Abstract: The invention relates to a method of differential protection in the power distribution networks based on phase difference principles. The method comprises the following steps: collecting the current and voltage signals of each loading switch; calculating phase difference between the corresponding currents at two adjacent loading switches, wherein at least one of the two adjacent loading switches accords with ?I? max>n·?IT+?Idz; tripping the two adjacent loading switches if the phase difference corresponding to the two adjacent loading switches being greater than a threshold then a section between the two adjacent loading switches being determined as a fault section. The method only needs to calculate the phase difference between the corresponding currents at the two adjacent loading switches, and achieves the fault determination according to the phase difference being greater than the threshold.

Abstract: The present invention relates to a method of preventing misoperation about a relay protection device in a smart substation. Reversely operating CPU operation results of two operation records about the relay protection device, in order to form corresponding disassembler codes. According to disassembler codes, calculating similarity of the CPU operation results of the two operation records about the relay protection device by a structured method. Judging whether the similarity is greater than a set threshold or not. If the similarity is greater than the set threshold, the CPU operation results of the two operation records about the relay protection device to be the same, otherwise, the CPU operation results of the two operation records about the relay protection device are judged to be different. The present invention avoids the misoperations of the relay protection device on operation.

Abstract: The present invention relates to a differential protection method for bridge circuit in current converter control system, including the steps of: 1). obtaining sample values of the three-phase current for the current converter control system at AC side thereof, and calculating the absolute value of each sampling value respectively; 2). calculating a value of current at the AC side of the current converter control system; and 3). determining whether to perform a relay protection for the current converter control system according to the value current at the AC side of the current converter control system. The method of the present invention provided, is fast, convenient, and with a small amount of calculation. The current converter control system determines whether to perform a relay protection in a short time. Also it reduces the possibility that the equipment burned because of cannot break the circuit in time.