potential transformer (PT ratio)

Potential transformers, also known as voltage transformers (VT), are used to convert high voltages to safe levels before the high voltages or currents reach the transformers or meters. The PT ratio is the voltage ratio between the primary and secondary windings. The primary winding has a greater number of turns than the secondary winding. In North America, the PT ratio is typically chosen so that the nominal secondary voltage is 120 volts.