Zhuhai, China
Zhuhai, China

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Qian Y.,Zhuhai XJ Electrical Co. | Huang W.,Zhuhai XJ Electrical Co. | Li D.,Xi'an Jiaotong University | Zhang H.,Xi'an Jiaotong University | And 2 more authors.
ICHVE 2016 - 2016 IEEE International Conference on High Voltage Engineering and Application | Year: 2016

The compact design has become the development direction of power distribution switchgear equipment. As a key element of the power distribution switch, the electric field of high voltage bushing was concentrated. In order to enhance the overall reliability of the distribution switchgear, the insulation structure of the bushing needed to be optimized. This paper constructed the three-dimensional finite element model of a certain type of 10kV distribution switchgear. Simultaneously considered the uniform breakdown field strength and engineering breakdown field intensity of SF6, determined the upper and lower limit of control field are 8850V/mm, 6500 V/mm as 1 minute power frequency withstand voltage of 42kV. The dielectric parameters of the switchgear were tested, then the electric field distribution inside the switchgear was simulated in finite element method(FEM), found that electric field was concentrated in these regions which were the air gap between bushing and flange, air gap between bushing and box and air gap between the central conductor limit and porcelain. Filling with semi-conductive adhesive, increasing the chamfer radius of conductor limit and using semi-conductive coating were adopted respectively in switch insulation structure optimization. The electric field distribution after optimization was simulated in FEM, results showed that electric field intensity in the previous concentrated area has lowered than the control field, the overall insulation reliability of power distribution switchgear has improved. © 2016 IEEE.

Ji X.,Shandong University of Science and Technology | Zhang W.,Zhuhai XJ Electrical Co. | Yu Y.,Shandong University of Science and Technology | Liu Q.,Shandong University of Science and Technology
Journal of Electrical Systems | Year: 2015

As an effective measure to improve electricity supply reliability, loop-closing operation is widely used in distribution network. Due to various distributed generation were involved into distributed system, problems such as circuit breaker overcurrent may arise if loop-closing and DG status were not well coordinated. In this paper, a new loop-closing control model which including distributed generation is proposed, and the genetic algorithm with diversity control approach is used to solve the problem. A typical case with two feeders and three distributed generations is used to illustrate the performance of the proposed method. © JES 2015.

Chang Z.,Xi'an Jiaotong University | Song G.,Xi'an Jiaotong University | Wang X.,Xi'an Jiaotong University | Guo S.,Zhuhai XJ Electrical Co. | And 2 more authors.
China International Conference on Electricity Distribution, CICED | Year: 2016

Fault characteristics of inverter interfaced distributed generator (IIGD) are determined by its grid-side converter. To deduce the fault current of IIDG is to analyze the current response under the action of grid voltage sags. To enhance the low voltage ride through (LVRT) ability of IIDG when asymmetric fault occurs, the dual current control strategy is widely used. In this paper, the positive and negative sequence current expressions were deduced based on the dual current control strategy and the influence factors were analyzed based on the expressions. When the amplitude of the fault current is higher than the maximum value of the converter can transfer, a new fault current calculation method was proposed. Theoretical analysis and simulation on PSCAD verified that the d-axis components of positive and negative sequence current meet second order response and the q-axis components are zero. The steady-state value of positive and negative sequence current is determined by the unbalance degree of grid and the transient process of fault current is determined by the control parameters of the grid-side converter. The conclusions are of great significance to relay protection of the grid with HDG. © 2016 IEEE.

Huang W.-J.,Zhuhai XJ Electrical Co. | Qian Y.-C.,Zhuhai XJ Electrical Co. | Lu Z.-L.,Beijing XJ Electrical Co.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

In the open-loop distribution network, the reliability can not be increased and the DG can not be connected better. However, in the closed-loop distribution network, the faulty line section can be isolated automatically, the normal line section can be recovered rapidly, and it needs not outage in non-fault zone. So, the civil line and industrial line which form a closed-loop system can improve the utilization rate of equipment and the voltage qualification rate by loads complementary. The maximum short-circuit current value of faulty line is similar between the closed-loop system and the open-loop system, but short-circuit current flows through more lines. The paper proposes the centralized protection to solve the protection problems in the closed-loop operation system. The new distribution network planning principle of using typical connection mode and planning according to the partition, section, load density and load characteristics is given.

Xiao D.-Y.,Southwest Petroleum University | Tan W.-B.,Zhuhai XJ Electrical Co. | Zhang W.,Zhuhai XJ Electrical Co.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2014

To solve the problem of asynchronous frequency-fixed and sampling system's complex computation and weak real-time for power system frequency measurement, a practical real-time frequency measurement algorithm is proposed. This method is based on the interpolation principle of periodic zero-crossing point, the frequency estimated value is calculated by digital filtering of FIR band-pass for A/D sampling discrete sequence and by interpolating for adjacent zero-crossing point with the same direction. The signal under test in power system is simulated and vertified under three different circumstances: excluding harmonic, including second to sixteenth harmonic and the random noise. The simulation result is compared with that of Discrete Fourier Transform (DFT) method. The result shows that this method is superior to DFT in anti-interference and measurement accuracy, it can satisfy the requirement of frequency measurement for power system due to its simplicity, strong practicability, high instantaneity and measurement accuracy. ©, 2014, Power System Protection and Control Press. All right reserved.

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