the average surge suppressor!

In these circumstances, the conventional circuit breaker is too slow to provide some form of protection to sensitive electronic gear.

The Metal Oxide Varistor is not the only surge protection component; gas-tube surge arrestors, avalanche diodes (similar to power zener diodes), and reactive type passive circuitry using inductors and capacitors, all possess the desired electrical properties required to dampen a transient behavior.

However, none of these devices represent the perfect surge suppressor. Some lack speed, while others—like avalanche diodes—though extremely fast acting, have limited energy absorption capacity. For this reason, commercial surge protection devices combine several of these technologies arranged in multiple stages, to prolong surge suppressor life and improve response times.

Never try to operate your gear without some sort of surge protection; it is cheaper to buy a suitable surge suppressor than having to replace your home theater gear.

Surge Suppressor Ratings Explained

This discussion will not be complete without highlighting a few of the most important specifications that define the capabilities of a surge arrestor protection device; these are the UL listing, voltage rating, peak surge current, and power handling. We discuss each of these parameters to better explain their importance.

IEEE 1449 Underwriters Laboratories Listing:

Referred to as ‘UL 1449’ or simply ‘UL listing’; these represent a set of specifications that determine if a surge suppressor is safe during use.

The heat generated from powerful voltage surges can melt the plastic coating, potentially causing a fire. For this reason, most of today's MOV-based surge suppressors come with the MOV device encased in a ceramic enclosure for superior safety in the home. This ceramic enclosure is made of fireproof material similar to that used by NASA on space shuttles.

By September 2009, UL 1449 3rd edition became mandatory and imposed more stringent requirements on safety issues. Furthermore, with UL 1449 2nd edition, labeling of surge suppressors shifted to an aluminized label with an embedded hologram to guard against forgeries.

It is therefore important to ensure that the selected surge suppression device is labeled as ‘UL-listed transient voltage surge suppressor (TVSS) 3rd edition’. A UL-listing as ‘power tap’ is not sufficient.

A UL-listed TVSS does not imply that it will protect your equipment from surges, but rather that the surge protector is not likely to pose any personal hazard to you during use e.g. through electrocution, fire, etc.

Operating Voltage:

The lower the voltage rating of a surge protector, the more effective protection the surge suppressor will provide, however…

The voltage rating has to be in line with the respective application. If a surge suppressor is going to be used across the AC line, then the voltage rating of the suppressor has to take into account that the 120 volts ac in the US, (230/240 volts in Europe), represents the root means square (RMS) value rather than the peak.

In this case, the chosen suppressor voltage rating should allow the normal peak AC voltage to exist across the line. Peak mains AC voltage is 1.414 times higher than the specified RMS value.

Peak Surge Current:

This represents the maximum transient current that the suppressor can handle during a surge.

If you are applying surge suppression only at the point-of-use—in other words, you are not making use of additional surge protection at the point of entry of your AC mains supply—then you need to look for a peak current rating of 55,000 amperes or higher.

Joule Rating:

Also referred to as ‘Energy rating’, this is a measurement of the energy absorption capability of the surge protection device. Typical values may vary from 500 to 5000 and above. The higher the joule rating, the better is the surge protector capability to absorb energy spikes on the line.

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 Article Content

Issues discussed in this article:

Blue bullet  Introduction: AC power surges and lightning strikes

Blue bullet  Surge Protection: Easily available but are you fully aware of the level of protection you have?

Blue bullet  Surge Suppressors: A simplified how-it-works explanation

Blue bullet  Surge Arrestor Rating: Understanding the most important surge suppressor ratings

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