Wiring principles and rules of Power Current Transformer

(1) No open circuit is allowed on the secondary side of Power 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 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 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 Power 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 Power 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 ungrounded secondary coil will cause the secondary

The insulation ability of the road and the meter is improved, which can also reduce the accidents of the instrument burnt down by lightning. In addition, the differential protection is composed of a differential relay (such as BCH-2, etc.). The Power 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 Power Current Transformer on both sides should be grounded separately.

(3) The measurement level and protection level of Power 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 design of the measurement winding core will ensure 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 Power Current Transformer cannot be opened, the unused windings of the Power Current Transformer need to be short-circuited. But for Power Current Transformer 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 for the second time, 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 and 1S3, otherwise it will affect the measurement accuracy of the tap.

(5) When wiring the metering windings of the Power Current Transformer and the relay protection windings that involve the direction, determine the wiring at two points. One is to look at the installation position of the Power Current Transformer, that is, to determine which side of the L1 of the Power 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 Power Current Transformer.