The relay coordination problem is of dire importance as it is critical to isolate the faulty portion in a timely way and thus ensure electrical network security and reliability. Meanwhile a relay protection optimization problem is highly constraint and complicated problem to be addressed. To fulfill this purpose, Harris Hawk Optimization (HHO) is adapted to solve the optimization problem for Directional Over-current Relays (DOCRs) and numerical relays. As it is inspired by the intelligent and collegial chasing and preying behavior of hawks for capturing the prey, it shows quite an impressive result for finding the global optimum values. Two decision variables; Time Dial Settings (TDS) and Plug Settings (PS) are chosen as the decision variables for minimization of overall operating time of relays. The proposed algorithm is implemented on three IEEE test systems. In comparison to other state-of-the-art nature inspired and traditional algorithms, the results demonstrate the superiority of HHO.
This paper presents the design of a calculable standard dipole antenna with a hybrid balun in the frequency range of 1 GHz to 3 GHz. A new formula of the antenna factor for a dipole antenna with a hybrid balun is derived using the power mismatch-loss concept. The antenna factors derived in this paper are in good agreement with the results calculated from S-parameters. The design results show that the calculable dipole antenna with a hybrid balun can be characterized by power mismatch-loss component factors.
This paper presents a novel forced-resonance microwave technique to detect surface cracks in metal. This technique utilizes a cutoff cavity with a control element and a voltmeter to probe for surface cracks in the metal. Crack signals are detected by using forced resonance from the cutoff cavity probe. In the absence of a crack, the cutoff cavity probe aperture with a shorting plate (short-circuit) can resonate forcefully by adjusting the control element, and the forced resonance characteristics of the cutoff cavity are then probed by a detector (voltmeter) with voltage maximized. However, in the presence of a crack, the forced-resonance cutoff cavity probe aperture, in turn, changes the resonance properties from a short circuit, and the resonance variations are then detected by the detector as the voltage varies. The validity of this method was established by comparing experimental results with theoretical values.
The purpose of this paper is to present the aperture cut-off filter for reduction of electromagnetic field penetration through a slot in conducting screen. The reduction characteristics of electric field penetration by the aperture cut-off filter are considered. In order to establish the concept of the aperture cut-off filter, the integral equation on the slot aperture field distribution is derived and solved by method of moments, and the reduction characteristics of penetration electric fields for the incident plane wave are calculated. The numerical results showed that the aperture cut-off filter for reduction of electric field penetration through the slot can be realized. To check the validity of the concept of an aperture cut-off filter and the theoretical analysis, the calculated electric field penetration of the metallic wall with narrow slot were compared with the experimental results.
This paper presents the current characteristics inside a cutoff cavity slot probe applied to crack detection using the forced resonance microwave method (FRMM). Crack detection using FRMM has two stages: preparation and detection. In the preparation stage, the current characteristics inside the probe with a shorting plate are important for determining the crack signal and detection sensitivity. The cutoff cavity probe produces a forced resonance by adjusting a control element. There are two kinds of forced resonance: series resonance (SR) and parallel resonance (PR). Four types of current characteristics are applied to crack detection using FRMM: SR, the region around SR, the region around PR, and non-resonance. These current characteristics are discussed from the point of view of current change for crack detection. The experimental results are compared with the theoretical results to check the current state inside the cutoff cavity probe.
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