It has been analyzed that when the storage time of the switch spring exceeds the reclosing charging time, and the test is terminated due to a permanent fault protection, the recloser will close the circuit breaker after a delay. At this point, the operating mechanism begins re-storing energy. The energy storage time exceeds 15 seconds, but the protection system accelerates the tripping of the circuit breaker. As a result, the closing circuit is disconnected by the stored energy blocking contact, and the TWJ (Trip Coil) is not energized. Consequently, the protection system assumes the circuit breaker is in the closed position. After 15 seconds, the battery is charged. Once the energy storage is complete, the closing circuit is reconnected via the energy storage latching contact, and the TWJ becomes energized. At this moment, the protection system interprets the circuit breaker as being in the tripped state, leading to another reclosing action. This can cause the circuit breaker to repeatedly close on a permanent fault, increasing the severity of the incident.
This issue may not be evident when the spring energy storage time is shorter than the reclosing charging time, but it still represents a hidden risk. Typically, the measured energy storage time for a spring mechanism is around 12 seconds. However, during the replacement of a batch of circuit breakers, failures in the energy storage motor can lead to excessively long storage times. Additionally, if the DC voltage drops, the energy storage motor may not provide sufficient power. In both scenarios, the circuit breaker may be re-closed multiple times after a permanent fault occurs.
When the operating mechanism is not storing energy, it is not ready to operate. Therefore, the reclosing charge is ineffective and potentially misleading. We can take inspiration from hydraulic operating mechanisms, which use pressure reduction blocking methods. When the operating mechanism is not storing energy, the un-storage contact can activate a pressure reduction blocking relay within the operating box, effectively locking out the reclosing function. For example, the storage tank switch contact (SP1) can trigger the 2YJJ relay in the operating box, and the 2YJJ contact can then be used to lock out the protection system’s reclosing function.
Another phenomenon involves the reclosing action triggered by a local opening of the circuit breaker. For instance, if the circuit breaker is opened locally, the protection system may still initiate a reclosing operation. During local operation analysis, since the protection signal is not transmitted, the control circuit cannot be cut off (as SM1 contact is already shorted). Therefore, the protection device mistakenly assumes the circuit breaker has tripped. When the protection system completes its reclosing charge, it will attempt to close the circuit breaker again once power is restored.
To address this, Measure 1 involves transferring the local operation circuit and performing opening and closing operations through the manual relay (SHJ) and manual trip relay (STJ) on the protection screen. This helps prevent reclosing failures. Measure 2 involves using a pair of contacts on the remote/local switch (SM3). When switching to local control, the contacts close and send a signal to the operating box, activating the pressure reduction latching recloser relay (2YJJ). This sends a central signal to alert operators and maintenance personnel, ensuring they do not forget to switch back to remote control. The author implemented this method, as shown in Figure 2, and it also shares a 270V loop with the energy storage lockout start and pressure reduction latching recloser relay (2YJJ).
When the circuit breaker closes, the arc-cutting capacitor may produce an accidental sound signal. Additionally, an accident sound may occur at the end of the operating mechanism's energy storage. Normally, the accident sound is not activated by the TWJ normally open contact or the KK1-3, KK17-19 contacts in series. However, when the circuit breaker is closed using the KK switch, the KK1-3 and KK17-19 contacts are connected. As the operating mechanism stores energy, the SP1 and SP2 auxiliary contacts open, causing the TWJ to de-energize. At this point, there is 110V on both C2 and C3. When the energy storage ends, SP1 closes, shorting C3. Since the voltage on C2 cannot change abruptly, the voltage on the TWJ rises to 110V. As C2 charges to 220V, the TWJ voltage drops to 0V. This process causes the TWJ to briefly act, triggering the accident sound signal immediately.
Diesel Water Pump
Diesel Engine water pump is a common industrial equipment, which is widely used in agriculture, construction, engineering, fire protection and other fields. Its main function is to convert the power generated by the diesel engine into the power of water, so as to realize the delivery and supply of water. This article will introduce the working principle, structural characteristics, application fields and maintenance of diesel engine water pump.
The working principle of the diesel engine water pump is to use the power generated by the combustion capacity of the diesel engine to transmit the power to the water pump through the connecting rod mechanism, so as to drive the water pump to work. The working process of diesel engine water pump can be divided into three stages: water absorption, water pressure and drainage. In the suction stage, the diesel engine generates negative pressure through the up and down movement of the piston to draw water from the water source into the water inlet of the water pump; in the pressurized water stage, the piston of the diesel engine moves upwards to press the water into the pressurized water chamber of the water pump; in the drainage stage, the piston of the diesel engine moves downward to discharge the water from the outlet of the water pump.
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