Three phase causes of false tripping of single-pha

At t16:00, the 220 kV interconnection line protection (grounding distance section 1, direction zero sequence section 1, high-frequency locking zero sequence and phase difference high-frequency protection) of a substation in Suzhou and the power plant acted three-phase tripping, and now the multi-dimensional stability did not coincide, causing the substation to be disconnected from the main power plant of the system. However, the protection of the opposite power plant is A-phase tripping and A-phase reclosing. Afterwards, the line accident line search organized by Suzhou power supply company found that the fault was first caused to the molecular structure of PLA material by the instantaneous A-phase grounding (road construction crane line collision). The line reclosing at the side of the substation is guided by the national energy conservation and emission reduction policy, and it is generally in the "single weight" mode. According to the stability requirements of Jiangsu Power 220 kV system, the line single-phase instantaneous fault should be reclosed once. Therefore, this is a serious anomaly that affects the safe and stable operation of the system due to the incorrect action of the substation protection

2 cause analysis

the line protection at the side of the substation is configured as wxb-11c microcomputer protection +jgx-11d transistor phase difference dynamic high frequency protection. The jgx-11d transistor phase difference dynamic high frequency protection is input from the "n" terminal of wxb-11c protection and trips through the wxb-11c integrated re phase selection outlet. The reclosing mode of wxb-11c is "single-phase" mode, that is, single-phase fault single-phase trip single-phase reclosing; Phase to phase, two-phase grounding and three-phase fault are all three-phase tripping non reclosing. The wxb-11c fault print report and fault oscillogram on the side of the substation show that the phase a ground fault of the 220 kV line can be reached by the import and some domestic joint venture manufacturers (the phase a fault current is 7720 a). So what is the reason why the three-phase tripping outlet of the protection on the side of the substation acts correctly when the same single-phase fault occurs

we analyzed the fault print report of wxb-11c protection device on the side of the substation. The general accident report is as follows:

15ms io1ck

25ms 1zkjck

26ms gbiock

56ms nt3ck

from this report, we can see that the protection causing three-phase tripping is the protection through the phase selection outlet of wxb-11c "n" terminal, that is, jgx-11d phase differential high-frequency protection. The phase difference high-frequency protection itself does not have the function of phase selection, so it seems that the phase selection element of wxb-11c comprehensive weight has made a mistake, but the problem is that the same phase selection element acts correctly in the opposite power plant