Five new electronically-controllable second order current-mode sinusoidal oscillators using three mul-ti-output operational transconductance amplifiers (MO-OTAs) and two grounded capacitors (GC) have been presented. S...Five new electronically-controllable second order current-mode sinusoidal oscillators using three mul-ti-output operational transconductance amplifiers (MO-OTAs) and two grounded capacitors (GC) have been presented. Simulation results are included to confirm the theoretical analysis based upon CMOS OTAs implementable in 0.5 μm technology.展开更多
The paper presents an economic hybrid circuit breaker for limiting and interrupting the faults in DC railways substations. For fast fault current interruption, the hybrid breaker incorporates high speed mechanical con...The paper presents an economic hybrid circuit breaker for limiting and interrupting the faults in DC railways substations. For fast fault current interruption, the hybrid breaker incorporates high speed mechanical contacts actuated by power semiconductor devices. Additionally, to avoid formation of electric arc, a commutation circuit is used to inject a counter current during fault interruption. In a real railway substation, each feeder is connected to the main DC bus through an expensive air magnetic DC circuit breaker and to an auxiliary DC bus through another expensive breaker. This leads to high cost especially in railway substation with multi feeders which are used to energize the vehicle transmission lines. In this paper, all DC breakers in DC railway substations are replaced by the suggested circuit breaker, which consists of a high speed mechanical contact with two semiconductor devices in each feeder and only one commutation circuit for injecting the counter current in all faulted feeders. The fault diagnosis is designed to detect the abnormal condition (current or voltage) in all feeders and direct the injected current from the commutation circuit to the faulted feeder only when the abnormal reaches a predetermine level. The suggested breaker is able to detect and interrupt any cascading of faults.展开更多
This study aims to evaluate the safety status of electrical installations in residential and commercial buildings within the Suame ECG strategic business unit, Ghana, focusing on compliance with international and Ghan...This study aims to evaluate the safety status of electrical installations in residential and commercial buildings within the Suame ECG strategic business unit, Ghana, focusing on compliance with international and Ghanaian wiring standards. The research assesses key factors influencing safety, including the certification of electricians, the quality of cable brands used, proper cable sizing, adherence to wiring color codes, the awareness and use of Residual Current Circuit Breakers (RCCBs), and the protection of earth electrodes. A descriptive research design was utilized, involving extensive field surveys and electrical installation audits. Data were collected using standardized tools and analyzed with SPSS software to evaluate the professional competencies of artisans and their adherence to safety standards. The findings indicate significant safety risks, with 69.7% of electricians lacking proper certification, leading to the widespread use of non-approved cable brands, improper cable sizing, and deviations from wiring color codes. Additionally, deficiencies were found in the awareness and use of RCCBs and the protection of earth electrodes. The study concludes with recommendations to enhance electrical safety, including mandatory certification for electricians, public awareness campaigns, regular inspections, and ongoing training and development programs. These measures are crucial for improving the overall safety and quality of electrical installations in the Suame area, Ghana.展开更多
为研究分合闸线圈电流波形曲线与电磁系统及机构传动系统性能之间的关系,利用磁路法分别建立了高压断路器弹簧和液压操作机构分合闸电磁系统的数学模型,通过理论和仿真研究电磁系统线圈电压、线圈回路电阻、铁芯工作气隙等参数变化对分...为研究分合闸线圈电流波形曲线与电磁系统及机构传动系统性能之间的关系,利用磁路法分别建立了高压断路器弹簧和液压操作机构分合闸电磁系统的数学模型,通过理论和仿真研究电磁系统线圈电压、线圈回路电阻、铁芯工作气隙等参数变化对分合闸线圈电流的影响。并选取带弹簧机构的126 k V高压断路器和带液压机构的550 k V高压断路器进行了电磁系统参数变化条件下的试验。仿真与试验结果表明,所建立的模型正确,能够反映电磁系统的实际运行状况,操作机构电磁系统分合闸线圈电压、线圈回路电阻及铁芯工作气隙等参数变化对操作机构动作性能产生很大影响,从而影响高压断路器分合闸动作性能及可靠性,研究结果对高压断路器操作机构的状态分析及评估具有重要意义。展开更多
文摘Five new electronically-controllable second order current-mode sinusoidal oscillators using three mul-ti-output operational transconductance amplifiers (MO-OTAs) and two grounded capacitors (GC) have been presented. Simulation results are included to confirm the theoretical analysis based upon CMOS OTAs implementable in 0.5 μm technology.
文摘The paper presents an economic hybrid circuit breaker for limiting and interrupting the faults in DC railways substations. For fast fault current interruption, the hybrid breaker incorporates high speed mechanical contacts actuated by power semiconductor devices. Additionally, to avoid formation of electric arc, a commutation circuit is used to inject a counter current during fault interruption. In a real railway substation, each feeder is connected to the main DC bus through an expensive air magnetic DC circuit breaker and to an auxiliary DC bus through another expensive breaker. This leads to high cost especially in railway substation with multi feeders which are used to energize the vehicle transmission lines. In this paper, all DC breakers in DC railway substations are replaced by the suggested circuit breaker, which consists of a high speed mechanical contact with two semiconductor devices in each feeder and only one commutation circuit for injecting the counter current in all faulted feeders. The fault diagnosis is designed to detect the abnormal condition (current or voltage) in all feeders and direct the injected current from the commutation circuit to the faulted feeder only when the abnormal reaches a predetermine level. The suggested breaker is able to detect and interrupt any cascading of faults.
文摘This study aims to evaluate the safety status of electrical installations in residential and commercial buildings within the Suame ECG strategic business unit, Ghana, focusing on compliance with international and Ghanaian wiring standards. The research assesses key factors influencing safety, including the certification of electricians, the quality of cable brands used, proper cable sizing, adherence to wiring color codes, the awareness and use of Residual Current Circuit Breakers (RCCBs), and the protection of earth electrodes. A descriptive research design was utilized, involving extensive field surveys and electrical installation audits. Data were collected using standardized tools and analyzed with SPSS software to evaluate the professional competencies of artisans and their adherence to safety standards. The findings indicate significant safety risks, with 69.7% of electricians lacking proper certification, leading to the widespread use of non-approved cable brands, improper cable sizing, and deviations from wiring color codes. Additionally, deficiencies were found in the awareness and use of RCCBs and the protection of earth electrodes. The study concludes with recommendations to enhance electrical safety, including mandatory certification for electricians, public awareness campaigns, regular inspections, and ongoing training and development programs. These measures are crucial for improving the overall safety and quality of electrical installations in the Suame area, Ghana.
文摘为研究分合闸线圈电流波形曲线与电磁系统及机构传动系统性能之间的关系,利用磁路法分别建立了高压断路器弹簧和液压操作机构分合闸电磁系统的数学模型,通过理论和仿真研究电磁系统线圈电压、线圈回路电阻、铁芯工作气隙等参数变化对分合闸线圈电流的影响。并选取带弹簧机构的126 k V高压断路器和带液压机构的550 k V高压断路器进行了电磁系统参数变化条件下的试验。仿真与试验结果表明,所建立的模型正确,能够反映电磁系统的实际运行状况,操作机构电磁系统分合闸线圈电压、线圈回路电阻及铁芯工作气隙等参数变化对操作机构动作性能产生很大影响,从而影响高压断路器分合闸动作性能及可靠性,研究结果对高压断路器操作机构的状态分析及评估具有重要意义。
