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This paper investigates the influence of the loss distribution and magnetic saturation on the efficiency performance, which includes the location of maximum efficiency point, the size of high‐efficiency region and the value of maximum efficiency, for an interior permanent magnet synchronous motor (IPMSM). The loss expressions considering magnetic saturation are first proposed and then the efficiency‐losses function model of the IPMSM is constructed. The efficiency performance of the motor is analyzed quantitatively. The general principle is summarized including adjusting the location of maximum efficiency point, expanding the size of high‐efficiency zone and improving the maximum value of efficiency from the perspective of loss distribution and magnetic saturation. Two IPMSMs with different magnetic circuit characteristics are designed to verify the correctness of the analytical method by finite‐element analysis (FEA). Finally, prototypes are manufactured for the experiment and measurement results are given for validations. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper proposes a controller for single‐phase synchronous inverters (SSIs) that was designed to stabilize the performance of a grid while providing overcurrent protection during the occurrence of a fault. The proposed controller for an SSI eliminates the multiple feedback control loops consisting of voltage and current controllers under normal conditions to avoid the instability attributed to them. To output the designed voltage precisely calculated using the core circuit, including a swing equation and speed governor, we employ the latched limit strategy for the overcurrent protection, which is combined with a proportional resonance current controller. Numerical simulations and experiments demonstrated that the proposed controller provides the designed performance while ensuring overcurrent protection during normal operation. © 2023 The Authors. IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

We developed a novel artificial line circuit that compensates for the time delay of the transient recovery voltage (TRV) for a short‐line fault (SLF) interruption test and an analysis system that automatically extracts each parameter on the SLF line characteristics from the measured waveform with high precision. This new circuit and system can drastically improve the time efficiency for the adjustment and calculation of the prospective line‐side TRV condition, which is carried out before the main test, as compared to conventional methods. We also investigated the effect of the injection current and current transformer (CT) characteristics on the SLF line characteristics. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Residual current circuit breakers (RCCBs) are used to provide electric shock protection, initial and periodical verification is necessary to check the effectiveness of RCCBs. This paper presents an auto‐monitoring system with simple application circuit and low power consumption, which can test the function of the current transformer, silicon controlled rectifier (SCR), tripping solenoid, controller and other components of the residual current circuit breaker (RCCB) periodically. This test can be completed without disrupting power to the load or compromising normal function of the RCCB, and power denial or visual alarm can be provide after a fault is detected. A simulated residual current is generated periodically, and the response of these components is monitored by the system for functional verification. In this system, the signal that triggers the SCR is limited near the end of the positive half cycle of the hot line under the test mode, in accordance with the tripping characteristic of the RCCB, the functional verification will not disrupt the power to the load. Under the work mode, the signal that triggers the SCR is consistent with the tripping signal of the RCCB controller, guaranteeing the normal function of the RCCB. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Selection of current transformers (CTs) must be done carefully to ensure protection, control, and measuring systems function correctly. Some of the conventional CTs on medium voltage (MV) switchgear in nuclear power plants (NPPs) perform poorly due to accuracy errors and saturation. This paper suggests the use of electronic current transformers (ECTs) as a solution. Simulations were done on a 13.8 kV switchgear using electromagnetic transient program restructured version (EMTP‐RV) software to compare the performance of conventional CTs and ECTs under high fault currents. It was found that ECTs show significant improvement in performance with the secondary current output of 97.37% and eliminate saturation even in systems with high symmetrical and asymmetrical short‐circuit currents. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The metro stray current leaked during the subway operation causes the nearby earth surface potential to change, so that the various neutral‐grounded transformers to be at different earth surface potentials, resulting transformer DC bias. In order to analyze the influence of metro stray current on transformer DC bias, the polarization potential monitoring data in metro traction power supply system and neutral point current of nearby transformer were compared, and the positive correlation characteristics between the two were pointed out. By studying the stray current leakage reason in the metro traction power supply system and the circulation path causing transformer DC bias, the mechanism of the transformer DC bias under the subway operating environment was revealed. Based on the discrete model of the stray current distribution, considering the mechanism of stray current on DC bias, the equivalent resistance model of the transformer DC bias caused by metro stray current was built with double‐end power supply environment. Then the calculation formula of transformer neutral point current changing with subway operating conditions was derived, the numerical calculation of DC bias current of transformer caused by metro stray current was realized. The validity of the proposed model was verified by current distribution, electromagnetic field, grounding and soil structure analysis, the simulation results showed that the proposed model can calculate the stray current distribution and the nearby transformer DC bias current with high accuracy, which provided a quantitative analysis method for studying the correlation between metro stray current and transformer DC bias phenomenon. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This article proposes a powerful ultra‐high‐speed technique for earth fault distance protection of double‐circuit power transmission lines. The proposed technique uses the zero and positive sequence of the current signals. The technique presents a discriminating method based on the appearance of zero sequences, the zero sequence magnitude, and the time arrival instants of zero and positive sequence at the relaying point. The suggested technique consists of three stages. Stage 1; the polarity technique, which is designed to detect and classify faults within the protected zone. Stage 2; the ratio technique, which is designed to identify in which circuit the fault is involved. Stage 3; it is employed to calculate the distance of faults. Extensive numbers of simulations were conducted to test the action of the proposed technique. Results show that the technique provides a speed, secure, and dependable protection technique of double‐circuit transmission lines even for remote fault, high resistance fault, and a low inception time fault. They also avoid the unbalanced load‐switching effect and the current transformer (CT) saturation problems. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

We have observed and recorded the neutral current of a 500-kV transformer at a substation in the Chubu region since 2008 in order to detect electromagnetic anomalies associated with earthquakes. In this study, we could not find any particular anomalous change of the neutral current before and after earthquakes (e.g., for the Suruga Bay Earthquake of August 11,2009). However, from the results of a quantitative analysis between geomagnetic field data and neutral current data, we would be able to investigate the underground electric conductivities near the substations. It would be possible to monitor changes of subsurface electromagnetic structure before and after earthquakes. [ABSTRACT FROM AUTHOR]