Primary lines, or primaries, are higher-voltage lines located at the top of utility poles, above transformers. Primaries are usually made out of copper or steel encased in highly conductive aluminum. Typical primary voltages range from 4.16 to 34.5 kV.
Secondary lines, or secondaries, are located lower down on utility poles, usually below transformers. Typical secondary voltages are between 120 and 280 volts. Although the voltage is lower, these lines can still deliver a severe electrical shock if contacted.