Leakage Current Data Acquisition System For Flashover Tests Of Insulators Under Iced And Contaminated Conditions

The electric systems are seriously threatened by flashover of iced and contaminated insulators, which are caused by leakage current (LC). The change and development of LC is one of the main decisive factors of flashover. Inspecting the change and development of LC during the icing flashover and contamination flashover can help to analyze the mechanics of insulators and the developing process of arc during the flashover, which is the foundation of the physics-mathematic model of insulators' flashover. Therefore, LC data acquisition (DAQ) system for flashover tests of insulators under iced and contaminated conditions has not only an academic significance, but also a remarkable value in engineering.Based on the previous achievements home and abroad, this paper adapts LabVIEW to design the DAQ system of LC during the icing flashover and contamination flashover by means of virtual instruments. And the author designed hardware circuit and software, simulated and tested the system.For hardware circuit, current sensors are developed respectively when measuring AC and DC, and realize the measurement of LC from 0.1mA to 1A in combination with the self-designed amplifications system. According to the on spot conditions, lowpass filter, which can effectively restrain the high frequency noise, and a protection system, which can protect the DAQ system from overvoltage and overcurrent, are designed and developed. The selection principles of DAQ card are proposed on the basis of analyzing the LC frequency characteristics.A common DAQ card can be used on laboratory virtual instrument engineering workbench through designing the external interface between LabVIEW and common date acquisition card on the software design. Big capacitance data are analyzed and disposed: the optimum different amplification ratio currents merged calculation is realized; pulse current is judged and pulse number is counted; stored charge and phase difference between voltage and current are calculated; data flow and step length are adjusted.The insulators LC measurement results during flashover process in the multi-function artificial climate chamber of Chongqing University indicate that the acquisition and logging of iced and contaminated insulator's LC and partial arc exactly.