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Electrical surges and spikes

J. Brad Grieve

We see them in just about every house here at Lake Chapala. Sometimes they are humming and others quietly sit in a corner, showing a little light on. But all are on guard, protecting our electronic devices. They are our electrical surge protectors and they come in various sizes and forms. They are serving an important purpose and act as a little insurance in case of an attack of abnormally high voltage unknowing entering the outlet used by your computer, etc.

First, let's understand a "surge" is when the voltage rises above normal levels for more than three nanoseconds (billionth's of a second) and a "spike" is when it only rises for one or two nanoseconds. Voltage is the measure of potential electrical energy or, to use the analogy of water flowing in pipes, voltage is similar to the water's pressure. Modern electronic devices that have small electronic parts have less capacity to handle voltages above 120 volts and can be damaged by even a simple "spike" or wear out sooner by repeated "surges" in the voltage. Unfortunately, from my research here at Lake Chapala, I have found that the voltages in homes are typically higher than the standard 120-volts. By Federal Law, the ComisiĆ³n Federal de Electricidad (CFE) must deliver to your home safe electricity that is within a 10% error band of the standard 120-volts. This means that, legally, the voltage cannot be lower than 108 volts or higher than 132 volts. While I have observed normal voltages as high has 140 volts, the majority of homes are in the range of 124 to 132 volts.

Surge protectors use a variety of techniques and strategies. Some will use a transformer to help provide a steady conditioned electrical source that is normalized and uncontaminated by unusual frequencies of stray sources. Many protectors will use a type of Metal Oxide Varistors (MOV), which are semiconductors that have an electrical resistance inversely related to the voltage, hence the higher the voltage, the lower the resistance. To use the same analogy of water flowing in pipes, an MOV acts like a pressure sensitive valve that opens when the pressure is too high.

Similar to the MOVs, some surge protectors use a gas discharge arrestor or gas tube, which acts similarly to an MOV since the gas in the tube becomes ionized, and less resistance to electricity flow permits over-voltage energy to flow to the physical ground.

Both methods, will allow the extra voltage to flow out to a parallel circuit and out the physical ground. Hence, the surge protector will always need a good physical ground. Those surge protectors I find simply connected to a two-prong outlet really are not providing surge protection since the extra voltage cannot escape out to the physical ground.

Some protectors are designed differently and have the circuit protection in series. Hence all electricity will flow through one circuit, essentially holding back the electricity and gradually allowing the extra energy to flow out afterwards like a dam holding back the water flowing in a river. This will use less energy, since the excess energy is not dumped out into the physical ground. The manufacturers of protectors that use series circuits claim that this provides better protection that is quicker and more reliable.

The surge protectors will also have a backup protection fuse or small circuit breaker to limit the electricity flowing through the unit. Also, the protectors typically will have a light to indicate the primary protection (the MOV or gas tube) is functioning correctly, and sometimes to assure there is a good physical ground to the unit. Periodically, check that these lights are on to assure that you have surge protection.

Another type of surge protection unit is called a Uniform Power Supply (UPS). The UPS has a temporary battery backup system designed to permit the continued flow of electricity even when the main electricity supply is shut off. Some of these units also supply conditioning of the electrical signal (to remove noise) and are more expensive than the standard surge protector due to the extra circuitry and battery. Due to their higher value, it is worth considering putting a surge protector between the wall outlet and the UPS, to protect and provide a longer service life for the UPS.

Published or Updated on: February 14, 2008 by J. Brad Grieve © 2008
Contact J. Brad Grieve

J. Brad Grieve is a professional civil engineer who has lived and worked in the Lake Chapala area since 1994. He is the owner of Ajijic Home Inspections and you can be reach him by phone: (376) 766-2836 or e-mail.

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