Surge Suppressors - Your first line of defense

Without doubt, surge suppressors are 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.

In effect, 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 turning 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. Metaphorically speaking, it is an ounce of prevention that can save a big headache down the road.

Unfortunately, there is a lot of misconception surrounding the subject of surge suppression.

For many, it is as if once they plug in one of these devices across the line, all their equipment is totally secure.  These may soon find out at their own expense that this is not the case.

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 suppressor ratings

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

Surge Protection - Easily Available but...

An Introduction

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.

Monster Cable MP AV600 Power Strip	In their simplest form, surge suppressors often come as a surge protected multiple-outlet power-strip. One such typical inexpensive device is the Monster Cable MP AV600 Power Strip; this is more of a basic protection power strip and comes with a 555-joule rated surge suppressor. The joule rating is a measurement of the energy absorption capability of surge protective devices. More on surge suppression ratings later, for the time being, it is sufficient to note that a 555-joule rating indicates moderate surge suppression capabilities.
Monster Cable MP HTS800 Home Theater PowerCenter HTS800	Slightly more expensive units such as the Monster Cable MP HTS800 Home Theater PowerCenter HTS800 come with a higher joule rating; the HTS800 PowerCenter is a 1665-joule rated surge suppressor and incorporates additional surge protected connections for the phone line and the coax TV input.
Tripp Lite HT10DBS Home Theater 10 Outlets 3570J RJ11/45 Surge Suppressor	Spend a little bit more and you can easily get significantly improved surge protection. For example, at around $80, the Tripp Lite HT10DBS Home Theater 10-Outlet power strip come with a 3570-joule rated surge suppressor, and incorporate multiple-line coaxial, phone/modem, and even network surge protected connections.

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. 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 process may also cause enough current to trip the house circuit breaker, or blow the equipment fuse, thus protecting your gear.  

Surge 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 <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 beaker may require anything from 15 to 150-milliseconds to operate - 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 does represent the perfect surge suppressor. Some lack speed, while others – like avalanche diodes – though extremely fast acting, do have a 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.

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Never try to operate your gear without some sort of surge protection - it is cheaper than having to replace your home theater equipment.

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Surge Suppressor Ratings

This discussion will not be complete without highlighting a few of the most important parameters that define the capabilities of a surge suppressor; these are the UL listing, voltage rating, peak surge current, and power handling.

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.

Updated in 1998, the UL 1449 second edition became more stringent on safety issues. Further more, labeling of surge suppressors shifted to an aluminized label with an embedded hologram to guard against forgeries.

Ensure that the selected surge suppression device is labeled as ‘UL-listed transient voltage surge suppressor (TVSS) 2^nd 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 3000 and above. The higher the joule rating, the better is the surge protector capability to absorb energy spikes on the line.