Verification of measured transmission system phase angles

Measurement of power system phase angle is being studied for use in protective relaying, critical control circuits, and other applications. This paper compares phase angles measured by a synchronized measuring unit during field testing with classical theory. Power system positive sequence voltage and current phasors were recorded during testing of a new 525 kV compensated transmission system. Steady-state phase angles (δ) and magnitudes were measured relative to a satellite-based global time standard on synchronized measurement units at two substations. Phase angles were calculated using a recorded supervisory system and sending-end values of total power flow. Field measurements of the phase angle across a transmission system differed from calculations by -0.09° on average, contributing to verification of the new synchronized measurement technique