Wiring principle of Power Current Transformer

(1) No open circuit is allowed on the secondary side of the Power Current Transformer. The secondary open circuit may produce serious results, one is that the iron core is overheated, and even the transformer is burnt; 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 Power Current Transformer must be grounded at a point. Because the primary side of the high-voltage Power Current Transformer is high-voltage, when the primary and secondary coils are damaged due to insulation damage, high-voltage breakdown will cause high-voltage to enter low-voltage. If the secondary coil is grounded at one point, high-voltage will be introduced into the ground, which can ensure Safety of persons and equipment. However, it should be noted that the secondary circuit of the Power Current Transformer only allows one point grounding, and no grounding is allowed, otherwise it may cause shunting and affect the application.

The secondary coil of the low-voltage Power Current Transformer should not be grounded. Due to the low voltage of the low-voltage transformer, the insulation between the primary and secondary coils is high, and the possibility of the primary and secondary coils breaking down is small. In addition, the ungrounding of the secondary coil will cause the secondary circuit and the instrument to be ungrounded. The insulation 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 Power Current Transformer 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 Power Current Transformer on both sides should be grounded separately.

(3) The upgrade and maintenance levels of Power Current Transformer 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 saturates, limiting 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 windings of the Power Current Transformer cannot be opened, the windings not used by the Power Current Transformer need to be short-circuited. But for Power Current Transformers with multiple taps, the unused taps should be left empty and cannot be shorted. For example, a Power Current Transformer has taps 1S1, 1S2, and 1S3 twice, where 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 use of the tap.

(5) The metering winding of the Power 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 Power Current Transformer, that is, to determine which side of the L1 device of the Power 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 Power Current Transformer.