Protection of MV Closed-Loop Distribution Networks With Bi-Directional Overcurrent Relays and GOOSE Communications

Bostjan Polajzer,Matej Pintaric,Miran Roser,Gorazd Stumberger

doi:10.1109/access.2019.2952934

Bostjan Polajzer, Matej Pintaric + Show 2 more

Open Access

https://doi.org/10.1109/access.2019.2952934

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Abstract

This paper proposes measures to improve the protection of MV distribution networks operating with feeders in a closed-loop arrangement. Bi-directional overcurrent relays (OCRs) are discussed, the selectivity of which is achieved through the timing coordination of their operation. The classic approach is formulated as a minimization of the operating times of all the OCRs. The proposed approach enhances the selectivity by considering the maximum operating time of substation OCRs and the unwanted trips of in-loop OCRs. Moreover, the sensitivity is also increased by introducing an objective function that minimizes the pickup-current settings of all the OCRs together with their operating times. Furthermore, to fulfill the demanding requirements for operating times, variable penalties are introduced. Thus, the optimization procedure is forced towards the region with viable solutions for the optimization problem. Two variants of self-adaptive differential evolution have been used that both show better convergence when compared to the classic differential evolution. Moreover, ten mutation strategies were tested, where “rand/1/bin” showed the best results. A comparison with other methods for timing coordination shows that the proposed optimization results in a comparable value for the OCRs’ operating times. In order to further reduce the operating times, GOOSE communications between the OCRs are adopted. The proposed measures for improved protection operation are fully confirmed through dynamic simulations of the faults in the discussed 20-kV network. Moreover, the proposed protection design is already implemented and permanently operates in a 20-kV network with more than 5000 customers, whereas the field results show selective and reliable protection operation.

Highlights

One of the priorities of modern distribution networks is improved power-supply reliability
The selectivity of the substation overcurrent relays (OCRs) is achieved by considering the required maximum operating time (300 ms), while the unwanted trips of the in-loop OCRs are avoided by a simple procedure for short-circuit calculations
Adopting the GOOSE communications reduces the operating times, which was fully confirmed through the dynamic simulations of the Ph-Ph faults in the discussed 20-kV network

Summary

Introduction

One of the priorities of modern distribution networks is improved power-supply reliability. The key challenge in the realization of such a network operation is a proper protection system design, where all the modern solutions, such as the exchange of GOOSE (Generic Object Oriented Substation Event) messages among the relays, are applied in order to reach the goal of improved supply reliability. The selectivity of overcurrent relays (OCRs) is achieved by the timing coordination of their operation This can be performed using different optimization approaches [4]–[17]. A. RELAY NOTATION AND RELAY PAIRS Most of the research about the timing coordination of the operation of OCRs assumes that the OCRs are located at the network’s buses, which is not feasible in MV distribution networks. The incorporation of R9 depends on the DG capacity, which should be checked using short-circuit calculations

Methods

Results

Conclusion