Power System Protective Functions Performance Over an Ethernet-based Process Bus

The paper presents the impact of the variable time delay of data samples on commonly used protective relaying functions. Based on the results, the case is made that current solutions that rely solely on the performance of the communications media are not providing sufficient flexibility for wide acceptance, and that the problem is not solved, only masked by the increased data rate. The paper shows that a newly proposed algorithm making use of GPS time tagging and adaptive filtering is capable of overcoming data transmission delays and provides excellent performance where conventional solutions fail. The performance of overcurrent, impedance and differential protective functions over an Ethernet process bus are compared using a power system model that integrates the protection and communications components.