Experimental Study on Splitter Plate for Improving the Dielectric Recovery Strength of Low-Voltage Circuit Breaker

The low-voltage circuit breakers are widely used to protect loads in the distribution system. Interruption reliability of circuit breakers is important because they are a protective device close to the customer. In particular, the re-ignition phenomenon leads to over-current blocking failure due to the arc re-formed between electrodes despite the normal trip of the circuit breaker. In this paper, in order to improve the interruption performance against re-ignition, the dielectric recovery voltage measurement system of the circuit breaker is used and the experiment of changing the splitter plate is carried out. Two experiments are carried out by changing the splitter plate, especially changing the material of splitter plate and the number of lower plates of the splitter plate. In the case of changing the material of the splitter plate, the analysis is conducted according to the thermal conductance. In the case of changing the number of lower plates of the splitter plate, the number of plates and their spacing are variables. Analyzing the results of the dielectric recovery voltage experiment, in the initial period, copper plates have the best value that shows 102.1% improvement compared to normal and Al shows 59.8% improvement compared to normal. These increases are related to the thermal conductivity of the three electrode materials. In the case of changing the number of lower plates of the splitter plate, the 8-plates and 9-plates show 84.5% and 36.1% increases compared to normal, respectively, in the initial period. It can be seen that too many plates interfere with heat dissipation. Since this study studies performance improvement during the initial period, there is not much difference in the later period. This is consistent with the experimental results. In this study, an experimental basis is provided for the dielectric recovery strength from a low-voltage circuit breaker. It is expected that this will contribute to the research to improve the dielectric recovery capability of the circuit breaker

Circuit Model and Analysis of Molded Case Circuit Breaker Interruption Phenomenon

There are complex physical phenomena for the interpretation of a molded case circuit breaker (MCCB) in a distribution system. Most of the studies of MCCB interruption phenomena were conducted with numerical analysis and experiments. This traditional approach may help improve the performance of the MCCB itself, but it is difficult to find connectivity with other systems. In this paper, the circuit model is proposed and the interruption phenomenon of MCCB is analyzed. The interruption of the MCCB is divided into three sections to deal with physical phenomena occurring in each area. A simplified model is proposed considering the characteristics of each section. Based on this model, the circuit model is proposed. To implement the features of each section, the calculation of physical phenomena is carried out, and this is expressed in the circuit model with resistance and zener diode. Comparing the results of the simulation with the experimental results is as follows. For 7-plates (basic state), the error rate is −5.6% in section II and 16.8% in section III. For 1-plate, the error rate is 36.5% in section II and −17.0% in section III. This case shows much difference from the simplified model in this paper, resulting in the largest error rate. The 7-plates and 5-plates cases, which are available in the general MCCB owing to the shortest distance from the arc, represent a relatively small error rate. Using the proposed circuit model, it is expected that the entire system, including the interruption phenomenon, can be interpreted as a single circuit model

Analysis of Short-Circuit and Dielectric Recovery Characteristics of Molded Case Circuit Breaker according to External Environment

A molded case circuit breaker (MCCB) is one of the most important factors for safety to protect a load from overcurrent in a power distribution system. MCCB, which is mainly installed in switchboards and distribution boxes, may be affected by external temperatures and magnetic fields, but the above factors are still excluded from product standards and performance evaluation. This paper is the result of experimenting and studying the negative effects of these external temperatures and external magnetic fields on MCCB with short-circuit characteristic and dielectric recovery strength. As a result of temperature, it can be found that both short-circuit characteristic and dielectric recovery strength change linearly in accordance with the external temperature. The ratio of the values of 35 °C to 25 °C and 45 °C to 25 °C show the following results. t10, t21, and t32 are 1.58, 1.53, and 1.79, respectively, in short-circuit characteristics and ti, tm, and tl are 1.59, 1.69, and 1.53, respectively, in dielectric recovery strength. Depending on the external magnetic field, the short-circuit characteristics decreased by 8.56% only in the t21 period. The dielectric recovery strength decreases by 4.92% in the initial section (ti) and 14.45% in the later section (tl), respectively. It has been confirmed that the external magnetic field interferes with the emission of hot gas

Fast Fault Detection and Active Isolation of Bidirectional Z-Source Circuit Breaker with Mechanical Switch

In this paper, a new design is provided so that the Z-source circuit breaker with a mechanical switch operates quickly at a low-impedance fault. When the fault occurs, the Z-source circuit breaker uses an impedance network to generate forced current zero crossing on the switch. This current zero-crossing time is not sufficient when mechanical switches are applied. In addition, since the MS switch operates through the fault detection sensor, the speed is slowed down. At a slower speed, the circuit breaker may not allow fault current isolation. To solve this problem, the Thomson coil was added to the circuit. It operates immediately in a low-impedance fault without additional fault detection devices. As a result, the faster operating speed is expected to reduce the size of the Z-source circuit breaker component and the stress of the breaker. It is mathematically analyzed and derived, and verified through simulations and experiments. The main features of the proposed model are fast detection and operation, normal-state circuit disconnect, fault current limitation, and low conduction loss

Analysis of Short-Circuit and Dielectric Recovery Characteristics of Molded Case Circuit Breaker according to External Environment

A molded case circuit breaker (MCCB) is one of the most important factors for safety to protect a load from overcurrent in a power distribution system. MCCB, which is mainly installed in switchboards and distribution boxes, may be affected by external temperatures and magnetic fields, but the above factors are still excluded from product standards and performance evaluation. This paper is the result of experimenting and studying the negative effects of these external temperatures and external magnetic fields on MCCB with short-circuit characteristic and dielectric recovery strength. As a result of temperature, it can be found that both short-circuit characteristic and dielectric recovery strength change linearly in accordance with the external temperature. The ratio of the values of 35 °C to 25 °C and 45 °C to 25 °C show the following results. t10, t21, and t32 are 1.58, 1.53, and 1.79, respectively, in short-circuit characteristics and ti, tm, and tl are 1.59, 1.69, and 1.53, respectively, in dielectric recovery strength. Depending on the external magnetic field, the short-circuit characteristics decreased by 8.56% only in the t21 period. The dielectric recovery strength decreases by 4.92% in the initial section (ti) and 14.45% in the later section (tl), respectively. It has been confirmed that the external magnetic field interferes with the emission of hot gas

Analysis of Characteristics of Low Voltage Circuit Breaker by External Magnetic Field

Recently, as interest in eco-friendly distributed power has increased, studies on the improvement of the performance of breakers such as DC breakers and on the reliability of existing AC breakers have been actively conducted. To improve the performance and reliability of these breakers, this paper conducted the analysis of characteristics of a low voltage circuit breaker using an external magnetic field. In this experiment, before the current-zero point, the cut-off time to improve the breaker performance is shortened and after the current-zero point, re-ignition, which is associated with reliability, is suppressed. According to the experimental results, the short-circuit characteristics before current-zero show a significant difference of 0.13 ms in the t21 section, and the dielectric recovery strength after current-zero shows a 13.3% performance improvement in the latter half of the DRV (dielectric recovery voltage) V-t curve. This result has significant meaning because it can be easily improved under the control of the external magnetic field. Hence, it can be applied to the interruption performance improvement of breakers through detailed research in the future

Chronic Sleep Deprivation-Induced Proteome Changes in Astrocytes of the Rat Hypothalamus

Sleep deprivation (SD) can influence cognition, memory, and sleep/wake homeostasis and can cause impairments in many physiological processes. Because the homeostatic control of the sleep/wake cycle is closely associated with the hypothalamus, the current study was undertaken to examine proteomic changes occurring in hypothalamic astrocytes following chronic partial SD. After chronic partial SD for 7 days, astrocytes were prepared from rat hypothalamus using a Percoll gradient method, and their proteome profiles were determined by LC–MS/MS. Comparisons of the proteome profiles of hypothalamic astrocytes revealed that chronic partial SD increased (≥1.5-fold) 89 proteins and decreased (≤0.7-fold) 50 proteins; these changes in protein expression were validated by western blot or immunohistochemistry. DAVID and IPA analyses of these proteins suggested that SD may influence gliotransmission and astrocyte activation. PPP2R1A, RTN4, VAMP-2, LGI-1, and SLC17A7 were identified and validated as the main targets of SD in astrocytes. Our results suggest that SD may modulate gliotransmission in the hypothalamus, thereby disturbing sleep/wake homeostasis and increasing susceptibility to neurological disease; however, further studies are required to confirm whether the proteome changes are specific to SD