Why should we use the closing bus in electrical engineering ?
The electromagnetic operating mechanism completely relies on the electromagnetic attraction force generated by the closing current flowing through the closing coil to close the trip spring while compressing the trip spring. The trip spring mainly relies on the trip spring to provide energy, so the tripping current of this type of operating mechanism is small, but the closing current Very large, can reach more than 100 amps in an instant, which is why the DC system of the substation needs to open and close the bus control bus. The closing mother provides closing power, and the controller supplies power to the control circuit. The closing bus is directly connected to the battery pack. The closing voltage is the voltage of the battery pack (usually about 240V). When closing, the battery discharge effect is used to provide a large current instantly. At the same time, the voltage drops sharply when closing. The control bus is connected with the closing bus through the silicon chain voltage reduction (generally controlled at 220V), which will not affect the stability of the control bus voltage when closing.
Because the closing current of the electromagnetic operating mechanism is very large, the protection closing circuit is not directly connected to the closing coil, but to the closing contactor. The trip circuit directly connects the trip coil. Closing contactor coils are generally voltage-type and have large resistance values (generally several K). When the protection cooperates with this kind of circuit, it should be noted that the closing and keeping can not be started normally. But this is not a big problem. The trip keep TBJ can generally start, so the anti-jump function still exists. This type of mechanism has a long closing time (120ms ~ 200ms) and a short closing time (60 ~ 80ms).