۱- Introduction

۲- Problem formulation

۳- Case studies

۴- Validation of the proposed algorithm in the laboratory

۵- Conclusion

References

Abstract

Relay coordination ensures the appropriate isolation of healthy feeders from the faulty areas in a power system. The dynamic nature of renewable sources such as wind generators (WGs) can create variations in fault levels which affect the relay settings. This causes coordination problems, which can lead to the faulty operation of overcurrent relays (OCRs). The settings of the relay need to be modified appropriately in line with the variations of fault levels, which in turn change with the wind dynamics. As a solution, wind forecast based technique for the coordination of the OCRs in wind-integrated substations is suggested in this work. In the proposed algorithm, wind speed and its direction are predicted and the settings of the relay are predetermined using an optimization technique. This reduces the computation time required for the algorithms in the current period. The algorithm is implemented in the modified IEEE 9-bus system with wind farms and also in a typical wind-integrated substation. Further, it is validated through an experimental setup in the laboratory. The results were found to be promising and the algorithm can be applied to any substations integrated with wind farms for avoiding relay mal-operations.

Introduction

Wind power generation is emerging as the fastest developing technology providing the largest share of the distributed generations. The total installed capacity of power generation from the wind has been increasing annually at an average of about 20% across the world [1,2]. The integration of wind farms with power networks is intermittent, according to the operating conditions of the WGs [3,4]. Wind farms are usually connected to the distribution feeders and then integrated into the grid. The most commonly used protection scheme for the feeders is the inverse type of overcurrent protection. The OCRs in the distribution feeders should be coordinated with their backup relays in the main feeders which connects the distribution feeders to the grid [5,6]. The settings of the OCRs are fixed at the rated capacities of the connected load and the wind farm. The penetration of wind farms into the power grid changes the conventional distribution system’s short-circuit power causing malfunctions and coordination problems in OCRs, as reported in [7]. Therefore, the settings of the relays need to be modified according to the various operating condition of the WGs. The methods commonly adopted to determine the relay settings are the conventional approaches and optimization techniques [8]. The conventional method is to predetermine all fault currents during abnormal conditions and system contingencies.