How to Choose Surge Protection

Lightning2Every year, as Christmas approaches, we see an influx of PCs, modems, and other equipment killed by power surges.  It is that time of year again, so to head off some of the issues, I thought a timely reminder in order.

When a burst of energy is dumped into the grid, a surge results and the voltage at your power point will jump up above the normal 240V.  When the voltage moves above the level that your equipment is designed to handle, damage results. 

Small surges cause cumulative damage to electronics and you won’t notice it happening.  When your computer perhaps reboots, or later just dies, you won’t know that your mains power is the cause. The most obvious impact of surges is when you get a big surge, or spike, and that may immediately kill your equipment.

A surge is just one of a range of power issues you will see described with terms like spike (same thing, but shorter duration), sag (voltage drop), transient fluctuation, interruption, line noise, and others. These are all situations where supplied power moves outside the range of “normal” and is generally called “dirty” power.

What causes surges?

The most obvious source in Brisbane are lightning strikes.  Lightning is a big spark, triggered when the potential between two locations, normally charged clouds and the earth, grows big enough to cause a mighty spark to arc across the air.  Air is a poor conductor and the lightning will travel along the easiest path, so as it reaches the ground, it will jump to any tall structure that is more conductive than the air, and then follow a path of least resistance to the ground.


Lightning does not have to strike a building, or even a nearby power pole, to cause damage.  When lightning strikes, mutual induction results in a boost of up to thousands of volts in nearby cables, including phone and cable internet wiring.  Induction can result in a surge many kilometres from the strike.

The most common damage caused from lightning originates from distant strikes and results cumulative damage though moderate surges.  As strikes get closer, damage increases to the point that a surge might take out your PC with a single hit.  Surge protectors can still help at that level.  A strike that is very close, say on the power pole out the front, will create such a huge surge that nothing short of unplugging your power and other cables will protect you.

If a surge protector is a nice little spillway alongside a small and well behaved creek, maybe diverting a bit of water when the creeks flow gets a bit excitable, then a nearby lightning strike is a tidal wave smashing over the creek and spillway, drowning the whole region.  It will overwhelm everything to hit your equipment.  This is why you should unplug before a storm!

Other sources of power surges and related issues can include utility based causes such as switching generators or capacitors on and off, and local issues such as the use of heavy equipment, or even household equipment such as refrigerators, air conditioners, or fluro lights.  Ever hear the click though your Hi Fi when the fridge turns on and off?  Yeah, that’s not good!

How surges reach your gear

Network_Cable_SurgeWe see a lot of people who conscientiously unplug their equipment every storm, to only find their computer and modem not working the next day.

In addition to mains power, any other cable coming into the house can also carry a charge.  Phone lines, Foxtel, your roof aerial, and cable internet connections can all damage attached equipment.

In extreme cases the surge may pass through a chain of attached electronics.  A nearby lightning strike might fry your modem though the phone line, then run through the network cable to your PCs and kill them as well.

We see this sort of issue as burned traces and components on the mainboard, originating from the network port.

When it wasn’t a lightning strike

Electronic_RustCumulative damage can be caused when power fluctuations are not severe but are still outside the design range for the electronics.

If these types of issues happen frequently, they will cause ongoing damage to your system components until they fail.  This type of damage is called “electronic rust” and you can see the result through a microscope.

Many failed parts returned to us do not fail because of normal wear and tear, but rather by excessive wear though dirty power.

Surge Protection Standards

There are some near worthless products on the market labelled as surge protectors.  While we are somewhat protected from false statements on products in Australia, it is still very easy to massage figures for surge protectors.  The best way to compare products is to go with trusted brands and to take a look at specifications that reference standards for measurement.

UL_StandardsThe most commonly used standards for surge protectors are those developed by Underwriters Laboratories (UL) in the US, and specifically UL1449.  This standard specifies the waveforms to be used in testing, defines terminology and test procedures, and categorises the type of protector.  It’s a useful reference when comparing specification of surge protectors, as otherwise the same unit might quote specifications which vary widely depending on how tests are developed.  Better quality surge protectors tend to quote this standard in their specifications.

Others standards are published by the Institute Of Electrical And Electronics Engineers (IEEE) and other professional bodies around the world.

It is unwise to trust specifications that don’t refer to a respected standard.  Don’t take unrealistic numbers on the box at face value!

How Surge Protectors Work

There are three basic types of surge protection: SPDs (surge protective devices), line conditioning/filtering units, and data/signal line devices.  Each provides a certain type of protection but what they have in common is that their job is to manage dirty energy.  Understand they cannot create or destroy energy, only work with what comes out of the plug by modifying, diverting, or dissipating energy.

Failed_MOVDomestic surge protectors incorporate a substance that can burn away to dissipate excess energy as heat to handle surges and spikes.  When the voltage rises too high, current is diverted through this component to ground, usually a metal oxide varistor (MOV).  The energy consumed by the MOV allows the main line to come back to normal voltage for your gear, but at the same time the energy will burn away the MOV.  This means that once the sacrificial MOV is used up, the surge protector won’t be able to reduce the voltage to your gear any longer and will stop working as a surge protector, but will probably keep working as a power board.

Some surge protectors incorporate a fuse, so that if the MOV can’t handle the surge, the fuse will burn out on the line to your equipment, cutting power instead of letting a surge through.  This will only work once and then surge protector will stop working even as a power board, so they are not common in domestic protectors.

More advanced surge protectors incorporate components designed to massage the power signal into a perfect form in order to keep electronic gear happy.  There are many ways to do this and the most effective can be quite expensive to build.  Fortunately while this feature is a useful it is less important for most household electronics than the basic surge protection.  It can be of significant benefit to some equipment, but buy a high quality power supply in your PC, and you can do without in a typical Brisbane house.


Specifications that Matter

Energy Absorption Rating:  An indication of how much energy the unit can absorb before it stops working, as measures in Joules.  This number represents a consumable in the form of a metal oxide that is used up by many small surges, or potentially by one big surge.  The bigger the number, the longer the board will last and the bigger maximum surge it can handle.

It is important to read the fine print and check the rating based on the UL1449 standard as advertised numbers are normally much higher than the numbers based on standards and not useful when comparing products.  You want to see a number of over 1000 Joules based on UL1449.

Indicator Lights and Fuses:  When the sacrificial component used to dissipate energy is gone, or in other words when the energy absorption has exceeded the units rating, the protector no longer works to remove surges but may keep working as a power board.  There is no obvious way to tell if surge protection has failed, so some manufacturers add an indicator light to show when the surge protector needs replacing.

A surge protector may also or alternatively incorporate a fuse designed to burn out when a surge comes along that the sacrificial component can’t handle.  If the fuse goes, the board will stop working entirely.

Clamping Voltage:  The voltage where the protector will kick in.  If it doesn’t kick in till voltage is too high, the surge may damage your gear before the surge protector starts working.  A number to aim for in Australia is 275V (mains power fluctuates around 240V).  Cheap units will tend to clamp at 400V or higher.  Note the lower the clamping voltage, the more energy will be diverted to the sacrificial component over time so the protector will tend to wear out faster, but much better the protector wear out than your electronics it is protecting!

Response Time:  Indicates how long the protectors needs to start working after the voltage goes into the red zone.  If it is too slow, your gear is damaged before it kicks in.  A good quality protector might have a response time at 1 nano second or less.  Cheaper units tend to be slower and may allow significant damage to occur before blocking the surge.  Don’t confuse detection time with response time, detection doesn’t matter, response matters.

Maximum Transient Spike: How much current the device can handle when a large burst of energy comes through, such as with a nearby lightning strike.  Again look for the UL1449 rated value and you want to see big numbers, above 30,000 amps based on UL1449 testing is good.

Power Filtering / Line Conditioning:  Aims to provide clean AC power by reducing high and low voltage electrical line noise.  There are various ways to design filters and the specs here can be misleading.  Normally more components and more cascading circuits are a good thing and active tracking is a premium feature to look for.  Filtering is only on high end models.  If it is cheap and says it’s a filter, it is probably not a very good filter.

Circuit Isolation:  Some models in a power board configuration will provide isolated circuits for arrays of plugs.  Frequency isolation is less effective than circuit isolation.  This feature can be handy when you are going to plug in electrically noisy equipment into one of the banks so it doesn’t interfere with equipment in the other banks.  Particularly useful for Hi Fi gear.

RJ 45 Protection: This means there is a plug for a network cable which can stop a surge getting through from your modem/router to the PC it is connected to.

AV/TV and Cable TV Protection:   This provides a pass-through to handle surges through your aerial and/or Cable TV Coaxial cables.

Insurance:  Most better brands will back their protectors with insurance, where they will pay damages if a surge gets through one of their protectors.  In fact a close lightning strike has so much power behind that it can strike though a normal protector, and in most cases I have heard of, the quality manufacturers will still pay up.  Insurance is a nice bonus.

Warranty:  Protectors will wear out over time as they intercept surges.  The boards I have tend to last years, but that’s with pretty good normal power and high end surge protectors.   Other staff here tell me they get 1-2 years in more outlying areas where the power is not great.  Again, the quality manufacturers will tend to replace the product even when it stops because its capacity has been exceeded (I know Thor will, don’t have personal experience trying to claim with other brands).

When to use a Surge Protector?

From the Insurance Council of Australia:  It is advisable to use surge protection units, designed to minimise the effects of power surges, on all ‘big ticket’ items in the home including the fridge, television, stereo and computers.

In my view, where surge protection helps best is with sensitive electronics such as modem/routers, PCs, Hi-Fi gear and so forth.  Sensitive electronics is not just limited to what you would expect nowadays…

The last washing machine I bought stopped a working a couple of weeks later.  Turned out it was the control board and while I doubt it was a surge that time, watching the tech replace the board reminded me how electronic components are so much part of our general equipment nowadays.

The tech was near retirement and I had a good chat with him.  He was telling me that the old washing machines of the era I was replacing lasted much longer than the modern ones.  He had a bit of a conspiracy theory where he believed that the boards in them were designed only to last so long before burning out.  He knows what he has seen over the years, and that was his interpretation.  Mine was a little different, got me wondering if the issue was surges over time that would not have been a problem for older models and their simple control systems (and maybe manufacturers keeping costs down with components, so just perhaps they don’t handle normal surges as well as they could!).  I don’t have a surge protector attached to my washing machine, but instead turn it off at the wall when not in use, but it does get you thinking about equipment you do leave on.

On average, you will tend to increase the life of your electronic gear if you run it attached to a quality surge protector.

What about a UPS?

A UPS, or Uninterruptable Power Supply is often confused with surge protectors.  Some people assume they are a better type of surge protector; not true.

Eaton UPSA UPS is a battery that switches in if the mains power is interrupted.  We sell them with all server equipment so the servers have enough time to shut down without damage to files and databases if there is a power outage.  They are also used to keep critical services up for a while during power loss, such as phone systems, servers and so forth.

A UPS does not necessarily protect from surges.  Most will, but it is better to think of them as a battery backup with incorporated power protection.  Power protection in entry level UPS models is poor.

A UPS does not necessarily sit above surge protectors in a power protection range, in fact there are cases where we have sold top quality surge protectors to clients using cheap UPSs to prevent surges getting to, and through, the UPS.  It can also be worthwhile using a surge protector behind even a top quality UPS to help protect the UPS.

What are the best value brands?

Surge protectors from most major manufacturers will do at least a basic job.  You can pretty much rate them by cost, a $20 surge protector is possibly better than nothing, but it is not going to last long or do a very good job.  Think of them as a power board that might have some other benefits.

We have sold the Thor brand over the years in the high end with good results.  Reports from customers have indicated that they do their job well, and I know they look after people with warranty and the rare insurance claim.  Most of my protectors at home are Thor.

In the entry level, pretty much any major brand around the $50 mark will get you a decent if limited surge protector, appropriate to protect lower priced equipment.  We sell some Belkin surge protectors and various other brands which are all adequate for basic protection.

Bottom line is, get something for any equipment that you care about, and for expensive gear, get an appropriate high end board.  Remember to replace your protectors regularly once the indicator tells you their protection has worn out, and when you hear a storm coming, unplug!

Related Products

Power Protection products – Computer Alliance

Further Reading

Guide to Uninterruptible Power Supplies

How Surge Protectors Work

Thor Technologies Website

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