1. Items to be checked when the current transformer is regularly inspected. How to correctly judge whether there is a fault and how to deal with it. What are the common faults of current transformers?
Common faults of current transformers are:
1. The secondary side of the current transformer is open circuit
2. The temperature of the current transformer is too high during operation
3. There is smoke or odor inside the current transformer when it is running
4. The previous screw of the current transformer is loose. Short circuit between turns or layers
5. The internal charge and discharge of the current transformer. The sound is abnormal or the electric spark is formed between the wire and the shell
6. The oil-filled current transformer has serious oil leakage or the oil level is too low
B. Usually, the fault is judged and handled according to the actual abnormal situation. If you use the temperature test wax piece to check the temperature, judge the open circuit according to the sound from the device and the indication value of the needle.
Generally, it should be judged and solved according to the abnormal situation that occurred. For example, use a test wax piece to check the hot condition. According to the sound and the meter mark to distinguish whether it is leading the way. Once you see a common fault, you should immediately repair or replace it. The normal inspection items are as follows:
1. Check for over-temperature problems and abnormal odors
2. Check the condition of the insulation layer on time
3. Check whether the three-phase indication value of the ammeter is within the allowable standard. Whether it is operating under load
4. Whether the porcelain part is cleaned in detail and complete, whether there is damage or discharge condition
5. Whether the oil quantity of the oil-type current transformer is in the normal range, and whether there is oil leakage
2. Why is the secondary side of the current transformer not allowed to open circuit? What are the risks after the open circuit?
1. Generally, the magnitude of the primary current of the current transformer is irrelevant to the magnitude of the current of the secondary load.
When the current transformer is in normal operation. Because the impedance of the secondary side is not large (close to the short-circuit fault condition). Most of the magnetic lines of force caused by the primary current are compensated by the secondary current, and the total magnetic flux density is not large. Potential is not high. But when the secondary open circuit. The secondary current is equal to zero, the primary current completely becomes the excitation current, which will generate a high potential in the secondary coil (the peak value can reach several thousand volts, or even higher), which will not only damage Secondary insulation, but also a threat to personal safety. In addition, the excessive expansion of the magnetic flux density of the iron core may also cause the iron core to be damaged due to overheating.
3. Long-term overload damage of current transformers
Once the current transformer is overloaded for a long time, the magnetic flux density of the iron core will be saturated, and the deviation of the current transformer will be enlarged, and the meter is marked incorrectly, so it is not easy to grasp the specific load or operation status. In addition, due to the expansion of the magnetic flux density, the iron core and the secondary electromagnetic coil will be overheated, and the insulating layer will be destroyed.
4. Omens and solutions of the open circuit on the secondary side of the current transformer:
When the secondary side of the current transformer is open, it is often accompanied by the following conditions:
1. The ammeter and the power factor meter are marked as zero, the meter does not turn, and there is a buzzing sound.
2. The current transformer itself has creaking discharge sound or other abnormal sound, and the terminal block is likely to be burnt.
When the current transformer is open, the resulting potential difference is somewhat related to the magnitude of the primary current. Therefore, when solving the common fault of the open circuit of the current transformer, it is necessary to reduce the load or make the load zero, and then use the special tools for the insulation layer to solve the problem, and stop using the corresponding protection equipment when solving the problem.
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