Propagation delay measurement and compensation for sampled value synchronization in a smart substation

Abstract

Reliable sampled value (SV) synchronization is used to ensure the reliability of protective relaying in a smart substation based on IEC 61850. In this paper, an SV synchronization method based on SV propagation delay measurement and compensation is proposed. The method does not depend on an external reference clock and has higher reliability than existing ones. The core issue in the proposed method is to measure the switching delay. The following steps are undertaken in this work: First, the composition of SV propagation delay in a smart substation is analyzed. Second, a new switch with the capability of switching delay measuring and recording is presented. Third, two laboratory tests are conducted to study the measurement accuracy of the switching delay. Finally, an SV synchronization method is presented and its application is tested on a busbar protection system to demonstrate that the proposed method can achieve SV synchronization effectively. Test results show that the measurement is sufficiently accurate for the SV propagation delay compensation. The proposed method also shows that the reliability of the protective relaying in a smart substation is significantly improved.