(1) No open circuit is allowed on the secondary side of the current transformer. The secondary open circuit may produce serious results. One is that the iron core is overheated and even the transformer is burned; the other is that the number of turns of the secondary winding is large, which will induce risky high voltages, endangering the safety of people and equipment.
(2) The secondary side of the high voltage current transformer must be grounded at a point. Because the primary side of the high-voltage current transformer is high-voltage, when the high-voltage breakdown between the primary and secondary coils due to insulation damage will cause the high-voltage to enter the low-voltage, if the secondary coil is grounded at one point, the high-voltage will be introduced into the earth to ensure Safety of persons and equipment. But it should be noted that the secondary circuit of the current transformer is only allowed to be grounded at one point, and no grounding is allowed, otherwise it may cause shunting and affect the application.
The secondary coil of the low-voltage current transformer should not be grounded. Due to the low voltage of the low-voltage transformer, the insulation desire between the primary and secondary coils is great, and the possibility of the primary and secondary coils breaking down is small. In addition, the non-grounding of the secondary coil will cause the secondary return
The insulation of the road and the meter can be improved, and it can also reduce the accidents of the instrument burnt down by lightning. In addition, the differential maintenance is composed of a differential relay (such as BCH-2, etc.). The current transformers on both sides of the differential maintenance can only be grounded at one point. Generally, the grounding point is set at the maintenance screen, and when the differential maintenance is used When the computer is maintained and installed, the current transformers on both sides should be grounded separately.
(3) The improved and maintenance levels of current transformers cannot be connected wrongly. Due to the difference in the thickness of the winding core design for the improvement and maintenance, if the wrong connection is made, the accuracy of the improvement during normal operation will be reduced and the electric energy measurement will be inaccurate; When the short-circuit current exceeds a certain multiple of the rated current, the iron core is saturated, which limits the growth of the secondary current to maintain the instrument. However, the iron core of the relay maintenance winding is not saturated, and the secondary current increases correspondingly with the short-circuit current to make the relay maintenance action. If the connection is wrong, the relay maintenance action is not flexible, and the meter may burn out.
(4) Since the secondary winding of the current transformer cannot be opened, the unused windings of the current transformer need to be short-circuited. However, for a current transformer with multiple taps, the unused taps should be empty and cannot be short-circuited. For example, a current transformer has taps 1S1, 1S2, and 1S3 for the second time, of which 1S1, 1S2 are 300/5A, and 1S1, 1S3 are 600 /5A. When 300/5A is required, connect 1S1 and 1S2 to use. 1S1 and 1S3 should not be short-circuited, otherwise it will affect the accuracy of the tap.
(5) The metering winding of the current transformer and the relay maintenance winding connection that involve the direction control two points to confirm the connection, one is to look at the device position of the current transformer, that is, to determine which side of the L1 device of the current transformer is; It depends on the winding function or the type of relay maintenance. The above two points can confirm the secondary wiring of the current transformer.