Regarding the issue of simultaneous shutdown of generators by fast-switching devices in the \"SHT 3209-2020 Standards for the Design of Automatic Devices in Power Supply and Distribution Systems in Petrochemical Enterprises\"

Ah, just as the original poster said, according to Clause 5.1.5 in the specification “SHT 3209-2020 Design Code for Automatic Devices in Power Supply and Distribution Systems of Petrochemical Enterprises”, it is indeed possible to perform coordinated switching actions depending on the circumstances. The fast switching takes less than 0.2 seconds; it ensures the safety of the motor without causing a significant drop in its rotational speed. This is what is referred to as “fast switching”” ； The voltage drop on its busbars and the decrease in motor speed are both very small; moreover, the motor’s self-starting current is also not large. If both busbars can withstand the safe operation of their large synchronous generators or synchronous motors, it is acceptable to consider not implementing interconnection switching. Synchronous switching: The switching time is approximately 0.6 seconds. It involves real-time tracking of changes in frequency difference and phase angle difference of the residual voltage, thereby enabling switching between different bus sections. In particular, it captures the first point at which the feedback voltage and the standby power supply voltage are in phase, allowing for closing of the circuit. This process is also known as “synchronous capture switching”. During a simultaneous capture switchover, the bus voltage is typically 65%–75% of the rated voltage; thus, the speed of small motors does not drop significantly, and they can generally still start up smoothly on their own. Given its long switching time, the significant impact it has on the busbars, and the fact that the low-voltage trip time for large synchronous generators is typically around 0.5 to 0.75 seconds with a trip value generally not lower than 80%, it is necessary to carry out simultaneous tripping.