A new method for overcurrent protection of cascaded radial distribution lines

Abstract

The invention belongs to the technical field of relay protection of electrical power systems and relates to a novel method for performing over-current protection on cascade radiation type distribution lines. The method is implemented through IPUs (intelligent protection units), optical fiber communication networks and master stations, each IPU is installed at the outlet of each line, meanwhile, point-to-point fast communication between the superior and subordinate IPUs can be realized on the basis of the optical fiber networks, the superior and subordinate relationship between the IPUs can be obtained through the master stations, the subordinate IPUs can transmit protection information to the superior IPUs timely, each grade of IPU is provided with main protection and backup protection, and setting of action currents of the main protection and the backup protection is set as per a principle of avoiding of the maximum load current. According to the method, the selectivity is guaranteed through over-current locking signals or an action time limit between the superior and subordinate protection, so that the problem of override tripping existing in protection of the cascade distribution lines can be thoroughly solved, the main protection is smaller in constant action value and higher in sensitivity, and meanwhile, both the reliability and the quickness of the protection are considered.

Description

technical field [0001] The invention belongs to the technical field of electric power system relay protection, and in particular relates to a method for overcurrent protection of cascaded radial distribution lines. Background technique [0002] "Closed-loop design, open-loop operation" is the basic principle of power distribution system design. At present, most distribution lines adopt open-loop (that is, radiation type) operation mode, and the three-stage current protection is a radiation type distribution line. basic form of protection. In order to ensure selectivity, in the traditional three-stage current protection, the protection stage I is set according to the current when a three-phase short circuit occurs at the end of the line in the maximum operation mode, and the protection stage II is set according to the action of the lower line I stage. The value is set, and the selectivity is guaranteed by setting the time limit; the section III of the protection is set based...

AI Technical Summary

Problems solved by technology

In a general cascaded line, especially when the distance between each section is long, the upper and lower protections can cooperate well; but when the line is short, the cooperation between the protections is difficult, which may easily lead to the problem of over-level tripping, and it is difficult to ensure selectivity

Since the action current and action time limit settings of sections I, II, and III of each level of line protection are different, they need to be calculated and checked one by one, and the setting calculation is cumbersome. Moreover, when the topology of the system changes, the protection performance is difficult to guarantee.

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