Problems in using Power Current Transformer

1 Reason for failure

(1) Due to structural and quality defects, the screw is in poor contact with the screw hole of the insert during operation, resulting in an open circuit;

(2) Because the connecting piece of bakelite is too long, the metal sheet of the rotating terminal is not pressed on the connecting piece, but is pressed on the bakelite sleeve by mistake, resulting in an open circuit;

(3) Errors in repair and test work. If you forget to connect the relay's internal contacts, you won't find it during the acceptance process.

(4) The pressure of the terminal joint of the secondary line is not tight, the loop current is very large, and it is found that the open circuit is caused by combustion or oxidation;

(5) The outdoor terminal cabinet and junction box are wet, and the terminal screws and gaskets are too rusted, resulting in an open circuit

2 Troubleshooting

(1) The loop instrument indicates an abnormal drop or zero;

(2) The Power Current Transformer body has uneven noise such as noise and vibration;

(3) The Power Current Transformer body has serious fever, odor, discoloration, smoke, etc.

(4) Power Current Transformer secondary circuit terminals, components and other joints discharge and become lighter;

(5) Malfunction or refusal of relay protection;

3 Troubleshooting

When looking for the secondary open circuit of the Power Current Transformer, we must first distinguish which group of current loops and open circuits the fault belongs to, and whether it affects the protection. Reports are scheduled and unprotected against possible misuse. Minimize secondary load current. If the Power Current Transformer is seriously damaged, the load should be transferred, and the power outage situation should be checked and dealt with (reverse operation should be adopted as much as possible to avoid user power outage). Short the Power Current Transformer a second time at the nearest test terminal as soon as possible, then check to handle the open point. When short-circuiting, a good short-circuit should be used and performed according to the drawing. If sparks are found during the short circuit, the short circuit is valid. The fault point is below the short contact point of the circuit and can be found by an improved method. If there is no spark during the short circuit, the short circuit has no effect. A loop where the point of failure may be before the point of the short circuit. Short-circuit points can be moved forward point by point to narrow the range. Within the scope of the fault, check the terminals and components that are prone to failure, and check the parts that come into contact when the circuit fails.

For the detected faults, it can be handled by itself, such as loose terminals and other components, poor contact, etc. It can be processed immediately and then placed under revocation protection. If the fault point of the open circuit is on the terminals of the Power Current Transformer, the equipment of 10kV and above should be powered off.