Main Performance of Open-Type Current Transformers

Protection with current transformers is mainly used in conjunction with relay installations to provide signals to the relay installation to cut off the fault circuit in the event of a short circuit, overload or other fault on the line, in order to protect the safety of the power supply system. The working conditions of protective miniature CT current transformer is completely different from that of measuring transformer. Protective transformer only begins to work effectively when the current is several times or tens of times greater than normal.

The main requirements of protective open-type current transformers

Reliable insulation;
Sufficiently large and accurate limiting coefficient;
Sufficient thermal stability and dynamic stability.

The rated accuracy limit value primary current of a protective open-type CT current transformer can meet the requirements of the accuracy level under rated load.

The limiting coefficient is the ratio of the rated accuracy limit value primary current to the rated primary current. When the primary current is large enough, the iron core will be saturated and will not reflect the effect of primary current, and the limiting coefficient indicates this characteristic. The accuracy levels of protective open-type current transformers are 5P and 10P.

The role of open-type current transformers

Open-type current transformers used in power systems are a special type of transformer that transmits high voltage and high current information from the power grid to low voltage and low current secondary-side measuring and metering instruments and relay protection and automatic installations. They are the connecting elements between the primary and secondary systems, with the primary winding connected to the power grid, and the secondary winding connected to measuring instruments, protective installations and so on.

Open-type current transformers work together with measuring instruments and metering installations to measure the voltage, current and power of the primary system. Moreover, they work together with relay protection and automatic installations to form an electrical protection and automatic control system for various faults in the power grid.

The performance of open-type CT current transformer directly affects the accuracy of power system measurement and metering and the reliability of relay installation action.

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