Electrical isolation and state requirements for core balanced current transformers

- Jun 26, 2019-

When the core balance current transformer measures the large current of the alternating current, it needs to be converted into a relatively uniform current in order to facilitate the measurement of the secondary instrument (the secondary rating of the current rated current transformer is 5A or 1A in China), and the voltage on the line. Both are as high as direct measurements are very dangerous. The current transformer acts as a current transformer and electrical isolation. It is a sensor for obtaining electrical primary loop current information in secondary equipment such as measuring instrument and relay protection in power system. The current transformer converts high current into low current proportionally. The current transformer is connected to the primary system at one time, and the secondary side Connect measuring instruments, relay protection, etc.

The core balance current transformer is in an approximate short-circuit state on the secondary side of the transformer during normal operation, and the output voltage is very low. In operation, if the secondary winding is open or the primary winding flows abnormal current (such as lightning current, resonant overcurrent, capacitor charging current, inductor starting current, etc.), it will generate several thousand volts or even tens of thousands of volts over the secondary side. . This not only causes damage to the insulation of the secondary system, but also causes the transformer to be over-excited and burned, even endangering the life safety of the operating personnel.

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