Coupling capacitor voltage transformers (CCVT) are the predominant devices used in high voltage systems to provide scaled down voltage signals for metering, protection and control devices. The performances of these devices are subject to errors due to the transient behavior of CCVT, so that the use of CCVT digital models is essential for power systems studies in order to predict how the equipment dynamics affect protective relaying performances. In this review paper, the authors put together complete information regarding five realistic CCVT digital models available in literature and perform a detailed sensitivity analysis of their magnitude and angle frequency responses, as well as their influence on phasor estimation, distance protection, and fault location techniques.

This letter presents a practical methodology to improve traveling wave (TW)-based fault location (TWFL) on transmission lines by leveraging classical single- and double-ended TWFL functions available in off-the-shelf relays and digital fault recorders. It eliminates negative effects of uncertainties in line propagation velocity and travel time, being free of time-consuming or complicated procedures. Real TW records are studied to demonstrate that the proposed solution can improve the accuracy and reliability of TWFL estimations when uncertainties about line propagation velocity or travel time exist.