Current Transformer For Folding Measurement Current Transformer For Folding Protection

The protective current transformer is mainly combined with the relay device. When the circuit has short circuit overload and other faults, it provides the signal to the relay device to cut off the fault electricity.

Road to protect the safety of the power supply system. The working condition of the miniature current transformer for protection is quite different from that of the transformer used for measurement. The transformer is only effective at several times the current which is several times larger than the normal current. The main requirements for protective transformers are: 1. reliable insulation, 2. accurate limited value coefficient, 3. sufficient thermal stability and dynamic stability.

For the protection of transformer under rated load can meet the requirements of accuracy class of one of the greatest amount of current is established that limit primary current. The accurate limit coefficient is the rated accurate limit of the primary current and the rated primary current ratio. When a current is large enough, the core will be saturated and does not reflect the effect of a current. The exact limit coefficient means this characteristic. The accurate grade 5P and 10P of the transformer are protected, which indicates that the allowable error is 5% and 10% at the rated accurate limit of the primary current.

The impact current caused by the failure of the line produces heat and electromagnetic force, and the protective current transformer must bear. In the case of two winding short circuiting, the current transformer is able to bear the first current effective value without damage in one second, which is called the rated short-time thermal current. When the two winding is short circuited, the current transformer can withstand the peak of the primary current without damage, which is called the rated dynamic stable current.

The protection current transformer is divided into 1. parts: overload protection, current transformer, 2. differential protection, current transformer, 3. earthing protection, and current transformer (zero sequence current transformer).