Research On Approaches To Retracing Measurement Value Of Leakage Current Tester

With the development of science and technology,especially modern electronic technology,all kinds of electrical and electronic devices have entered into every field of society and become the symbol of social civilization and progress and improvement of living standard.Leakage current is one of the important indicators of the safety performance of electrical equipment.The accuracy of leakage current is related to the safety of everyone's life and is concerned by the society.In the past,the equipment standard used two technologies to measure the leakage current.One is to measure the actual current in the conductor,and the two is to use a simple resistor-the capacitor network(representing the human body model)to measure the power frequency current flowing through the resistor.Along with the electronic switch technology is widely used in power supply systems and equipment,the high frequency harmonic voltage and high frequency harmonic current generated in the circuit,the International Electrical Commission IEC60990:1999 issued a domestic equivalent conversion to GB/T12113-2003 "measurement of touch current and protective conductor current law",the standard according to the human body on the leakage current response were defined three kinds of simulation the human body impedance network,three network and peak leakage current or effective value related with frequency changes and different,can scientifically reflect the human body impedance,leakage current tester is used to model the network.Because the structure of the new network is different from that of the early network,the calculation method of the leakage current is also different.Therefore,the existing calibration method is no longer suitable for the new leakage current tester.Under such a background,the calibration method of leakage current tester is studied,and a special calibration standard device is developed,which ensures the accuracy and reliability of the tester,and has practical significance for the quality and safety of all kinds of electrical equipment.The impedance simulation network of human body is fixed in the inner part of the new leakage current tester.It can not be dismantled and can not be calibrated.According to the simulated human impedance network given by GB/T12113-2003,the corresponding calculation formula is derived.The result is consistent with the transmission characteristic given by the standard,which also proves the accuracy of the derivation.In addition,the frequency of leakage current regulated by GB/T12113-2003 is as high as 1MHz.At present,the current frequency of domestic transmission is only 100kHz.In this paper,a new calibration standard device for new leakage current tester is designed to solve this critical problem.According to the actual state of leakage current measured by leakage current tester,the impedance network of simulated human body is directly evaluated by wide band current output,and the broadband current source method is proposed to evaluate the impedance network of simulated human body.Two high frequency shunts were designed,which worked with the Metrology Research Institute of China to solve the value traceability of the high-frequency shunt,and solved the problem of traceability of the broadband current source by the high frequency shunt.Finally,by comparing with the voltage source method,it is found that the consistency of the two methods is better,and the effectiveness of the wide-band current source method is verified.The main contents of this paper are as follows:(1)through the research of GB/T12113-2003,combined with the existing research results,the calibration method of leakage current tester simulating human body impedance network is put forward,and the accurate measurement network is realized.(2)in cooperation with the Chinese Metrology Institute,an experimental scheme to solve the source traceability of the amplitude value of the 100kHz?1MHz leakage current was jointly formulated.(3)according to the proposed broadband current source method,a wide-band and small current source was developed by the participating unit Changsha Tian Heng measurement and Control Technology Co.,Ltd.,and realized the standard output of DC-1MHz small current.(4)the theoretical derivation of GB/T12113-2003 provides the measuring circuit,between the input current and output current,on this basis,the use of broadband small current source body impedance network of leakage current tester was measured to test the feasibility of broadband current source method.(5)the same analog human impedance network is measured by the wide frequency voltage source method and the broadband current source method,and the consistency of the two is obtained through the data comparison.