We currently possess a total of 10 GE Frame type Gas Turbines in our power plant, consisting of 7 units of Frame 5P and 3 units of Frame 6B. These turbines are interconnected and operate on the Mark VIe system with the Ex2100e excitation system.
The load control method employed is "PRE SELECT," while the PF/VAR control is set to a power factor (PF) value of 0.92, typically. Speed control is achieved through the implementation of a droop mechanism, and the excitation regulation mode is set to "Auto." Moreover, our power plant operates in a simple cycle configuration.
Recently, we experienced a plant blackout due to a tripping incident at the distribution substation. As a result, approximately 150MW of load was rejected at the downstream. Surprisingly, the gas turbines continued to operate at the pre-selected value instead of activating the droop control mechanism to reduce the frequency in response to the excess power generation caused by the load rejection event.
Throughout the event, the frequency of all gas turbines was observed to gradually increase from 50Hz to 51.85Hz over a span of 4 minutes, as recorded in the Historian. The over-frequency protection feature in the G60 Multilin relay was then triggered, leading to the tripping of the 52G breaker and causing all units to run at Full Speed No Load (FSNL) condition. Ultimately, this event resulted in a blackout affecting the stakeholders of the refinery plants.
I am seeking insights into the reason why the droop control mechanism failed to operate during this event. Additionally, I would appreciate any suggestions on preventive measures we can implement to avoid such incidents in the future. One potential approach could involve switching some units to Part Load Control mode and assigning one unit to Isochronous mode to effectively respond to frequency fluctuations perhaps?
The load control method employed is "PRE SELECT," while the PF/VAR control is set to a power factor (PF) value of 0.92, typically. Speed control is achieved through the implementation of a droop mechanism, and the excitation regulation mode is set to "Auto." Moreover, our power plant operates in a simple cycle configuration.
Recently, we experienced a plant blackout due to a tripping incident at the distribution substation. As a result, approximately 150MW of load was rejected at the downstream. Surprisingly, the gas turbines continued to operate at the pre-selected value instead of activating the droop control mechanism to reduce the frequency in response to the excess power generation caused by the load rejection event.
Throughout the event, the frequency of all gas turbines was observed to gradually increase from 50Hz to 51.85Hz over a span of 4 minutes, as recorded in the Historian. The over-frequency protection feature in the G60 Multilin relay was then triggered, leading to the tripping of the 52G breaker and causing all units to run at Full Speed No Load (FSNL) condition. Ultimately, this event resulted in a blackout affecting the stakeholders of the refinery plants.
I am seeking insights into the reason why the droop control mechanism failed to operate during this event. Additionally, I would appreciate any suggestions on preventive measures we can implement to avoid such incidents in the future. One potential approach could involve switching some units to Part Load Control mode and assigning one unit to Isochronous mode to effectively respond to frequency fluctuations perhaps?