Dynamic State Estimation Based Unit Protection

The introduction of new data acquisition systems, i.e., merging units, provides more accurate data to protection schemes enabling faster and more reliable protection. This paper presents an object-oriented dynamic state estimation based protection (DSEBP) scheme on a protection unit using the measurements obtained from merging units. The DSEBP uses instantaneous measurements and adopts a detailed and object-oriented model that represents the protection zone, which may comprise two or more devices, and performs dynamic state estimation to determine whether an internal fault has occurred. The dynamic state estimation provides the best estimate of the protection zone states as well as the probability that the un-faulted protection zone model fits the measurements. When the probability drops below a certain threshold, a trip decision is issued with a user selected time delay. The DSEBP requires few settings (e.g., trip delay time, etc.) and is applicable to any combination of devices in the protection zone. This paper uses an example consisting of a transformer and a cable in a substation to substantiate the effectiveness of this method.