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Xu T.,XJ Electrical Co. | Wu Y.-X.,Chongqing Electric Power Company | Zhang H.-C.,China National Testing Center for Relay Protection and Automation Equipment | Yu Z.-H.,XJ Electrical Co.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

This paper analyzes several existing problems on the switching power supply for the relay protection in the actual running. According to the working principle of switching power supply, it makes an analysis of the following two malfunction phenomena: 1) after inputting power fluctuations, the switching power supply will stop running; 2) too large switching power supply start-up current will lead to the power supply overload alarm. This paper reproduces the above two malfunction phenomena, and studies the causes: 1) when not taking account of the discharge of protection circuit delay in the designing stage, the rapid on-off input voltage power supply will cause the disoperation of under-voltage protection; 2) two low start-up threshold will cause the too large start-up current. This paper makes a contrast test on the improved switching power supply with the original one. Source


Guo W.,XJ Electrical Co. | Zhang H.-C.,China National Testing Center for Relay Protection and Automation Equipment | Yu Z.-H.,XJ Electrical Co.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

This paper discusses one calibration system for electric transformers with analog output on the condition that the traditional calibrating method is not suitable for testing optical electric transformers. The standard conventional transformer is needed for the calibration of the electronic instrument transducers. The output of the standard conventional transformer is converted by the standard signal changer equipment. Then the converted signal is compared with the test signal. At the part of the calibration system, the source standard and analyzing of error are discussed. The max error of this calibration system is only 30% of the tested electric transformer's error. At last, this calibration system has been successfully used to test and calibrate the performance of the optical electric transformer with analog output developed. Source


Wang D.-G.,XJ Group Corporation | Zhang H.-C.,China National Testing Center for Relay Protection and Automation Equipment
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

The field experiment of the wind generator low voltage ride through is difficult to achieve. In order to accurately analyze the characteristic of low voltage ride through of doubly-fed wind generator, it is necessary to conduct a simulation analysis. Based on the basic principle of doubly-fed wind turbine in wind power generation system, the dynamic mathematical model of the unit is constructed, and a simulation model of the doubly-fed induction generator and control system is established using simulation platform of Matlab/Simulink. Simulation and analysis of doubly-fed wind turbine when the voltage drops by 50% are conducted, and the influence on the wind turbine when power grid falls is analyzed. The results show that wind turbine generator is influenced strongly by the fault when the network voltage falls as well as when it recovers. Source


Zhang H.-C.,China National Testing Center for Relay Protection and Automation Equipment | Ma C.-Y.,Zhengzhou Railway Vocational and Technical College | Li Q.-X.,China National Testing Center for Relay Protection and Automation Equipment | Feng J.-T.,China National Testing Center for Relay Protection and Automation Equipment | Chen M.,China National Testing Center for Relay Protection and Automation Equipment
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

The work environment for solar photovoltaic power generation is quite bad, and the index of safety performance of grid photovoltaic (PV) power inverter, which is an important part of the photovoltaic power generation system, must meet the technical requirements in all kinds of harsh dry, cold, and humid environment. In order to assess the safety performance of the inverter in environment, environment test platform was built; the requirements for standard low temperature, high temperature, and humidity as well as their difference at home and abroad were studied; through an experiment, the working situation of inverter in different temperature was studied, and the temperature rise of key components was monitored. Test results show that cold start and dry continued operation can provide a reasonable and harsh assessment of the safety performance of inverter. Source

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