Operation Precautions of Current Transformers and the Cause of Burning

Ⅰ. What are the precautions for the operation of current transformers?

In the power supply line, the current and voltage vary greatly from a few amperes to tens of thousands of amperes. In order to facilitate the measurement of the secondary instrument, it needs to be converted into a relatively uniform current. In addition, the voltage on the line is relatively high, such as direct measurement, which is very risky. The CT current transformer plays the role of current conversion and electrical isolation. The matters needing attention in the operation of the CT current transformer are:

1. The secondary side of the CT current transformer must not be opened during operation. Once the secondary side is open, it will burn out due to excessive iron loss and high temperature, or the secondary winding voltage will rise and the insulation will be broken down, resulting in the risk of high-voltage electric shock. . Therefore, when exchanging meters, such as exchanging ammeters, active meters, reactive meters, etc., the current loop should be short-circuited first, and then the metering meters should be exchanged.

When the meter is adjusted, first connect it to the secondary circuit, then remove the short-circuit and check whether the meter is normal. If sparks are found when the short-circuit is removed, the current transformer has been opened at this time, and the short-circuit should be re-shorted immediately, and the short-circuit can be removed only when it is confirmed that there is no open-circuit in the circuit of the meter. When stopping the work of removing the short circuit of the current transformer, you should stand on the insulating pad. In addition, you should consider the maintenance and installation of the current transformer circuit. After the work is completed, the maintenance and installation can be put into operation.

2. When the insulation resistance of the secondary coil of the current transformer is lower than 10~20 megohms, the drying treatment must be stopped to restore the insulation before use.

3. One end of the secondary side of the current transformer and the outer casing should be firmly grounded.

4. If the current transformer has a humming sound, check whether the internal dead center is loose, and the dead center bolt can be tightened.

Ⅱ. What are the reasons for the current transformers to burn out?

There are many reasons for the burnout of the current transformers. As long as the basic cause is found, the target can be clearly defined and countermeasures can be taken in time.

1. Install circuit breakers to prevent branch failures involving the entire line from power outages, especially to ensure that branch circuit breakers can trip reliably.

2. Connect the current transformer to the back of the circuit breaker to ensure that the circuit breaker and arrester operate correctly when the transformer fails to remove the fault.

3. Strengthen the high-voltage insulation experiment of the user's current transformers and arresters, find out the insulation aging level of the transformers and arresters as soon as possible, and replace them in time to prevent the transformers from burning out and causing power outages.

4. In addition, it is necessary to regularly clean the user's primary equipment to reduce pollution and prevent the insulation from being lowered.

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