The question whether or not to protect your home appliances
with surge protection devices is a personal one, but it is something you should
take seriously, especially if you use sensitive or expensive equipment. The
cost of basic surge protection or surge suppression is minimal compared to the
price of replacing equipment such as audio or video equipment.
Surge suppression really should be used for all electronic
devices such as Computer Monitors, Televisions, Printers and DSL equipment. In
fact any equipment that is semi-conductor based. The components in some of
these devices are very susceptible to sudden changes in voltage, in particular
increases in voltage.
So how does surge protection work?
A surge protector is normally placed in the AC power line
between the wall outlet and the device it is intended to protect. Some surge
protection devices can also be used to protect telephone equipment by being
placed in the telephone line. They are designed to protect against what are
known as voltage spikes or transients in an electrical circuit that can be
caused by many different actions, some of which include:
- Circuit Breakers tripping
- Short Circuits as a result of poor maintenance of wiring or corrosion.
- Power Outages
- Fluctuations in power caused by the power generating company
- Lightening Strikes
Surge suppression devices will generally protect against
most of these eventualities, but lightning strikes can produce huge surges in
voltage in the order of thousands of volts. Even with surge protection, if
there is the possibility of lightning then the equipment should be totally
isolated from the mains supply, including the surge protection device. It is
worth noting that the lightning does not have to directly strike the power
transmission lines in order affect the consumer supply. Other than lightning,
surges in peak voltage are usually in the magnitude of several hundred volts
and most commercially available protection devices will be designed to protect
against power transients in that order.
A device designed to protect against voltage spikes will
have a rated clamping voltage, sometimes know as the let-through voltage. This
is the voltage level at which the device will divert the unwanted voltage away
from the line. The clamping voltage should be a little more than the required
voltage for the devices being protected. Most surge suppression devices will
have a clamping voltage somewhere in the region of 330 – 500 Volts, with 330
Volts being very common.
Another parameter to consider when purchasing voltage spike
protection equipment is the protectors Joules rating, where a Joule is a unit
of energy. The rating on surge protection devices will define just how much
energy can be absorbed when a voltage transient occurs, without the device
failing. A properly designed protection
device should only absorb a certain amount of energy before failing because by
absorbing energy, that energy is dissipated elsewhere in the system. A surge
protection device should be designed to fail at a sensible rating, thus
dissipating the energy to ground and away from the sensitive equipment. The
higher the rating, the better the protection and typical ratings for surge
suppression devices designed for the home should have ratings in the order of
200-600 Joules.
The time it takes for the protection device to respond to
the increase in voltage is known as the response time. If the response time is
too long then the damage may already be done, so look for devices with response
times of around 1 nanosecond, which should ensure adequate protection.
Finally, good surge protectors will have an indicator light
to give you a visual representation that the device is providing full
protection. Most devices will ‘burn out’ after a number of voltage spikes,
particularly if those spikes are of a high magnitude because the Metal Oxide
Varistor (MOV) component has a finite life. The majority of multi-socket surge
strips will still function as a basic power strip without the surge protection
after the MOV has failed, but without the indicator light, you would have no
way of knowing.
If you currently have no surge protection or are
contemplating buying new computer or video equipment then it would be wise to
invest in a relatively inexpensive surge
suppression device to protect your investment.
This article on Surge
Suppression was written by David Christie, MD at NSTUK Ltd, Website http://www.techyshack.co.uk
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