We live today in the information age in which it is created, transmitted or stored constantly in huge quantities and all handled by electronic equipment that are electric power supplied.

From the electric power supply also depends many other devices we have in our homes, whether for business or for fun.

It follows that having a stable and flawless electric power, is a factor of major importance for the good functioning of all equipment.

All electronic equipment should be powered by perfect sine wave mains and always with an effective nominal voltage, without any distortion or electrical noise.

The reality however is quite different – surges, sometimes of thousands of volts, variable nominal voltage, electrical noise caused by switching on/off electric motors or by lightning storms.

All this can cause electronic devices to change its electrical characteristics or malfunctions.

Among all the problems that occur in electric power supply, the most important includes:

Pulse (or peak): Is an instantaneous increase (<1ms) of the voltage to values that can reach thousands of volts. The pulses can enter the equipment through the electricity power supply or through the telephone line.

Causes: The pulses can be caused by lightning storms or by the return of power supply after a temporary shutdown or failure.

Effects: It can fully damage the equipment.

Noise: Surges of oscillatory nature, of high frequency, distorting the sine wave voltage from the mains.

Causes: Electrical noise is caused by many factors and phenomena: thunderstorms, on/off switching, generators, radio transmitters, etc.

Effects: In computers can introduce errors or corrupt files.

Micro power cut / Dropout: Total loss of tension between 1ms and 1s.

Power cut / Outage: Total loss of tension for more than 1s.

Surge: Voltage surge over the nominal voltage longer than 2.5s.

Causes: Surges results from the presence of high power electric motors in the vicinity of the electrical installation. When the equipment is switched off over voltage is dissipated by the electric network.

Effects: Computers and similar electronic equipment are designed to receive voltage within certain limits, so when subjected to stress outside these limits, its electronic components are subjected to a stress that will cause premature failure of equipment.

Brownout: Voltage under the nominal voltage longer than 2.5s.

Causes: Brownouts are mainly due to motor starting or moving consumer appliances such as refrigerators, TVs or CRT monitors.

Effects: The brownout effects are alike as surge effects.

From the problems above mentioned, one part is the responsibility of the energy supplier – cuts, brownouts and surges, and the others – pulses and noise – depending on the quality of the electrical installation.

All these problems are potential causes of failures that occur in electronic equipment.

There are several types of devices that can prevent some of these problems. Among the most commonly used can highlight stabilizers, transformers for galvanic isolation, mains filters and UPS.

Stabilizers are used to correct the deviation, (brownout and overvoltage) of the supply voltage relative to its nominal value.

Transformers for galvanic isolation can transfer energy between two points without connecting wire, thus preventing noise being transmitted between the network input and output to the load.

Mains filters provide protection against transients and electromagnetic interference (noise produced by some electrical and electronic equipment when in operation).

Finally, there are the UPS that, being a more complex device, integrates the devices described above and the possibility of load protection from power cuts, as it has within it an energy source: batteries.