System Sequence Of Operation

摘要

The following is an example of a sequence of operation for a typical emergency power system.rn1. Normal utility power supply source fails.rn2. The automatic transfer switch (ATS) or normal power supply switchgear relay (loss of voltage/frequency sensing) sends a start signal to the generator control system.rn3. Generators start and parallel to bus. Normal operating voltage and frequency are achieved.rn4. ATS senses the availability of an alternate power source or receives a permissive transfer signal from the emergency generator control system to transfer to the alternate source side. Emergency loads are picked up sequentially by the emergency generator's bus in accordance with load priority setting.rn5. The generator control system optimizes the control of the generators, shutting off and starting generators as needed.rn6. The generator control system also should have the capability to control load shed operation, sending signals to load breakers and/or ATS devices removing loads from the emergency system in accordance with load priority setting to prevent generator overloading. This requires fast control processing as well as direct control of load serving breakers.rn7. Normal utility power supply source returns.rn8. ATS transfers back to normal power supply source. The transfer can be either an open transition (momentary power interruption) or a momentary closed transition (no power interruption), depending on the emergency load requirements and the function and feature of the ATS installed.rn9. Generators cool down and shut down.