It has been analyzed that when the storage time of the switch spring exceeds the recharge time of the recloser, and the test is terminated due to a permanent fault, the recloser will close the circuit breaker after a delay. At this point, the operating mechanism begins to re-store energy. The energy storage time is longer than 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, causing the TWJ (Trip Wire Junction) to remain inactive. The protection system then assumes the circuit breaker is in the closed position. After 15 seconds, the battery charges, and once the energy storage is complete, the closing circuit is reconnected via the energy storage latching contact, which excites the TWJ. At this moment, the protection system detects that the circuit breaker has tripped and initiates the reclosing function. This leads to repeated reclosing on a permanent fault, increasing the risk of an accident.
This situation may not be immediately noticeable 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 cause the storage time to become excessively long. Additionally, when the DC voltage drops, the energy storage motor may not provide sufficient power. In both scenarios, the circuit breaker may repeatedly reclose after a permanent fault has occurred, leading to potential damage or further issues.
When the operating mechanism is not storing energy, it is not ready for operation. Attempting to charge the recloser at this point is ineffective and could lead to errors. One solution is to learn from the pressure reduction blocking method used in hydraulic operating mechanisms. When the mechanism is not storing energy, the un-storage contact can be used to activate a pressure reduction relay within the operating box, thereby locking out the recloser until energy is properly stored. For example, the storage tank switch contact (SP1) can trigger the 2YJJ relay in the operating box, and the 2YJJ contact can be used to lock out the protection's reclosing function.
Another issue occurs when a local opening of the circuit breaker causes a reclosing action. For instance, if the circuit breaker is opened locally, the protection system might incorrectly interpret this as a trip, triggering a reclosing attempt. During local operations, if the protection does not receive the signal, the control circuit remains active (due to SM1 being shorted), and the protection device mistakenly believes the circuit breaker has tripped. When the protection reclosing is triggered, the circuit breaker will automatically close again once power is restored.
To address this, Measure 1 involves transferring the local operation circuit and using manual relays such as the SHJ (Manual Closing Relay) and STJ (Manual Tripping Relay) on the protection panel to perform opening and closing operations. This approach effectively prevents reclosing failures. Measure 2 involves identifying a pair of contacts on the remote/local switch (SM3). When switching to local control, these contacts close and send a signal to the operating box, activating the pressure reduction latching recloser relay (2YJJ). This sends a central signal, helping to prevent operators or maintenance personnel from forgetting to switch back to remote control, thus blocking the recloser. This method is illustrated in Figure 2 and can also share a common loop with the 2YJJ relay, improving efficiency and reliability.
Additionally, when the circuit breaker closes, the arc-cutting capacitor can generate an accidental sound signal. This happens when the circuit breaker closes and the accident sound is triggered at the end of the operating mechanism’s energy storage. Normally, the accident sound is activated through the series connection of the TWJ normally open contact and the KK1-3, KK17-19 contacts. When the circuit breaker is closed using the KK switch, these contacts are connected, and the operating mechanism starts to store energy. At this point, the energy storage contact SP1 and the circuit breaker auxiliary contact SP2 open, causing the TWJ to de-energize. There is 110V on both C2 and C3 in the capacitor control signal circuit. Once the energy storage ends, SP1 closes and shorts C3. Since the voltage on C2 cannot change abruptly, the voltage across the TWJ rises to 110V, and as C2 charges up to 220V, the TWJ voltage drops to 0V. This process causes the TWJ to act momentarily, resulting in an instantaneous accident sound signal.
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