Vector measurement units or phasor measurement units (PMU) are measuring devices for sinusoidal signals that measure their amplitude and phase position. They are used in low- voltage networks and smart grids and measure the phase angle of the low voltage at short intervals.
In electrical engineering and electronics, phasors are used for the vectorial representation of sinusoidal signals. They represent them in their phase position and amplitude and are thus frequency and phase dependent. Phasors are mathematically specified as complex quantities from which the dependence between amplitude, frequency and phase can be derived. As a simple example, consider a circuit of ohmic resistance, capacitance, and inductance that changes the amplitude and phase of a sinusoidal signal as a function of frequency. These vectorial relationships are expressed by the phasor.
In power grids and smart grids, the function of vector meters is functionally realized in stand-alone measuring devices and in monitoring systems. Vector meters are used in wide area monitoring systems(WAMS) to control and readjust amplitude values and phase positions. In modern concepts, data from phasor networks are collected and processed in Supervisory Control and Data Acquisition( SCADA).