The current transformer is based on the electromagnetic induction principle to measure the instrument of the secondary side small current to measurement. The current transformer is composed of closed cores and windings. Its a number of turns is rare, and string in the line that needs to be measured.
First, current transformer operation maintenance
During the operation of the current transformer, the operator should regularly maintain the inspection, usually in the test, ear listening, and the nasal sniffing method, and the specific inspection content has the following:
1, visual inspection
A. Whether the terminal is overheated, discolored. The first loop wiring should be firm, and the joints are not loose.
b, the oil level is normal, whether it is discolored, and the oil level meter leaks oil.
C, is cleaned, there is cracking and shower traces
D. Check if the secondary side is firm, the wiring of the instrument on the secondary side is tight, check whether the secondary terminal is good, there is no open circuit discharge or fire.
E, check if the terminal box is cleaned, there is no debris
2, ear listening
A. Is there an abnormal sound?
b, the current transformer has no bigger buzz due to fixation
C, there is no abnormal sound due to the secondary opening
3, nose sniffing
A. Check if the ambiguity generated due to overload
B. Check if there is an ozone flavor that causes discharge generation due to poor contact poor contact.
Characteristics, use, and maintenance of current transformer operation
Second, the characteristics of current transformers
Current transformers typically have two forms of electromagnetic and capacitive formation. Its one winding is directly serially connected in power lines, and the number of turns is small. The current in the one winding is completely dependent on the current of the line; the turn of the secondary winding There are more, in series in the measuring instrument or relay protection loop. When the current transformer is working, its secondary loop is always closed, but the working conditions of the measuring instrument and relay protection device are small, and the working conditions of the current transformer are short-circuited, and its current is The impedance of the secondary loop is independent.
The secondary side rated current of the current transformer is generally 5A or 1A. The secondary circuit of the current transformer is not allowed to open, because the secondary side opening will generate a high voltage, directly affect the security of the equipment and operators. In order to ensure the safety of the staff in contact with the measuring instrument, the secondary side of the current transformer must be reliably grounded, and the secondary circuit of the current transformer should be opened before the secondary circuit of the current transformer should be shorted. .
Third, the use of current transformers
The current transformer is one of the main electrical equipment of the substation. It mainly provides protection, the secondary current for measurement, and the primary side is connected to the secondary high voltage device, and the secondary side is connected to the secondary device. It not only makes measuring instruments and relay protection The secondary electrical equipment is effectively isolated from the high-voltage electrical device to ensure the safety of the staff, and the measuring instrument and relay can be standardized and miniaturized, and the electric wire, the cable is long, and the cable is measured; when the high voltage side occurs When there is a disconnection, the current transformer can protect the current coil of the measuring instrument is not damaged by the large current.