Causes of secondary open circuit of current transformer(1) When the secondary line terminal connector is not crimped tightly and the current in the circuit is large, it will be heated, burned out or oxidized, resulting in an open circuit.(2) The outdoor terminal box and junction box are damp, and the terminal bolts and gaskets are excessively rusted, resulting in an open circuit.
(3) Due to the defects in structure and quality, the test wiring terminal in AC current circuit has poor contact between screw and copper plate screw hole during operation, resulting in open circuit.(4) For the test terminal pressing plate in the current circuit, because the glue wood is too long, the metal sheet of the rotating terminal is not pressed on the metal sheet of the pressing plate, but is wrongly pressed on the glue Wood sleeve, resulting in an open circuit.(5) Errors made by the maintenance and test personnel in their work, such as forgetting to connect the internal connector of the relay, could not be found during acceptance.
Treatment of current transformer after secondary open circuit(1) Try to short-circuit the current transformer for the second time on the nearest test terminal, and then check and deal with the open circuit point. During the short-circuit, the special short-circuit wiring for short-circuit shall be used. The short-circuit shall be proper and reliable. It is forbidden to use fuse or general conductor winding, and it shall be carried out according to the drawing.(2) Pay attention to the phenomenon of short-circuit. If there is spark during short-circuit, the short-circuit is effective. The fault point is in the circuit below the short-circuit contact, which can be further found. If there is no spark during short-circuit, the short-circuit may be invalid. The fault point may be in the circuit before the short contact. The short contact can be changed forward point by point to narrow the range.
(3) When shorting the secondary circuit, the staff must adhere to the operation monitoring system, one person operates and one person monitors. Keep an appropriate safe distance from live equipment. Operators must wear insulating boots, insulating gloves and tools with insulating handles. It is forbidden to carry out any work on the circuit between the current transformer and the short-circuit point.
(4) Within the fault range, check the terminals and components prone to failure, and check the parts of the circuit that have been touched during operation. For the faults detected, those that can be handled by themselves can be handled immediately, and then the exited protection can be put into operation. If the open circuit point is on the wiring terminal of the transformer body, the power shall be cut off for treatment. In case of failure that cannot be handled or found out by yourself, report to the superior and send someone to check and deal with it. At this time, the current transformer shall be short circuited for the second time, or the load shall be transferred and the power shall be cut off.
(5) If the secondary open circuit of current transformer is found, it is necessary to distinguish which group of current circuit the fault belongs to, the phase of the open circuit and whether it has an impact on the protection, report to the dispatcher and remove the possible misoperation protection.
Add: Fl 6, No.C12 Building, Lane 299 Guanghua Rd, Ningbo R&D Park,Ningbo Hi-Tech Zone,China, 315040