New Testing Method of the Shielding Effect of Heavy Current Transformer With Shielding Coils

So far, there has not been any method that is both effective and accurate enough to test the performance of a heavy current transformer (HCT) under electromagnetic interference from adjacent bus-bars since the primary and adjacent currents are too high to reproduce in a laboratory. A new testing method termed as the “multiple-coil testing method” is presented in this paper to overcome this difficulty. By closely enwinding two coils that are connected in opposed-polarity series on the HCT, the original magnetic field in the core produced by a single external current source can more accurately be simulated. Thus, the performance of the HCT under working conditions can equivalently be tested in a laboratory. By using two pairs of such coils, which are positioned at right angles to the other pair and work independently, this method can simulate the magnetic field from multiple external current sources positioned in arbitrary manner and consequently test the performance of the HCT under electromagnetic interference from multiple current sources. This new method is both accurate and effective, and easy to implement. It can be applied to overcome the testing difficulty of an HCT in a laboratory, which particularly has shielding coils.