It is useful to know the more common electrical faults (such as voltage variations, voltage spikes, high frequency interferences, blackouts, harmonic distortions) so as to apply the most adequate protections and avoid productivity drops. Electrical and electronic equipment are designed to properly operate from a clean and constant supply of AC voltage. High deviation from the nominal value or continual voltage fluctuations cause overheating, halts in production, machining defects, loss of data memory and programs, failures and so forth. The electricity board generates high quality electrical energy at its power stations, but cannot prevent it degrading along the distribution lines, which are subject to continual load variation and all kinds of interference. For such reasons, voltage stabilisation and protection against electrical faults are needed. To protect sensitive equipment from electrical faults, several devices are available (line conditioners, automatic voltage regulators, spike suppressors, UPS, etc.) which, depending on their characteristics, complexity and cost ensure different levels of efficacy. The choice should be made by assessing the degree of protection required, the entity of the failures and the direct and indirect costs these may cause. In fact, an overall solution may call for an expenditure that is out of proportion to the value or the function of the equipment requiring a protection, whereas a more economical solution may not be reliable. It is therefore necessary to assess the characteristics of the protection, with the help of experts, or turn to a reputable company that can offer adequate technical support.