Wiring principle of Electrical Current Transformer

(1) No open circuit is allowed on the secondary side of Electrical Current Transformer. The secondary open circuit may have serious consequences, 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 dangerous high voltages, endangering the safety of people and equipment.

(2) The secondary side of the high-voltage Electrical Current Transformer must have a point of grounding. Because the primary side of the high-voltage Electrical 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 Personal and equipment safety. However, it should be noted that the secondary circuit of the Electrical Current Transformer only allows one point grounding, and no grounding is allowed, otherwise it may cause shunting and affect the use.

The secondary coil of the low-voltage Electrical Current Transformer should not be grounded. Due to the low voltage of the low-voltage transformer, the degree of insulation between the primary and secondary coils is great, and the possibility of the primary and secondary coil breakdown is small. In addition, the non-grounding of the secondary coil will cause the secondary return

The increase in insulation capacity of roads and meters can also reduce the number of meter burnt accidents caused by lightning. In addition, the differential protection is composed of a differential relay (such as BCH-2, etc.). The Electrical Current Transformer on both sides of the differential protection can only be grounded at one point. Generally, the grounding point is set at the protection screen, and when the differential protection is used When the microcomputer protection device is used, the Electrical Current Transformer on both sides should be grounded separately.

(3) The measurement level and protection level of Electrical Current Transformer cannot be connected wrongly. Due to the different thicknesses of the measurement and protection winding cores, if they are connected incorrectly, the accuracy of the measurement during normal operation will be reduced and the electric energy measurement will be inaccurate; the second is that when a short-circuit fault occurs, the measurement winding core is guaranteed 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 protect the instrument. However, the iron core of the relay protection winding is not saturated, and the secondary current increases correspondingly with the short-circuit current, so that the relay protection operates accurately. If it is connected incorrectly, the relay protection action is not sensitive, and the meter may burn out.

(4) Since the secondary windings of the Electrical Current Transformer cannot be opened, the unused windings of the Electrical Current Transformer need to be short-circuited. However, for an Electrical Current Transformer with multiple taps, the unused taps should be left empty and cannot be shorted. For example, an Electrical Current Transformer has taps 1S1, 1S2, and 1S3 twice, where 1S1, 1S2 are 300/5A, and 1S1, 1S3 are 600 /5A, when you need to use 300/5A, connect 1S1 and 1S2 to use, you should not short-circuit 1S1, 1S3, otherwise it will affect the measurement accuracy of the tap.

(5) When wiring the metering winding of the Electrical Current Transformer and the relay protection winding that involves the direction, determine the wiring at two points. One is to look at the installation position of the Electrical Current Transformer, that is, to determine which side of the L1 of the Electrical Current Transformer is installed; It depends on the winding function or the type of relay protection. The above two points can determine the secondary wiring of the Electrical Current Transformer.