Research on Rates Discharge Characteristics of High Energy Density Ternary Lithium Battery

In order to study the effect of rates discharge on characteristics of ternary lithium batteries, a new type of high rate ternary lithium battery from a unit is used as the research object. The discharge test is carried out at the discharge rates of 1C, 4C, 7C, 12C and 15C on this ternary lithium battery at room temperature with high and low temperature charge/discharge test system. The test results show that the energy density under 1C rate discharge is 202.62wh/kg. Correspondingly, the energy density under 4C, 7C and 12C rate discharge is 95.17%, 93.83% and 91.79% of the value under 1C rate discharge respectively. Even for 15C rate discharge, its energy density can reach 87.15% of 1C rate discharge. During the discharge process, the temperature of the battery increased with the increase of discharge rate, and the temperature rise at 15C rate by 26 °C.

Research on 500kV Transformer on-load Tap Changer Fault Treatment and Physical Properties Testing

This article introduces the intermittent increase of acetylene content in the oil during the operation of a 500kV start-up substation of a power generation company. It is preliminarily judged that there is spark discharge in the oil chromatographic analysis and on-site partial discharge test. After returning to the factory for maintenance and internal inspection, it was found that the movable contact and the fixed contact of the selected part of the on-load tap-changer were not connected in place, which caused intermittent spark discharge and continued to increase acetylene. The problem is solved by adjusting the number of turns of the gear when the tap switch is switched forward and backward, and the transformer resumes normal operation.

Automatic Actuation of the Anti-Freezing System Using SMA Coil Springs

Studies have been actively conducted on systems that prevent the breakage of water pipes from freezing in winter. Shape memory alloy (SMA) coil springs have been used as the key components of actuators that can operate automatically by detecting the real-time outside temperature changes, but research on its use as an actuator that can operate at sub-zero temperatures is insufficient. This study proposes the anti-freezing system using Ni-44.08Ti-1.46Co (wt.%) SMA coil springs that operate near sub-zero temperatures to prevent the freezing accident of water pipes. After fabricating the SMA coil springs, the test for performance evaluation of the springs applied static load conditions was conducted on the specific outside temperature. To examine the operation of anti-freezing systems applied the SMA coil spring as an actuator, the water discharge test (WDT) was also conducted along with the computational fluid simulation. The results of water discharge measurement obtained by WDT, simulations, and theoretical equations applied to the fluid resupply system constructed were compared with each other to verify the reliability. Consequently, it was confirmed that water discharge can be automatically controlled in real time according to temperature changes of SMA coil springs in the anti-freezing system.

Lithium ferro phosphate battery state of charge estimation using particle filter

Lithium ferro phosphate (LiFePO₄) has a promising battery technology with high charging/discharging behaviours make it suitable for electric vehicles (EVs) application. Battery state of charge (SOC) is a vital indicator in the battery management system (BMS) that monitors the charging and discharging operation of a battery pack. This paper proposes an electric circuit model for LiFePO₄ battery by using particle filter (PF) method to determine the SOC estimation of batteries precisely. The LiFePO₄ battery modelling is carried out using MATLAB software. Constant discharge test (CDT) is performed to measure the usable capacity of the battery and pulse discharge test (PDT) is used to determine the battery model parameters. Three parallel RC battery models have been chosen for this study to achieve high accuracy. The proposed PF implements recursive bayesian filter by Monte Carlo sampling which is robust for non-linear and/or non-Gaussian distributions. The accuracy of the developed electrical battery model is compared with experimental data for verification purpose. Then, the performance of the model is compared with experimental data and extended Kalman filter (EKF) method for validation purposed. A superior battery SOC estimator with higher accuracy compared to EKF method has been obtained.

Influence of Corona Discharge on CaSO4 Solubility of Silicone Rubber Insulator Surface

Some studies have shown that the operating state of silicone rubber insulators is not only affected by surface corona discharge, but also different due to the surface covered with different pollutants, but few studies have linked the two. In this paper, by designing the corona discharge test of silicone rubber insulator, the output of nitric acid from its surface product was calculated, and the concentration of nitric acid under different air humidity was obtained. The solubility test of slightly dissolved salt calcium sulfate in nitric acid solution at 293.15K and 333.15K was designed to obtain the solubility of calcium sulfate at different concentrations of nitric acid at two temperatures. Finally, a quantitative analysis of the solubility of calcium sulfate on the surface of insulator FXBW-10/70 in nitric acid solution shows that the surface contamination of insulator with good hydrophobicity may be completely dissolved by nitric acid solution, but the surface of insulator with loss of hydrophobicity cannot be completely dissolved by nitric acid. This study provides a theoretical basis for the dissolution characteristics of silicon rubber insulator corona discharge on its surface soluble salt composition and provides a new idea for the influence of insulator corona discharge on its electrical properties.

The Graphene/Fe3O4 Nanocomposites as Electrode Materials of Supercapacitors

The graphene/Fe3O4 (GN/Fe3O4) nanocomposites used as electrode of supercapacitors were prepared by chemical reduction-high temperature treatment. The Fe3O4 with uniform size regularly decorate on the surface of graphene. According to the charge and discharge test, the GN/Fe3O4-0.05 electrode has the good mass specific capacitance (265.6 F/g) at a current density of 0.5 A/g. When the power density is 20.27 kW/kg, the energy density reaches 11.26 Wh/kg. Finally, the button supercapacitors were assembled used the prepared nanocomposites as electrodes. The nanocomposites exhibit stable capacitance efficiency after 100 cycles of charging and discharging. The capacitance efficiency still exceeds 80% after 500 cycles of charging and discharge, indicating that the nanocomposite has excellent cycle stability.