Chapter 3
Power System Phenomena and Their Impact on Relay System Performance
Power system phenomena are normally captured and defined during the analysis of power system disturbances. Power system phenomena provide useful and basic information and knowledge that can enhance the required background for sound relaying basics. In addition, it can enhance the system disturbance analysis process to arrive at the correct time line that makes it possible to isolate the faulted element and restore service to the balance of the power system. The effects on the relaying system are also highlighted, so that the relay system design and its intended function can be optimized.
In this section we document most of these phenomena as they appear on DFR and numerical relay fault records. The power system phenomena and related behaviors of the protection systems are supported by DFR and numerical oscillography records. Involved are generator rotor oscillations with the power system during out-of-step conditions and synchronization events; appearance of 120 Hz in the rotor surface during faults and unbalanced conditions; flow of the third harmonic and its variations in a generator neutral grounding system; negative-sequence current flow in generators; active (MW) and reactive (MVAR) generator outputs during machine terminal faults; inadvertent generator energization; generator loss of excitation; generator-trapped decayed energy; generator neutral zero-sequence voltage coupling through step-up transformer ...