High-Speed Operators Provide Transition in Less Than 100 Milliseconds | B:
To provide the rapid transition necessary to achieve the absolute minimum time in which both Source 1 and Source 2 are simultaneously connected to the load, Russelectric uses special high-speed operators. Transfer occurs only when both sources are within an acceptable window of synchronization. Tests show that transition times are substantially less than 100 milliseconds.
Open-Transition Transfer, Closed-Transition Retransfer and Testing
1| Transfer upon loss of Source 1
Upon reduction of Source 1 voltage below a preset value after a preset time delay, the RTS-03 closed transition switch signals the engine generator (Source 2) to start. When the engine generator has reached acceptable voltage and frequency, the transfer switch transfers to the engine generator source in open transition. The load is served by the engine generator until the ATS detects return of Source 1 to acceptable values. After a preset time delay to allow stabilization of Source 1, the ATS is ready to retransfer.
2| Retransfer upon return of power to the preferred source
When the RTS-03 closed transition switch is ready to retransfer, a synch-check function initiates transfer once the engine generator is in synchronism with Source 1. After the open contacts (Source 1) have closed, the closed contacts (Source 2) open, providing closed-transition transfer.
The period of time in which both sets of contacts are closed is less than 100 milliseconds. A separate timer monitors the closed-transition period, and initiates a signal to reopen the set of contacts that have just been closed, should the closed-transition time exceed the setting of the timer. In addition, a safety signal is provided for customer-connected alarm or remote breaker tripping should the closed-transition period exceed the timer’s setting. Should Source 2 power fail at any time after Source 1 has returned, but before the stabilization time delay relay has timed out, the ATS will automatically open-transition retransfer to Source 1.
3| Load test
Upon initiation of load test, the ATS signals the engine generator (Source 2) to start. When the engine generator has reached acceptable voltage and frequency, a synch-check function initiates transfer to the engine generator in closed transition by closing the Source 2 contacts and then opening the utility (Source 1) contacts. The closed-transition time is less than 100 milliseconds. After the load test period, retransfer to Source 1 is also closed-transition as previously described. The timer monitoring excessive closed transition transfer time is active during this operation. Failure of the generator source during load test will result in automatic open-transition retransfer to the utility source.