Common fault analysis and maintenance methods of current transformer

As an important device in the system, current plays a role in measurement and protection. Once a fault occurs, it is very easy for the power system to fail to operate normally and the power supply function to lose its function. If these faults cannot be eliminated in time, the long-term power outage will have a great impact on people’s daily life and work, and will also have a certain impact on the safety of the power grid. Current transformers are used in various industries and fields. Once a fault occurs, it will cause serious losses. The most likely fault in the current sensor is the current transformer short circuit.

1. Analysis of common faults of current transformers:

Overheating. If the current transformer overheats, smokes, or has glue flow, the reasons may be poor contact of the primary wiring, severe oxidation of the secondary wiring board surface, short circuit between turns in the current transformer, or insulation breakdown of the primary and secondary sides.

Open circuit on the secondary side. At this time, the ammeter suddenly has no indication, the sound of the current transformer increases significantly, and ozone can be smelled and a slight discharge sound can be heard near the open circuit. The hazards of an open circuit on the secondary side are: a. It generates very high voltage, posing a threat to the safety of equipment and operators. b. The core loss increases, and severe heat generation may burn out the equipment. c. The core produces magnetic saturation, which increases the error of the current transformer.

   There is a discharge sound or discharge phenomenon inside. If there is a discharge phenomenon on the surface of the current transformer, it may be that the surface of the transformer is too dirty, causing the insulation to decrease. The internal discharge sound is caused by the reduction of the internal insulation of the current transformer, causing the primary winding to discharge to the secondary winding and the iron core.

Abnormal internal sound. The reasons are: the current transformer core fastening screws are loose, the core is loose, the silicon steel sheet vibration increases, and an abnormal sound that does not change with the primary load is emitted; some cores have a certain buzzing sound when no load or load is stopped due to poor silicon steel sheet assembly process; when the secondary side is open circuit, due to magnetic saturation and non-sinusoidal magnetic flux, the silicon steel sheet vibrates and the vibration is uneven, emitting a large noise; the current transformer is seriously overloaded, which increases the vibration sound of the core.

Serious oil leakage of oil-filled current transformer. If any of the above phenomena is found in the operation of the current transformer, the load should be transferred and the power should be cut off immediately.

 

2. Current transformer fault maintenance and treatment methods:

To effectively solve the problems existing in the transformer, the first thing to change is the environment in which it is located. It cannot be placed in a humid environment. Then replace the transformer. The transformer must be selected to match the load. At the same time, any wrong connections on the line must also be corrected.

When troubleshooting, it is necessary to cut off the power supply system in advance, check its lines, and eliminate the faults in each line little by little. When checking circuit faults, it is necessary to pay attention to safety issues. The voltage of the primary load current must be reduced to a minimum so that the voltage in the secondary circuit can also be reduced. When troubleshooting, the staff needs to wear insulating gloves and tools with good insulation, and also need to operate on insulating pads. When correcting the line, it is also necessary to compare the line drawings with the construction so that the location of each route can be accurately found. Since the secondary open circuit in the current transformer is very hidden and not easy to detect, there is no obvious sign of the transformer during the inspection, but it will always be in an open circuit state. Therefore, when testing it, it is necessary to watch and listen very carefully, and various small details cannot be easily let go.

If heat occurs at the crimping point of the wiring, some abnormal conditions will occur during operation. The correct way to deal with it should be to polish it first to increase its contact area so that it can maintain a good contact state, and then use conductive paste and springs to tighten it so that it can melt and shrink. For manufacturers, the length of the terminal block needs to be appropriately increased, and screws can be used to stabilize it, so that its contact surface can be larger and firmer, reducing the occurrence of heating failures.

 

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