Primary lines, or primaries, are higher-voltage lines located at the top of utility poles, above transformers. Primary wires are typically copper, aluminum and aluminum with steel-reinforced conductors. Some are coated with a protective covering but should not be considered insulated. Typical primary voltages include 7,200 volts single phase and 12,500 volts three phase.
Secondary lines, or secondaries, are located lower down on utility poles, usually below transformers. Typical secondary voltages are between 120 volts to 480 volts. Although the voltage is lower, these lines can still deliver a severe electric shock if contacted.