# Application of Time-Voltage Characteristics in Overcurrent Scheme to Reduce Arc-Flash Incident Energy for Safety and Reliability of Microgrid Protection

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## Abstract

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## 1. Introduction

#### 1.1. Background

#### 1.2. Literature Review

#### 1.3. Contribution of the Paper

- A novel optimization problem to present the AF severity with the optimal coordination of OCRs in DN. In this problem, additional constraints are suggested to be placed on the optimization problem in order to reduce AF incident energy. Moreover, this paper suggests a new constraint to the optimization problem to comply with the operational limitation of industrial relays. In this work, a defined region was the optimization problem with the AFIE categories. This aims to find the optimum setting of OCRs that considers the AFIE categories; definite regions and DGs would provide a significantly more secure environment for workers and equipment. The proposed new optimization problem aims to guarantee the mixed coordination between OCRs and AF in away will not affect the traditional function of OCRs by using WCOM, as described in following subsection.
- A new optimal coordination scheme of OCRs in DN that incorporates the DGs and the AF qualities for different scenarios is presented and solved by a new optimization method (WCOM) and compared to the powerful algorithm PSO.
- The tripping time of OCR installed on the DG bus is discussed by presenting a new coordination strategy (non-standard) for the OCR model. The proposed relay characteristic is compared with the traditional TCC in terms of the minimum operation time for a notable drop in the bus voltage.
- A comparative investigation is performed between the standard and non-standard techniques for OCR coordination, which does not include the AF, and the approach suggested considers the AF within the OCR coordination optimization model under different fault scenarios. This will provide the DN operators and engineers an indicator about the impact of AF on the protection and operation of power systems.
- The proposed OCR scheme approach is tested and verified by the use of ETAP industrial software, to provide sufficient analysis and prove the robustness of the new approach.

#### 1.4. Outline of Paper

## 2. Problem Description: Arc-Flash Protection

#### Calculation of the AFIE

## 3. Optimal Coordination Problem of OCRs and AFIE

#### 3.1. Formulation of OCR Coordination Problem

#### 3.1.1. Coordination Criteria

#### 3.1.2. Relay Operating Time Constraints

#### 3.1.3. Proposed Current Multiplying Setting (CMS) of Industrial Relay Characteristics

#### 3.1.4. The TMS and PS Constraints

#### 3.1.5. The Relay Constraints Considering AFIE

## 4. Addressing Water Cycle Optimization Method (WCOM) in Solving the Complex Overcurrent Relays Coordination Optimization Problem

#### Illustration of the Proposed Strategy to Reduce Arc-Flash Energy in Over Current Protection Scheme

#### Work-Flow and Procedures of the Proposed Strategy

## 5. Simulation Results and Discussion

#### 5.1. Case Study

#### 5.2. Results Analysis and Discussion

- Mode 1: the utility fed the microgrid (without DG).
- Mode 2: the utility and DGs fed the microgrid (with DG).

#### Numerical Results for the Proposed POSH and Conventional SITR Schemes

#### 5.3. Discussion and Comparison for Different Optimization Algorithms

#### 5.4. Evaluation Using the ETAP Software

## 6. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Abbreviation

DG | Distribution Generations |

DN | Distribution Network |

AF | Arc Flash |

WCOM | Water Cycle Optimization Method |

OCR | Overcurrent Relay |

PPE | Personal Protective Equipment |

CTI | Coordination Time Interval |

TCC | Time–Current Characteristic |

AFIE | Arc Flash Incident Energy |

CMS | Current Multiplying Setting |

TMS | Time Multiplying Setting |

OF | Objective Function |

OOT | Overall Operational Time |

PS | Plug Setting |

SI | Standard Inverse |

${\mathrm{C}}_{\mathrm{f}}$ | Estimation variable |

${\mathrm{E}}_{\mathrm{n}}$ | normalized of AFIE |

${\mathrm{W}}_{\mathrm{D}}$ | Operating distance |

${\mathrm{z}}_{1}$ and ${\mathrm{z}}_{2}$ | Configuration factor based on the grounded systems |

${\mathrm{I}}_{\mathrm{arc}}$ | Arcing current |

${\mathrm{G}}_{\mathrm{p}}$ | Gap distance between conductors |

${\mathrm{I}}_{\mathrm{f}}$ | Three-phase short circuit current |

${\mathrm{t}}_{\mathrm{j},\mathrm{k}}$ | Tripping time of relay j at short-circuit current location k |

W | Weight factor |

${\mathrm{t}}_{\mathrm{min}}$ | Lowest tripping time |

${\mathrm{t}}_{\mathrm{max}}$ | Highest tripping time |

$CM{S}_{min}$ | Minimum CMS |

${\mathrm{CMS}}_{\mathrm{max}}$ | Maximum CMS |

${\mathrm{TMS}}_{\mathrm{min}}$ | Minimum TMS |

${\mathrm{TMS}}_{\mathrm{max}}$ | Maximum TMS |

${\mathrm{PS}}_{\mathrm{min}}$ | Minimum PS |

${\mathrm{PS}}_{\mathrm{max}}$ | Maximum PS |

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**Figure 2.**The proposed relay coordination strategy based on OCR characteristics and AFIE categories.

**Figure 3.**The process and work-flow of the proposed protection scheme (POSH)for OCRs considering AFIE.

**Figure 7.**Convergence curves of the proposed WCOM and PSO optimization algorithms for (

**a**) SITR, Mode 1; (

**b**) POSH, Mode 1; (

**c**) SITR, Mode 2; (

**d**) POSH, Mode 2.

Parameters | Value |
---|---|

The maximum number of Iteration | 1000 |

Number of populations | 50 |

The constant of evaporation condition | $1\times {10}^{-5}$ |

Number of stream and sea | 4 |

Relay | CTR | PS | IPP (A) |
---|---|---|---|

R1 | 400/1 | 0.5 | 200 |

R2 | 400/1 | 0.5 | 200 |

R3 | 400/1 | 0.5 | 200 |

R4 | 1200/1 | 0.96 | 1152 |

R5 | 300/1 | 0.83 | 249 |

R6 | 400/1 | 0.35 | 140 |

Fault Location | Fault Current (A) | CT | PS | CMS | Relay |
---|---|---|---|---|---|

F1 | 4550 | 400/1 | 0.5 | 22.75 | R1 |

F1 | 4550 | 400/1 | 0.5 | 22.75 | R2 |

F2 | 5130 | 400/1 | 0.5 | 25.65 | R2 |

F2 | 5130 | 400/1 | 0.5 | 25.65 | R3 |

F3 | 8380 | 400/1 | 0.5 | 41.9 | R3 |

F3 | 8380 | 1200/1 | 0.96 | 7.274306 | R4 |

F4 | 8380 | 1200/1 | 0.96 | 7.274306 | R4 |

F4 | 1790 | 300/1 | 0.83 | 7.188755 | R5 |

F5 | 5130 | 400/1 | 0.5 | 25.65 | R6 |

F5 | 5130 | 400/1 | 0.5 | 25.65 | R3 |

Fault Location | Fault Current (A) | CT | PS | CMS | Relay |
---|---|---|---|---|---|

F1 | 2890 | 400/1 | 0.5 | 14.45 | R1 |

F1 | 2890 | 400/1 | 0.5 | 14.45 | R2 |

F2 | 3695 | 400/1 | 0.5 | 18.475 | R2 |

F2 | 3695 | 400/1 | 0.5 | 18.475 | R3 |

F3 | 5130 | 400/1 | 0.5 | 25.65 | R3 |

F3 | 5130 | 1200/1 | 0.96 | 4.453125 | R4 |

F4 | 8380 | 1200/1 | 0.96 | 7.274306 | R4 |

F4 | 8380 | 300/1 | 0.83 | 33.65462 | R5 |

F5 | 3695 | 400/1 | 0.5 | 18.475 | R6 |

F5 | 3695 | 400/1 | 0.5 | 18.475 | R3 |

Relay | Mode 1 | Mode 2 | ||
---|---|---|---|---|

SITR (TMS) | POSH (TMS) | SITR (TMS) | POSH (TMS) | |

R1 | 0.01 | 0.01 | 0.01 | 0.01 |

R2 | 0.127 | 0.145 | 0.147 | 0.153 |

R3 | 0.2562 | 0.185 | 0.292 | 0.199 |

R4 | 0.1805 | 0.09 | 0.239 | 0.096 |

R5 | 0.4801 | 0.22 | 0.326 | 0.223 |

R6 | 0.3846 | 1.706 | 0.436 | 1.85 |

OOT | 5.68 | 2.565 | 6.1 | 2.613 |

Relay | SITR | POSH | ||||||
---|---|---|---|---|---|---|---|---|

FCT | AFIE | AFB | EL | FCT | AFIE | AFB | EL | |

R1 | 0.023 | 1.312 | 3.14 | 1 | 0.03 | 0.168 | 1.12 | 0 |

R2 | 0.266 | 20.75 | 12.5 | 3 | 0.04 | 3.123 | 4.84 | 1 |

R3 | 0.462 | 52.79 | 21.12 | $<$4 | 0.07 | 8.97 | 8.22 | 3 |

R4 | 0.623 | 79.86 | 24.52 | $<$4 | 0.1 | 12.826 | 9.86 | 3 |

R5 | 1.17 | 195.5 | 51.15 | $>$4 | 1.18 | 29.99 | 20.03 | 4 |

R6 | 0.163 | 12.74 | 9.79 | 3 | 0.02 | 1.56 | 3.42 | 1 |

Relay | SITR | POSH | ||||||
---|---|---|---|---|---|---|---|---|

FCT | AFIE | AFB | EL | FCT | AFIE | AFB | EL | |

R1 | 0.022 | 1.5 | 3.36 | 1 | 0.03 | 0.207 | 1.249 | 0 |

R2 | 0.28 | 37.19 | 16.73 | 4 | 0.423 | 0.423 | 1.785 | 0 |

R3 | 0.527 | 80.39 | 24.6 | $>$4 | 15.25 | 15.25 | 10.71 | 3 |

R4 | 0.827 | 126.08 | 30.81 | $>$4 | 20.74 | 20.74 | 12.49 | 3 |

R5 | 1.14 | 203.68 | 52.2 | $>$4 | 31.9 | 31.9 | 20.66 | 4 |

R6 | 0.28 | 37.19 | 16.73 | 4 | 0.423 | 0.423 | 1.785 | 0 |

Relay | Mode 1 | Mode 2 | ||||||
---|---|---|---|---|---|---|---|---|

SITR (TMS) | POSH (TMS) | SITR (TMS) | POSH (TMS) | |||||

WCOM | PSO | WCOM | PSO | WCOM | PSO | WCOM | PSO | |

R1 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |

R2 | 0.127 | 0.128 | 0.145 | 0.147 | 0.147 | 0.148 | 0.153 | 0.155 |

R3 | 0.2562 | 0.262 | 0.185 | 0.19 | 0.292 | 0.295 | 0.199 | 0.2 |

R4 | 0.1805 | 0.181 | 0.09 | 0.09 | 0.239 | 0.240 | 0.096 | 0.099 |

R5 | 0.4801 | 0.485 | 0.22 | 0.225 | 0.326 | 0.33 | 0.223 | 0.23 |

R6 | 0.3846 | 0.386 | 1.706 | 1.7 | 0.436 | 0.44 | 1.85 | 1.9 |

OOT (s) | 5.68 | 5.74 | 2.565 | 2.66 | 6.1 | 6.21 | 2.613 | 2.7 |

Elapsed time (s) | 4.37 | 7.39 | 4.44 | 5.42 | 4.22 | 5.33 | 4.22 | 5.77 |

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## Share and Cite

**MDPI and ACS Style**

Alasali, F.; Saad, S.M.; El-Naily, N.; Layas, A.; Elhaffar, A.; Hussein, T.; Mohamed, F.A.
Application of Time-Voltage Characteristics in Overcurrent Scheme to Reduce Arc-Flash Incident Energy for Safety and Reliability of Microgrid Protection. *Energies* **2021**, *14*, 8074.
https://doi.org/10.3390/en14238074

**AMA Style**

Alasali F, Saad SM, El-Naily N, Layas A, Elhaffar A, Hussein T, Mohamed FA.
Application of Time-Voltage Characteristics in Overcurrent Scheme to Reduce Arc-Flash Incident Energy for Safety and Reliability of Microgrid Protection. *Energies*. 2021; 14(23):8074.
https://doi.org/10.3390/en14238074

**Chicago/Turabian Style**

Alasali, Feras, Saad M. Saad, Naser El-Naily, Anis Layas, Abdelsalam Elhaffar, Tawfiq Hussein, and Faisal A. Mohamed.
2021. "Application of Time-Voltage Characteristics in Overcurrent Scheme to Reduce Arc-Flash Incident Energy for Safety and Reliability of Microgrid Protection" *Energies* 14, no. 23: 8074.
https://doi.org/10.3390/en14238074