Transient Voltage Surge Suppression
You’re sitting at home watching TV when suddenly your lights flicker. Sound familiar? You’ve just experienced a power surge, also known as a transient voltage surge. These are brief spikes of power that can permanently damage computers, televisions, fax machines and any electronic components that contain microprocessors.
Power surges occur from several different sources, the most familiar is lightning, though it’s one of the least common causes. It may be surprising, but the majority of transient voltage surges are actually generated internally. Research indicates that up to 80% of voltage surges come from internal sources such as motors, florescent lighting, photocopiers, vacuum cleaners and other switching devices. This is especially true over the last ten years as more microelectronics have been incorporated into everyday life. The remaining 20% of transient surges are generated externally and tend to receive more attention because they are more immediately destructive while internal surges tend to cause cumulative damage leading to premature failure over time.
A transient voltage surge suppressor (TVSS) is a component that limits the amount of energy arising from these voltage spikes and as a result, protects electrical equipment from damage.
Most common, surge protectors (or surge strips) pass the electrical current along from the outlet to any devices plugged into the strip. If the voltage rises above acceptable levels, a component called a metal oxide varistor (MOV) diverts the extra voltage. In essence, the MOV acts as a pressure-sensitive valve that only opens if there is too much pressure. One problem with these surge protectors is that the MOV can burn out after one surge. Therefore it’s important to purchase a surge protector with an indicator light telling you when the surge protector is not functioning properly.
Another common surge protective device is a gas discharge arrestor, or gas diode tube (GDT). These tubes do the same job as an MOV, they divert the extra current from the hot line to the ground line by using a gas as the conductor between the two lines. When the voltage surges above a certain level, the gas is ionized making it a very effective conductor passing the current to the ground line until the voltage reaches nominal levels. There are a couple of considerations to take into account when choosing GDT devices. They are built to withstand high-energy voltage spikes of at least 600 - 800 volts to function and may not recognize lower voltages that may still be capable of causing damage, particularly to electronics. Therefore it is often recommended the GDT devices be used in conjunction with MOV devices.
A third device, which is probably the most ideal, is a hybrid that partners MOV devices with silicon avalanche diodes (SAD). These are semiconductors that can respond very quickly to a transient voltage surge. These devices are more effective at dissipating energy; as a result, they are more expensive. However, SAD will not degrade in use, provided their rated capacity is not exceeded.
Because different parts of a factory or commercial building are subject to different transient sources, most TVSS manufacturers recommend a zoned approach matching the perceived risk with the most suitable TVSS device.
How to Protect Yourself
1. The first line of defense is the incoming power to stop external surges. You should guard against surges on your telephone and cable lines as well which can also conduct high voltage from lightening or other sources causing potential damage to computer modems, fax machines and telephones.
2. Apply surge devices at key locations throughout the home or facility helping to protect from internal surges.
3. Utilize surge strips for localized protection for computers; fax machines, televisions and other similar electronic equipment.
French Gerleman offers a full line of surge protective devices to complement our power distribution package.