Piece–wise Linear Characteristic for Coordinating Numerical Overcurrent Relays

Ojaghi, Mansour; Ghahremani, Robab

doi:10.1109/tpwrd.2016.2578324

Cited by 33 publications

(22 citation statements)

References 8 publications

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“…Different types of time-current characteristics can be used, i.e., definite-time, inverse-time or custom-based, e.g., piecewise linear [31]. In the following, only the inverse-time characteristic will be discussed, which is given as…”

Section: B Time-current Characteristicsmentioning

confidence: 99%

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

et al. 2019

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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.

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Section: B Time-current Characteristicsmentioning

confidence: 99%

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

et al. 2019

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“…However, the recommended characteristic depended only on the fault current and was not tested considering the effect of DG integration. Another non-standard approach, in which a table contains fault current levels along with the corresponding operation time of the relays was presented in [22]. Using this approach, the primary operation time dependency on coordination was eliminated, but the effectiveness of the proposed approaches was not studied considering also the penetration of DG units.…”

Section: Relevant Literaturementioning

confidence: 99%

A Non-Standard Characteristic Based Protection Scheme for Distribution Networks

et al. 2018

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Abstract:The increasing number of distributed generation (DG) units in the distribution systems poses a challenge on protection systems in terms of coordination. In addition, the single characteristic based conventional protection causes an increase in the primary operation time of the relays due to the coordination between relay pairs. As a consequence, earlier studies investigated the utilization of non-standard characteristics and protection schemes in order to ease the insufficiencies of the standard approach. However, a commonly accepted protection approach that mitigates the effect of DG while providing lower primary operating time by levering the benefits of the non-standard protection strategy has not been developed so far. In order to overcome the aforementioned drawbacks of traditional protection, this paper firstly introduces a non-standard characteristic and then proffers an unconventional protection strategy, which utilizes a double characteristic.The suggested protection approach is tested on the IEEE 14 Bus distribution system including synchronous generator based DG connection. The results show that the proposed characteristic and protection scheme are able to provide a substantial decrease in the operation time of the relays while meeting the coordination requirements.

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“…• Multifunctionality: their capability to carry out extra tasks such as the fault recording, event recording and so on. • Flexibility: their capability to define arbitrary time-current characteristics (TCCs) by the user [7] and so on.…”

Section: Introductionmentioning

confidence: 99%

“…Lower operating times in comparison with SCs were achieved in [25] by introducing a flexible NSC based on a logarithmic function, however, this NSC is not usable by the existing industrial OCRs, too. With the aim of preserving a constant CTI between the main/backup relay pairs in the whole fault current range, a piece-wise linear (PWL) characteristic was introduced in [7]. This characteristic curve is formed by joining successive straight lines and can be easily presented in tabular format to be exactly set on the existing industrial relays.…”

Section: Introductionmentioning

confidence: 99%