Signal phase shifting during synchrophasor measurements

In power systems applications, digital relaying algorithms are using samples taken from measured alternating current signals to determine characteristics that describe quantitatively the power system state. The most frequently used values to describe the signals are the magnitude and phase angle of the sinusoidal representation in time of the measurement. The signal samples are processed in discrete mode, and the results are influenced by the hardware and algorithms used to obtain them. When the measured phase angle contains errors, they translate into a phase shift of the phasor representing the signal. For synchrophasor applications, significant phase shift can be introduced during the process of calculating and transmitting the information. Some of the causes of signal phase shifting during synchrophasor measurements are described, and the case is made for sample level data transmission as a possible solution to precise phase angle calculations. An alpha-plane differential protection system is investigated to test the synchronization between the sampled signal phase angle and the calculated phasor angle using sample level data transmission