Installation of zero sequence current transformer and its difference from ordinary current transformer

- Apr 06, 2019-

The basic principle of the zero sequence current transformer is the same as that of the ordinary transformer. The main difference is that the method is different. The zero sequence current transformer is used to detect the zero-sequence current. Generally, all three live wires pass through the inner hole of the transformer, and the three-phase current is measured. Vector sum, that is, zero sequence current.

The characteristics of the zero-sequence current determine that the primary current of the zero sequence current transformer is very small under normal conditions, but under abnormal conditions, the zero-sequence current will also be large. This requires a wide measurement range for the zero sequence current transformer. Therefore, zero-sequence transformers typically allow for a large multiple of overload, which is reflected by the "accuracy limit factor".

Since the zero sequence current transformer usually passes through three live wires, the inner hole of the zero-sequence transformer is larger under the same primary current. “Inner hole diameter” is an important indicator of zero-sequence transformers. When ordering, it should be noted. Zero-sequence current transformers are divided into two types: integral and open, and their installation methods are different.

The installation of the integral zero sequence current transformer is carried out before the laying of the cable, and the cable is passed through the transformer. The open-type zero sequence current transformer is not limited by the laying of the cable. Remove the transformer connection tab, loosen the two hexagon socket bolts on the top of the transformer, put the transformer on the cable, and wipe the contact surface. Clean and thinly apply a layer of anti-rust oil. After tightening the two parts of the transformer, screw the hexagon socket bolts. The two parts of the transformer should be aligned to avoid affecting performance. Finally, the gusset is