| What is a good insulation? This occurs when an electric wire of a motor, generator, switch, transformer or cable is carefully covered with some form of electrical insulation. The copper or aluminum wire is a good conductor and gives power to the equipment, while the insulation is just the opposite of a conductor, ie it must resist the current and keep it in its path along the conductor. could say that the electrical insulation is similar to a pipe with water. The pressure that gives the water pump, causing water to flow along the pipe, and if it had a leak would lose both fluid and pressure. In electricity and applying the "law of Ohm, the voltage is similar to pressure the pump has on the line. In other words, the voltage causes electricity to flow along copper wires. As the pipe water exerts a certain resistance to flow, isolation exercises this resistance, but it is much smaller along the wire. Ohms Law: V = I x R applying Ohms Law to the wire, we will have a lower resistance of the wire, will have more power with the same voltage. It is important to note that no insulation is perfect (his strength is not infinite), so that a certain amount of electricity flowing along the insulation through the earth. This stream may be millionths of Amper, but should be measured with good insulation test instrument, such as Megohmmeter, popular-ly known as "Megger". In short, good insulation is that it does not deteriorate with increasing voltage and hence current, obtaining a high resistance, which must be maintained over time. This is displayed to make periodic measurements and studying the trend that causes insulation deterioration.
 Possible Risks to the isolation Among the factors that deteriorate the insulation, could include mechanical damage, vibration, heat, excessive cold, dirt, oil, corrosive fumes and moisture. To varying degrees, these elements are enemies of isolation, and combined with existing electrical stress. As chip or develop cracks in the insulation, moisture and foreign materials penetrate causing an easier path for current leakage, resulting in less resistance to that point. Once you start this deterioration of insulation, different enemies tend to help each other and allow excessive current through the insulation.
In general, the insulation resistance drop is a gradual process. If we make periodic measurements with a Megger designed for predictive maintenance or processing of isolation, we can react quickly and make a planned maintenance. Otherwise, insulation losses, endanger people and equipment, which can burn. We could then conclude that "it was a good isolation becomes a dangerous driver." Taken from ElectroIndustria.
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