How can I work safely with a live electrical current?

Even de-energized power lines can be hazardous, owing to the complex nature of the electrical system. Even though one circuit may be ostensibly shut off, that circuit may still be conducting electricity from an interconnection with other live circuits. Thus, care must be taken to ensure that all possible sources of power to a circuit are removed. This can be especially dangerous when transformers are involved in the connection to another circuit, or one circuit is fed by more than one other circuit. For example: A higher-voltage distribution level circuit may feed several lower-voltage distribution circuits, using step down transformers. A step down transformer can also act in reverse as a step up transformer. If the higher voltage circuit is de-energized so it can be worked on, but any one of the lower-voltage circuits connected to it via a transformer remains energized, the transformer will convert the power in the lower-voltage circuit back to the higher voltage, and the higher voltage circuit will remain energized. This is known as backfeed. Another problem can arise when de-energized wires become energized through electrostatic or electromagnetic induction from energized wires in close proximity. One precaution against this is to connect all the wires in a circuit to each other and to ground before working on it, hence the saying, "if it's not grounded, it's not dead."