Developing and testing a novel busbar protection scheme for impedance-earthed distribution networks

Abstract

Busbars are one of the most crucial components in the electricity grid and, as such, must always be protected against all types of faults.
The busbar differential protection is a protection scheme typically utilized to protect the busbar system in high-voltage substations. Nevertheless, due to the vast number of substations in the distribution level and the high cost of differential busbar protection, DSOs try to implement more cost-effective protection schemes for the busbars. This includes using various communication-based protection schemes, such as the reverse-blocking scheme that Stedin implements. However, due to impedance grounding, the single-phase-to-ground short circuit current can reach small values in magnitude in medium voltage distribution grids, making detecting it more challenging for these protection schemes. That is the problem that Stedin experiences in its network.
In this thesis, a novel communication-based protection scheme is proposed as a solution to this problem. The protection scheme utilizes the IEC 61850 standard and the currently available infrastructure Stedin owns. The scheme can be considered a distributed protection scheme. The grid is modeled in RTDS, and a HiL simulation is carried out to test the protection scheme. The extensive simulations show that this scheme can detect single-phase-to-ground busbar faults in impedance earthed networks. Some limitations of the proposed scheme are also seen in the simulation results. Furthermore, a centralized approach for busbar protection is discussed. Two algorithms are developed based on GOOSE and SV messages, respectively. HiL simulations are carried out for these centralized algorithms too. The advantages and the considerations for implementing centralized protection are discussed. These findings can serve as a basis for further research for Stedin in the domain of centralized protection.