A surge protector is used to keep electronics safe from power surges, or in other words, when the voltage in a house’s wiring rises above the standard 120 volts. This can happen very suddenly during events such as thunderstorms. When the voltage goes above 120 (also called the transient voltage) the surge protector can prevent the electricity from destroying a computer or other electronic device.
First, one should know that voltage is a quantity measured as a signed difference between two points in an electrical circuit, or a measure of the difference in potential energy. Electrical energy will flow from an area of high pressure towards an area of low electrical pressure. Increases in the electric energy can destroy wiring in much the same way too much water will burst a hose.
Some people may think surges are mostly caused by lightning strikes, but these are actually rather uncommon. Usually, power surges are caused by large devices, which require large amounts of energy to run. The switch on and off of these devices disrupt the flow of electricity in the system, causing the surges throughout all the wiring.
Generally, a surge protector passes the electrical current from an outlet out to various electrical devices that are plugged into the protector’s power strip. When the electrical energy flowing through the surge protector rises above the accepted level, the surge protector will divert the extra electrical energy into the outlet’s grounding line. This can be accomplished in several ways.
The most common types of surge protectors utilize something called a metal oxide varistor (MOV) which diverts the extra voltage. The MOV forms a connection with the surge protector’s grounding wire. The MOVs each contain semiconductors that have varied resistances depending on the voltage. If the voltage is lower, the semiconductors create a very high resistance, sending the voltage to the power strip and the electrical devices plugged into it.
When voltage is very high, as, during a surge, the electrons in the semiconductors create a much lower resistance, during which the excess power will flow through them and into the grounding line. Of course, when the voltage is perfectly normal, the MOVs will do nothing. During a surge, these MOVs divert the extra voltage and instantly revert to normal when the surge is over, allowing a standard current to flow unaffected, thus saving the electronic devices from potentially damaging levels of electricity.
One other commonly used surge protection device is called a gas discharge arrestor. These are small tubes of gas which do the same job as the MOVs. Gas discharge arrestors use gas as a conductor between the main and grounding wires. At one level of voltage, the gas is a weak conductor. However, at higher levels of voltage, the electrical power itself will ionize the gas. The ionized gas then can conduct the current to the grounding line, restoring the gas to normal.
Some surge protectors also use a built-in fuse for backup. Fuses act as resistors that are capable of conducting low-level currents only. If the electricity rises above the limit, the fuse will ‘burn out’, cutting the circuit off. Thus, if the MOVs fail, the extra energy will destroy the fuse, preventing any electrical energy from flowing at all. The fuse will need to be replaced if such a thing were to happen.
All major electronics in a house should be plugged into a surge protector, especially during storms that could cause a power outage or when your circuit breaker is being adjusted or repaired. Your electronics are far safer with a good surge protector than without.