Research On Calibration Device For Measurement Accuracy Of Digital Electric Energy Meter

Digital electric energy meter is applied to metering system of digital substation. Its structure and working principles are different from traditional electronic energy meter, which is not suitable for previous calibration method. At present, there is no comprehensive calibration device being researched. According to national standard and State Grid's enterprise standard, key technologies of calibration for measurement accuracy of digital meter are researched as well as corresponding device which can calibrate the measurement accuracy of digital meter comprehensively.Firstly, the technical specifications of the calibration device are designed according to relevant standards. Accuracy and timeliness of each error testing method are analyzed. A new error testing method based on combination of watt-second law and reference meter law is proposed, which can achieve high accuracy in a short-time test and be less affected by digital power source.As to the design of hardware, apart from basic parameters setting, digital power source can simulate many abnormal conditions in optical fiber transmission. PC software based on labview can carry out all tests required by standards automatically, quickly and conveniently. Also it can set many other conditions.Error characteristics of common energy algorithm are analyzed considering the influence of time accumulation and quantization error introduced by communication protocol which is specific in digital electric energy meter. Also many other factors are researched. Windowed interpolation FFT algorithm and numerical integration based on quasi-synchronous algorithm are researched which are used in reference energy calculation. Verified by simulation experiments, each algorithm has high accuracy and timeliness.Calibrated by China Institute of Metrology, the digital power source and the reference digital meter designed in the paper can reach the precision class up to 0.05 and have the uncertainty of 0.01%. With this device, a 0.2s digital meter was calibrated under all tests required by standards as well as several other experiments. The results show that it meets the requirement of relevant standards under all kinds of measurement accuracy experiments.