Phase-sequence synthetic brake method for preventing multi-branch transformer differentical protection malfunction

Abstract

A phase sequence combination braking method for preventing multibranch transformer differential protection misoperation is to make up of ratio brake elements by the maximum value of the zero sequence current of each neutral point earth (or branch) and the positive or the negative sequence currents of the three phase differential current in the transformer differential protection. When the ratio value is smaller than that of the setting K, then it is decided that the earth out of the neutral point earth is fault and a three-phase brake signal is output to brake the three phase ratio differential protection which can prevent transformer differential protection misoperation resulted from the earth fault out of the neutral point earth when errors of three phase current inductors are different.

Description

technical field

[0001] The invention relates to a transformer protection method, in particular to a phase sequence synthesis braking method for preventing misoperation of differential protection of multi-branch transformers. Background technique

[0002] The existing differential protection device for power transformers can identify external faults and internal faults through the ratio braking criterion, that is, the ratio of differential current to ride-through current; By analyzing the waveform or harmonic content of the differential current, the excitation inrush current and the overexcitation current can be identified to achieve the purpose of judging internal faults. For power transformers with two or more neutral points directly grounded, when an out-of-area ground fault occurs on one neutral point grounding side, there may be large ground fault zero-sequence currents on multiple grounding sides. In order to prevent the zero-sequence current from causing the different...

Examples

Embodiment 1

[0011] A phase sequence synthesis braking method for preventing misoperation of differential protection of multi-branch transformers figure 1 A circuit of a positive-sequence synthetic braking device for preventing the misoperation of differential protection of multi-branch transformers is realized. The device consists of filters 01, 02, 03, fundamental positive sequence filter 1, filter 2, and the The value circuit 3, the multiplier 4 and the comparator 5 are constituted, wherein the input terminals of the filters 01, 02 and 03 respectively input the zero-sequence current instantaneous value signal 3i of each neutral point grounding side or branch of the transformer 10 , 3i 20 , 3i 30 , 3i 10 , 3i 20 , 3i 30 After filtering, 3I is obtained 10 , 3I 20 , 3I 30 , the output terminals of the filters 01, 02 and 03 are respectively connected with the input terminal of the maximum value circuit 3, one input terminal of the multiplier 4 is connected to the output terminal of t...

technical field

[0001] The invention relates to a transformer protection method, in particular to a phase sequence synthesis braking method for preventing misoperation of differential protection of multi-branch transformers. Background technique

[0002] The existing differential protection device for power transformers can identify external faults and internal faults through the ratio braking criterion, that is, the ratio of differential current to ride-through current; By analyzing the waveform or harmonic content of the differential current, the excitation inrush current and the overexcitation current can be identified to achieve the purpose of judging internal faults. For power transformers with two or more neutral points directly grounded, when an out-of-area ground fault occurs on one neutral point grounding side, there may be large ground fault zero-sequence currents on multiple grounding sides. In order to prevent the zero-sequence current from causing the different...

Examples

Embodiment 1

[0011] A phase sequence synthesis braking method for preventing misoperation of differential protection of multi-branch transformers figure 1 A circuit of a positive-sequence synthetic braking device for preventing the misoperation of differential protection of multi-branch transformers is realized. The device consists of filters 01, 02, 03, fundamental positive sequence filter 1, filter 2, and the The value circuit 3, the multiplier 4 and the comparator 5 are constituted, wherein the input terminals of the filters 01, 02 and 03 respectively input the zero-sequence current instantaneous value signal 3i of each neutral point grounding side or branch of the transformer 10 , 3i 20 , 3i 30 , 3i 10 , 3i 20 , 3i 30 After filtering, 3I is obtained 10 , 3I 20 , 3I 30 , the output terminals of the filters 01, 02 and 03 are respectively connected with the input terminal of the maximum value circuit 3, one input terminal of the multiplier 4 is connected to the output terminal of t...

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