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Protective Current Transformer
Aug 14, 2018

Protective current transformers are divided into: 1. Overload protection current transformer, 2. Differential protection current transformer, 3. Ground protection current transformer (zero sequence current transformer)

The protective current transformer mainly cooperates with the relay device and provides the relay device with signal to cut off the fault current when the fault such as short circuit overload occurs in the circuit.

Road to protect the safety of power supply system. Working condition and measuring current of protective current transformer

protective current transformer

protective current transformer

Transformers are completely different. Protective transformers work only when the current is several times larger than the normal current. The main requirements of protective transformers are: 1. reliable insulation, 2. large enough accurate limit coefficient, 3. sufficient thermal stability and dynamic stability.

Protective transformer can satisfy the requirement of accurate level under rated load. The maximum primary current is called rated accurate limit primary current. The accuracy limit coefficient is the rated accuracy limit, the primary current and the rated primary current ratio. When the primary current is large enough, the core saturation does not reflect the primary current, and the accurate limit coefficient represents this characteristic. Protective transformer accuracy grade 5P, 10P, indicating that the allowable current error is 1%, 3% at the rated accurate limit primary current, and the composite error is 5%, 10% respectively.

When the fault occurs, the impulse current generates heat and electromagnetic force, and the current transformer must be protected. In the case of secondary winding short circuit, the current transformer can withstand the primary current without damage in one second, which is called rated short-term thermal current. In the case of secondary winding short circuit, the current transformer can withstand the primary current peak without damage, which is called rated dynamic stable current.

The accuracy grade 5P/10P of protection current transformer and 10P indicate that the composite error is not more than 10%.


Add: No.38 South Taoyuan Road, Yaozhuang Town,Jiashan County, Jiaxing City, Zhejiang Province, China
Contact person: Elva Zhuang&Sunny Ni
Tel:+86-573-84775555
Fax:+86-573-84776699
Phone:+86-13732570066
E-mail:
sales@great-relay.com