This article proposes a real-time, setting-free out-of-step (OOS) protection strategy for a single synchronous generator (SG) connected to a multimachine power system. To do so, the fundamental frequency phasor of the voltage at the generator terminal is measured. It will be shown that at the point of OOS, the imaginary part of the voltage crosses the zero point and becomes negative, whereas the real part of the voltage holds a negative value. On the other hand, it will be shown that during stable power swings, the imaginary part of the voltage behaves as per an OOS event, whereas the real part of the voltage becomes positive. Therefore, this principle can be used as the criterion to detect an SG OOS. Moreover, it will be shown that the proposed principle can count the number of SG pole slip occurrences so that it can trip the generator after a certain number of pole slips. The proposed scheme is a response-based algorithm and uses only locally measured voltage at the relay location. F
Fairport, NY: Saelig Company Inc. has announced the Cleverscope CS548 Oscilloscope, a 2kV DC isolated channel oscilloscope designed to be used wherever isolation and high CMRR are needed. It improves on the previous and very successful CS448 for power electronics and high side test measurements. The CS548 is an individually isolated channel high CMRR oscilloscope with four channels that…
This paper presents a new hybrid three-phase cascaded modular multilevel inverter developed with reduced switch count for harvesting renewable energy. The basic module of the proposed inverter consists of six switches, three asymmetric dc links, and two blocking diodes. The inverter can generate six positive voltage states, which are negatively polarized by the end-side H-bridge unit. As a result, higher number of voltage levels are obtained with minimum number of switches that ensure reduced total harmonic distortion in the grid current. Additionally, the proposed inverter can operate at comparatively lower switching frequency, which decreases the switching loss. Most of the switches in each individual module conduct for a small period resulting in low conduction losses. The reduced switch count with the low switching and conduction losses increases the compactness and the efficiency of the proposed inverter. Multiple high-frequency magnetic links are utilized for the dc sources requi
LED photometry using the Paired Emitter Detector Diode (PEDD) strategy has been demonstrated to be a viable sensing method for analytical measurements. Timing of the LED discharge is one of (if not ‘the’) primary factors in this approach, and can have a significant impact on sensing characteristics, such as resolution or the limit of detection (LOD). Details of these timing implementations have not appeared in the literature thus far, making reproducibility and comparisons between systems challenging. This study investigates a number of timing implementations and demonstrates that the difference between these methods can impact resolution by up to 68%. Specifically, the three methods are based on a variety of Arduino functions and base C registry readings for the logical operations (comparison and reading the digital I/O status), i.e. (1) ‘Wiring: digitalRead(), if()’, (2) ‘C: Register, if’, and (3) ‘C: Register, switch()’. Additionally, during a deeper analysis, it was