Isolation
Isolation is a mechanism that defeats grounding. It is frequently used with low-power consumer devices, and when electronics engineers, hobbyists, or repairmen are working on circuits that would normally be operated using the power line voltage. Isolation can be accomplished by simply placing a "1:1 wire ratio" transformer with an equal number of turns between the device and the regular power service, but applies to any type of transformer using two or more coils electrically insulated from each other.
For an isolated device, touching a single powered conductor does not cause a severe shock, because there is no path back to the other conductor through the ground. However, shocks and electrocution may still occur if both poles of the transformer are contacted by bare skin. Previously it was suggested that repairmen "work with one hand behind their back" to avoid touching two parts of the device under test at the same time.
Generally every AC power line transformer acts as an isolation transformer, and every step up or down has the potential to form an isolated circuit. However, this isolation would prevent failed devices from blowing fuses when shorted to their ground conductor. The isolation that could be created by each transformer is defeated by always having one leg of the transformers grounded, on both sides of the input and output transformer coils. Power lines also typically ground one specific wire at every pole, to ensure current equalization from pole to pole if a short to ground is occurring.
Read more about this topic: Ground (electricity)
Famous quotes containing the word isolation:
“The only happy talkers are dandies who extract pleasure from the very perishability of their material and who would not be able to tolerate the isolation of all other forms of composition; for most good talkers, when they have run down, are miserable; they know that they have betrayed themselves, that they have taken material which should have a life of its own, to dispense it in noises upon the air.”
—Cyril Connolly (1903–1974)
“One who shows signs of mental aberration is, inevitably, perhaps, but cruelly, shut off from familiar, thoughtless intercourse, partly excommunicated; his isolation is unwittingly proclaimed to him on every countenance by curiosity, indifference, aversion, or pity, and in so far as he is human enough to need free and equal communication and feel the lack of it, he suffers pain and loss of a kind and degree which others can only faintly imagine, and for the most part ignore.”
—Charles Horton Cooley (1864–1929)
“Only connect! That was the whole of her sermon. Only connect the prose and the passion, and both will be exalted, and human love will be seen at its height. Live in fragments no longer. Only connect, and the beast and the monk, robbed of the isolation that is life to either, will die.”
—E.M. (Edward Morgan)