Surge protector

How much do you need to spend to keep your expensive equipment safe?

Introduction

They say lightning doesn’t strike twice in the same place — but it doesn’t have to. A direct strike on your home can burn out every piece of electrical equipment you have connected. Fortunately, direct strikes of this severity rarely happen, but nearby hits can still produce a surge of excess voltage that can fry the insides of your nice new plasma TV, video, DVD, sound system and computer. If it’s plugged into the wall, it’s vulnerable — and it can still be vulnerable even if the wall switch is turned off, which is why we’re advised to unplug electrical devices at the wall when there’s a storm. But even low-level surges can, over time, degrade electronic components and shorten the life of your equipment.According to electricity suppliers, power fluctuations are inevitable. That’s where surge protection comes in. Surge protectors should let only a safe amount of electricity through, taking the excess and diverting it safely away from your valuable gear. So, on the whole, surge protectors seem like a good idea. But there are questions to be considered:

• How big a surge will they really protect you from?
• When they take the sting out of a massive electricity surge, or even a smaller spike, how much electricity are they still letting through?
• Is this amount safe for your equipment?
• How much do you need to pay?
• Should you buy a model that includes a connected equipment warranty so you can replace your prized electronic gear if the worst happens?
• These are all important questions, so we set out to answer them — and our findings may shock you.

How surge protectors work

A surge protector can look a lot like a typical power board, but when too much voltage gets shunted down the mains line into the device it lets only a ‘safe’ amount through to the connected equipment. The rest it channels into the electrical outlet’s ‘earth’ or ground wire. Most commonly for domestic units the crucial component that does this is called a MOV, or Metal Oxide Varistor. This component is made from a material which is a bad conductor of electricity until it receives a higher than normal voltage, then it becomes conductive. When a spike or surge occurs at a certain level above normal voltage, the MOV becomes conductive and starts to carry the excess electric current back down through the ground wire, so the damaging high voltage doesn’t reach connected equipment. Once the surge ends, the MOV resumes its ‘dormant’ stage of being non-conductive. It’s a bit like an electrical version of a pressure valve. European domestic wiring is designed for a standard voltage of 230–240 volts. If the voltage goes too far above that, it can damage electronic equipment, which usually has many sensitive components. If excess voltage lasts for a very brief time (1–2 nanoseconds) it’s called a spike. If it lasts longer it’s called a surge. Even though a spike or surge can be so brief their duration is measured in nanoseconds, they can still cause damage to sensitive components. All spikes and surges come under the heading of electrical transients.

Levels of protection

Possibly the most noticeable cause of a large surge can be lightning striking nearby, even up to more than a kilometer away. This massive electrical discharge quickly finds its way into the electrical grid and flows along power lines both above and below ground and anything else that is conductive. A surge can also be caused by other less dramatic and far more common occurrences, such as switching operations in the power supply network, downed power lines, turning on or off large industrial equipment and faults with the electrical supplier’s equipment. A direct hit by lightning, however, could instantly deliver hundreds of millions of volts that will be far beyond the capacity of any surge protected power board. Saying a surge protector will save your equipment from a lightning strike could be overstating the issue. A nearby strike within a kilometer or two however can send a massive surge in the order of several thousand volts down the line to your home, and here a good surge protector can be up to the task. Some surge protection devices will specifically say they won’t protect against a lightning strike, while others will claim protection from lightning, as well as spikes and surges. Some will claim protection from spikes and surges but not mention lightning. In a lightning storm, it’s still good practice to unplug equipment completely from electrical outlets. Even turning off the switch might not save you, as the normal household switch only disconnects the active wire, the neutral and earth remain connected. So, if in doubt, pull it out. Surge protection can also be built into your mains power board by an electrician, in the form or a surge diverter or surge arrestor.

False sense of security

Some surge protectors can give you a false sense of security. One of the problems with this type of device is that the surge protection component can fail, but the board can continue to work as a normal power board. This means that unless you replace it, the next time a big surge comes down the line it’s going straight to your now unprotected equipment!

Test to destruction

Intrigued by the durability of some of the surge boards we tested, which passed the extreme surge 4Kv test with flying colors, we wanted to see how durable they really are. So, we inflicted a series of even greater surges, of 6Kv at 30 second intervals, to see how they’d perform. This test revealed that several models are surprisingly robust. However, as with the 4Kv test, we didn’t factor the results into our final ranking. Very unlikely though it may be, surges of this magnitude can occur in remote areas, where long cable runs and fewer cables can mean greater voltages transmitted from a lightning strike. However, one result this test demonstrated is that with some boards the anti-surge circuitry can be burnt out, yet the board will still conduct power to connected devices.

What to look for

Surge protected power boards can vary greatly in price, but higher cost doesn’t directly correlate with stronger protection — it might just mean more outlets and other features. Extra features can be useful though, depending on where you deploy the board and the type of equipment it will be protecting. Here are some features to look for when shopping for a surge protected power board: Building wiring status indicator: Detects potentially dangerous wiring problems in the wall outlet. Circuit breaker: Protects the surge board from overload by connected devices drawing too much current. Fail-safe: If the surge protection fails, this stops the unit working as a normal power board. Many boards lack this feature and continue to work as a power board even after the surge protection has failed. Protected status light: A status light to indicate whether the surge protection is active or not. Other connections: Surge protected sockets for coaxial cable, modem or Ethernet network, all of which can also conduct high voltage that can damage connected devices. Outlet spacing: Allows more room for one or more devices that use a transformer block. Sockets: Check the number of mains power sockets available, usually from four to eight. Warranty: For the board itself, less important is any connected equipment warranty.

What we found

If you’re just looking for protection against mains power surges, you don’t have to pay $300 for a ‘high-end’ surge protection board. In fact, you don’t even have to pay a sixth of that! Our products would protect you from a massive surge of 4000 volts. However, it’s not always easy to tell from the packaging whether a surge board will give you the protection you want. But even though all of the devices we tested survived major surges and would provide adequate protection for connected equipment by clamping at what we deemed an acceptable voltage (under 900V), they still let through more of a jolt than you would expect from their claims. In addition, performance claims on the packaging don’t always even use the same terms. The products can use any combination of volts, amps and joules to describe performance (see Jargon buster). Even if these terms are defined on the packaging, it can still be difficult to compare performance claims across brands when shopping.

Key findings

Our testing proves that you can get decent surge protection at a reasonable price. If you live in a city, there’s generally less chance for a severe spike or surge making it to your home, but for peace of mind any of the top seven boards in our table will do a good job of protecting your equipment from mains power surges. While some are a lot more expensive than others, you may want to select one of them for other features built into the product. In selecting a board be wary of packaging claims of clamping voltage and joule ratings. We found little correlation between the figures on the packaging and our test results. There’s no hard and fast rule, but as a guide aim for a board that has as high a joule rating you can get for the money you’re willing to spend – and, as our tests showed, you don’t need to spend a lot. Theoretically, a higher joule rating should indicate better performance. Two of the most important features, however, are a status light to show surge protection is active, and a failsafe to prevent the board continuing to work as a simple power board if the surge protection fails. Protecting your gear from spikes, surges and other power fluctuations sounds good in theory, but how necessary and effective are they? Electricity, including that generated by lightning strikes, follows the path of least resistance. Outer lying suburbs, regional and country areas are fed electricity via long high-voltage links that provide a more direct path for a lightning strike to follow. If you’re at the end of one of these links, it’s more important to have some form surge protection.

Built-in protection

Electricity is a complex subject. Your electronic equipment doesn’t have to end up a blackened, smoking ruin to suffer damage from surges and spikes. It’s a matter of degree. An especially massive surge can short out your system on the spot, but long-term exposure to the morecommon type of smaller spikes and surges can gradually weaken electronic components and eventually lead to equipment failure. Power fluctuations happen all the time, and most of them happen without us knowing about them. Modern electronic equipment usually has some form of surge tolerance built in, but the level of tolerance can vary and there’s no easy way of telling exactly how much.

Surge or drop?

If you sometimes notice momentary dimming of the lights you are likely suffering voltage drops, called brownouts. These can’t be fixed by a surge protector, but might indicate a relatively unstable power supply that could also include spikes and surges. To deal with brownouts and blackouts you need an Uninterruptible Power Supply (UPS), which provides a battery backup that will cut in immediately if the unit detects a significant power drop. A UPS will give you enough battery time to shut down your equipment safely. Depending on the type of UPS, it might also regulate the current to your equipment, evening out irregularities to ensure a smooth flow of power. UPS units usually include surge protection on their battery backup sockets and may also have one or more sockets with surge protection only.

Surge or circuit breaker?

Don’t confuse surge protection with overload protection, or even a safety switch (see Jargon buster), which is designed to protect you from electric shock. A surge board should be clearly labelled as such. Neither overload protection nor safety switch boards provide any surge protection for your equipment.

Plug in safely

The normal safety precautions should always be observed when using any electrical equipment and this applies to surge protected power boards too. It’s especially important to read the safety instructions that come with the device as procedures may vary slightly from one brand and model to another and not complying fully could void your warranty.

Jargon buster

• Amps (Amperes): Maximum spike current is measured in amps. A higher rating means greater absorption capacity against sudden power spikes.
• Blackout: A short- or long-term total loss of mains electricity power.
• Brownout: A temporary drop in voltage in an electrical power supply.
• Circuit breaker: An automatic electrical switch to protect against overload or short circuit.
• Clamping voltage: The maximum amount of voltage that a surge protector will allow through itself before it will suppress the power surge.
• Dropout: Momentary loss of electrical power.
• Joule rating: A measurement of the energy a surge protector can absorb before it fails. A higher joule rating means greater protection.
• Nanosecond: A billionth of a second.
• Overload: Also known as overcurrent. A larger than intended electric current that can cause excessive heat or fire.
• Response time: The time it takes to respond to a surge, usually measured in nanoseconds (billionths of a second). A lower figure is better.
• Safety switch: Also known as an RCD (Residual Current Device), ELCB (Earth Leakage Circuit Breaker) or GFI (Ground Fault Interrupter). Used in electrical installations to prevent shock and electrocution.
• Transient: A power disturbance such as a spike or surge.
• Volt: Used to measure electric potential at a given point, usually in an electric circuit.

©All rights reserved for SAP International Group