How far can one use electrical wires before needing a transformer?

are you at the end of the line? normally the high voltage is at the pole top - 4160 volts. then down the pole is a pole top transformer that connects to the high voltage - one wire to a hot, the other to a ground wire. the secondary of the transformer has three connections to it -
x1 - x2 - x3 -- one wire goes to the x1, ground to x2, other hot wire to x3. these wires are connected to what is known as the "crib line" which is a triplex cable that goes to the house's service lateral. Houses feed off this crib line for their house connections (the service lateral) if you are really 400 feet from the pole, the power company really should install a pole closer to your house than 400 feet! I say this because if you want, say, 200 amps at your house, then using a voltage drop formula, the secondary wire size would be immense! code says no more than a 3% voltage drop per 100 feet. normal 200 amp cable is 4/0-3 aluminum. at 400 feet to have 200 amp at your house you'd need at least 500 mcm cable. mcm is thousand circular mils - the cable diameter. 500 mcm is about 1 1/4 inch diameter. call the power co and have them install a pole and extend the high voltage to your house and put up a pole top xfmr.

North Country Tool Repair
February 2007