Analysis of Harmonic Measurement Error Using Capacitive Voltage Transformer
Peng Qinghu · Gao dianya jishu · 2015
To study the distortion of capacitive voltage transformer(CVT) main circuit working at power frequency of its frequency characteristics and harmonics measurement, we simulated the frequency characteristic of CVTs with resonance and saturated reactor damper. Using the power quality producer, we performed the actual device experiments with two types of 110 k V CVT. The experimental results verify the correctness of simulation conclusion, and stray capacitance is also one of the reasons that affect CVT frequency characteristic. Test results show that remarkable errors in amplitude and phase exist in the measurement of harmonic through CVT. The maximum amplitude can reach two times more than the actual value in some frequencies, the minimum is only about 30% of the actual value, and the phase mutation of 120 degrees also appears in some frequencies; CVTs with the same manufacturer and type are basically identical in harmonic measurement error characteristic, conversely CVTs with the different manufacturers and types possess the different error characteristics. Finally, based on the massive application of CVTs, improvement suggestions such as measuring by capacitive voltage divider, measuring through ground loop current, using special CVT, and correcting the measuring results are proposed.