Circuit breakers are opened at natural current zero. But there is a transient
phenomenon called Restriking Voltage (RV) which appears across the circuit
breaker contacts at the instant of arc being extinguished. The value of the RV can be double that of normal operating voltage, and its value depends on various uncertain factors like power factor, circuit conditions, current asymmetry and armature reaction. The knowledge of RV helps in deciding the circuit breaker rating. In the paper, “Statistical Evaluation of Restriking Voltage Characteristics Using Monte Carlo Simulation”, the authors, Atul Koshti, L D Arya, Rajesh Ahirwar and Manoj Gupta present a statistical methodology for evaluating the severity of RV and Rate of Rise of Restriking Voltage (RRRV), using a 132 kV system.

Micro Electro Mechanical Systems (MEMS) are tiny micromachined systems (measured in microns) that are typically arranged on small silicon chips and are used in automotive, civil, mechanical, biomedical and communication engineering. In the paper, “Simulation and Analysis of MEMS Cantilever Sensor for Tuberculosis Detection Based on Capacitive Sensing Readout Method”, the authors, P Sangeetha and A Vimala Juliet, present a biomedical sensor, in which the capacitive sensing aspect is utilized to indirectly find the mass adsorbed onto the MEMS device. This sensor has application in medical diagnosis and food control.

Metaheuristics optimization algorithms come from the capability of emulating the best features of biological systems, namely, selection of the fittest and adaptation to the environment. Cuckoo search algorithm is one such metaheuristic optimization algorithm and is based on the obligate brood parasitic behavior of some Cuckoo species in combination with the Levy flight behavior of some birds and fruit flies. The paper, “Cuckoo Search Algorithm: Basic Concepts, Variants and Applications – A Review”, by Mridul Chawla and Manoj Duhan, describes the basic concepts of Cuckoo Search (CS) algorithm its applications in different optimization problems in various fields of science and engineering. It is showed that the CS algorithm is superior to other metaheuristic algorithms and has the potential for solving complex real-world problems.

In applications like streaming video, real-time navigation and medical imaging, Printed Dipole Antenna (PDA) is used due to its advantages in terms of weight, size, aerodynamic drag, ease of fabrication, cost, etc. Yet it suffers from the inherent disadvantage of incompatibility with wideband operation. In a PDA, two arms are printed on opposite surfaces of a dielectric sheet. In the paper, “Printed Dipole Antennas with Shaped Ground Plane Used to Enhance Impedance Bandwidth”, by R P Ghosh, K Patra, B Gupta, P P Sarkar and S K Chowdhury, two novel printed dipole antennas are fabricated and tested. Measured radiation patterns and gains suggest that these antennas are likely to find widespread use in GSM and CDMA mobile communications.

A single line to ground fault in a distribution system causes very low fault current, which in turn causes difficulty in identifying the faulted line in an ungrounded system. In the paper, “Identification of Faulted Distributed Line in an Ungrounded System”, by M Upender Reddy, M Surender Reddy and Vasam Suresh, the methodology of identification of faulted line is presented using thyristor grounding method. The effectiveness of this method is verified by theoretical analysis and simulation results. This method is also applicable for resonant grounded and high resistance grounded systems.

-- MSR Murty
Consulting Editor