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Insulation of a wire is tested with a megger. On the whole megger testing is non destructive. What happens is a DC voltage is applied to the device or winding under test. It is an insulation test to see is the insulation has been injured in any way to cause a short circuit when normal power is applied to it. On my megger there are 3 ranges 300V, 750V, and 1000 volts. Applying the proper voltage is essential to not damaging the device you are testing. Working voltages up to 240 volts should use the 300 range. Working voltages up to 600 volts use the 750 volt range and working voltages above 600 use the 1000 volt range. As you can see if you used the 1000 volt range on a device that had a working voltage of say 24 volts you could damage the insulation just by testing it. So meggering a device is non destructive if you use the tester as its instructions tell you to.
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Why the mho relay is used in long transmission line?
as it is most affected by arc resistance....
What should be the insulation resistance in a electrical circuit?
As we know thath insulators are the materials which are mainly use to insulate any conducting body from the LIVE supply whether 3Ph or single phase, so the reristence of such an insulator should be infinity as it should be provide maximum resistance to the flow of current through it.
When doing an insulation resistance test on an electrical circuit do you test at 500v dc or 500v ac?
dc insulation test = 2 * operating voltage +1000V ac insulation test = 2* operating voltage impedance of long wires or cables make ac testing sort of impractical dc test will never be lower than 1000V
What is formula for calculation of line loss?
Line loss equations are complicated by transmission environment and temperature?Transmission env. - Include wire type, bus impedance in switching fields, etc.Temperature - Temperature can change the wire resistance and thus line loss.Electric energy is transported across the countryside with high-voltage lines because the line losses are much smaller than with low-voltage lines.All wires currently used have some resistance (the development of high-temperature superconductors will probably change this some day). Let's call the total resistance of the transmission line leading from a power station to your local substation R. Let's also say the local community demands a power P=IV from that substation. This means the current drawn by the substation is I=P/V and the higher the transmission line voltage, the smaller the current. The line loss is given by Ploss=I²R, or, substituting for I,Ploss = P²R/V²Since P is fixed by community demand, and R is as small as you can make it (using big fat copper cable, for example), line loss decreases strongly with increasing voltage. The reason is simply that you want the smallest amount of current that you can use to deliver the power P. Another important note: the loss fractionPloss/P = PR/V²increases with increasing load P: power transmission is less efficient at times of higher demand. Again, this is because power is proportional to current but line loss is proportional to current squared. Line loss can be quite large over long distances, up to 30% or so. By the way, line loss power goes into heating the transmission line cable which, per meter length, isn't very much heat.
How long does blown in insulation last?
10 years
