No abstract

No abstract

No abstract

SUMMARY To block auto‐reclosing operation for permanent earth faults on extra‐high‐voltage transmission lines, an accurate numerical algorithm is developed in this paper. The earth fault location and its nature (arcing or arc‐less) are estimated, only using the sequence quantities of the local terminal and their harmonics. The proposed algorithm calculates the amplitude of arc voltage and compares it with a given threshold value; then, decision is made if it is transient or not. A square wave arc model is considered to represent the long electric arc in the free air. One main contribution of the algorithm is its independence from the remote terminal information such as phase difference and infeed current. The successful simulation results using the square wave and dynamic arc models show that this simple and powerful algorithm can be effectively utilized for implementing a single‐pole auto‐reclosing scheme. Copyright © 2012 John Wiley & Sons, Ltd.

No abstract

No abstract

Summary According to IEEE std. 1547, islanding mode is “a condition in which a portion of an Electric Power System (EPS) is energized solely by one or more local EPSs through the associated Point of Common Coupling (PCC) while that portion is electrically separated from the rest of the area EPS”. Therefore, the dynamic instability due to islanding may result in power swing and finally loss of synchronism. Hence, many studies have been done for islanding detection and disconnection of distributed generation (DG) in an EPS. But, these conventional methods eventually lead to the disconnection of the DG units. To improve DG dynamic stability, superconducting magnetic energy storage (SMES) can be used effectively, because SMES have a high‐energy density and fast response. This paper proposes a new method to damp the power swing after DG islanding and to maintain synchronism conditions based on SMES. Hence, the disconnection of the DG units is not required. Also, new controllers are developed for SMES including voltage source converter (VSC), and DC‐DC chopper. The controller structures of VSC and DC‐DC chopper are of PI and fuzzy logic‐based type, respectively. Superconducting coil charging is controlled by the DC‐DC chopper. SMES sizing is performed, based on power swing equations. Hereupon, dynamic load model is considered. Performance of the proposed method is evaluated by defining 12 scenarios such as strong and weak networks with load changing simulated in PSCAD. Simulation results show that the islanded DG stabilization (IDGS) method has good performance to maintain stability margin in a weak network.

No abstract