Current differential protection is a kind of protection in relay protection. The positive phase sequence is 120 degrees before B and C before B-ultrasound. Reverse order (that is, reverse order) means that A leads C, and C leads B by 120 degrees respectively. The reverse of active power is only the included angle between voltage and current plus 180 degrees, which is reverse power, not reverse phase sequence.
Extended data
Principle of differential protection:
The differential protection works by using Kirchhoff current theorem. When the transformer works normally or fails outside the area, it is regarded as an ideal transformer, then the current flowing into the transformer is equal to the current flowing out (converted current), and the differential relay does not act.
When there is an internal fault in the transformer, two sides (or three sides) provide short-circuit current to the fault point, and the sum of the secondary currents felt by the differential protection is proportional to the current at the fault point, so that the differential relay operates.
The principle of differential protection is simple, the power consumption is low, the protection range is clear, and the action does not need delay, so it has always been used as the main protection of transformer. In addition, differential protection also includes line differential protection and bus differential protection.
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