1. Insulation fault
An insulation problem is one of the common faults of a current transformer. Long-term operation in a high-voltage and high-humidity environment makes the insulation material of the transformer prone to aging and moisture, resulting in reduced insulation performance. When the insulation resistance is reduced to a certain extent, it may cause a short circuit between windings or between windings and iron cores and shells. For example, in a humid outdoor substation, if rainwater penetrates into the interior of the current transformer and corrodes the insulation layer, the insulation performance will gradually deteriorate and may eventually lead to insulation breakdown, causing serious power accidents.
2. Winding fault
Winding faults include winding short circuits and open circuits. Due to the long-term passage of large current, the winding wire may burn out due to overheating, resulting in an open circuit. In addition, after the winding insulation is damaged, a short circuit may occur between adjacent wires. A short circuit will change the transformation ratio of the current transformer, affect the measurement accuracy, and may also cause heating, smoking, and even fire. Near some electrical equipment that is frequently started and has a large current impact, the winding of the current transformer is more likely to fail due to excessive current impact.
3. Core failure
Core failure is mainly manifested as core overheating and decreased core magnetic permeability. When there are multiple grounding points in the core, a circulating current will be formed, causing the core to overheat. Long-term overheating will cause the insulating paint of the core to age and fall off, further aggravating the damage to the core and affecting the performance of the transformer. In addition, if the core is hit by an external force, vibrated, or is in a strong magnetic field interference environment for a long time, its magnetic permeability may decrease, resulting in a decrease in the electromagnetic conversion efficiency of the transformer, an increase in the ratio error and phase error, and an inability to accurately measure the current.
4. Secondary circuit failure
Poor connection in the secondary circuit is a common problem. For example, loose terminals and increased contact resistance will lead to poor secondary current transmission, abnormal indication of the measuring instrument, and the relay protection device may malfunction or refuse to operate. An open circuit in the secondary circuit is also a serious fault. Once the circuit is open, the secondary winding will induce a high voltage, endangering the safety of equipment and personnel. After the secondary circuit is inspected and maintained, if the wiring is not restored correctly, an open circuit fault is likely to occur.
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