what should be noticed when we do the CT Ratio & Polarit

       The common method is current method. If CT and GIS of transformer bushing are tested, voltage method is needed. The wiring of the two test methods are different. When testing by current method, we must pay attention to the order of connection between primary side and secondary side. If the current of primary side is larger than that of secondary side, the connection must be made according to the figure above. If the current of primary side is lower than that of secondary side, the actual connection is opposite to that of primary side and secondary side in the figure above. 

        In short, we must connect the L1 and L2 on the instrument panel to the high current side, and the K1 and K2 will connect to the low current side. Special attention: the two remaining side of the remaining non-test winding should be short to avoid open circuit. When using the voltage method, attention should be paid to the K1 and K2 connected to the secondary side of current transformer, and the a and x will be connected to the primary side of the transformer. Special attention: At this time, the remaining non-test windings on the secondary side should be open circuit and not short-connected, which is different from the current method test and needs special attention.