Did You Know That There Is So Much Knowledge About Circuit Breaker Protection? (two)

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About automatic reclosing
1. Requirements for automatic reclosing sequence
In Figure 1, if a short circuit occurs in line 2, the protection action of line 2 will trip circuit breakers 5021 and 5022, and reclosing will naturally close these two circuit breakers. Considering the possibility of overlapping on the permanent fault line, in order to reduce the impact, the two circuit breakers should not be overlapping at the same time. So there is a sequence problem of which one should be overlapped first.
Should the side circuit breaker or the middle circuit breaker be closed first?
If the intermediate circuit breaker 5022 is closed first, and it coincides with the permanent fault, the line protection will then trip the 5022 circuit breaker. In case the 5022 circuit breaker fails at this time, the failure protection of the 5022 intermediate circuit breaker will trip the 5023 circuit breaker, and concurrently trip the circuit breakers on each side of the No. 2 main transformer (if the circuit breaker is connected, the circuit breaker on the opposite side will be tripped), which will It affects the operation of the No. 2 main transformer (or line) of the connecting component, so the intermediate circuit breaker cannot be reclosed first.
If the side circuit breaker 5021 is closed first and it also coincides with the permanent fault, the line protection will then trip the 5021 circuit breaker. In case the 5021 circuit breaker fails at this time, the 5021 circuit breaker failure protection will trip all side circuit breakers on bus I, and send a far jump to trip the circuit breaker on the opposite side of line 2. The work of the connecting components or other components of line 2 will not be affected. .
Therefore, when the line protection trips two circuit breakers, the side circuit breaker should be closed first, and then the circuit breaker should be closed after the side circuit breaker is successfully reclosed. At this time, the circuit breaker must be closed to the intact line. If the side circuit breaker fails to reclose and closes on the faulty line, the protection will trip the side circuit breaker again, and at this time the circuit breaker will no longer reclose.

2. Reclosing startup and mode adjustment
Reclosing can be started in two ways: position non-corresponding start and external trip start. External tripping initiation refers to the line protection action issuing a tripping command and initiating reclosing at the same time.
o Starts that do not correspond to the position are divided into: single-phase stolen jump start and three-phase stolen jump start.
o Protection trip start is divided into: single-phase trip start and three-phase trip start.
Regarding the setting method of reclosing, you can choose one of four methods according to your needs: single-phase reclosing, three-phase reclosing, comprehensive reclosing and reclosing deactivation. The reclosing mode can be selected using either the switch on the screen or the control word in the setting sheet.

3. Reclosing inspection method
Reclosing inspection method: When the three-phase line trip requires three-phase reclosing, the following three methods can be used.
§? Check the synchronization method: the line and synchronization voltages are both greater than 40V, and then the phase difference between the line voltage and the same phase voltage in the synchronization voltage is within the fixed value setting range.
§ No-voltage detection method: Check that the line or synchronization voltage is less than 30V, and the corresponding TV is not disconnected.
§ No verification method: No inspection is performed, and a closing command is issued when the time is up.