Governor Messages

Governor Max Limit Messages

"Diesel Gov1 on Max Limit."

"Gas Turbine Gov1 on Max Limit."

"Steam Turbine Gov1 on Max Limit."

"Woodward Steam PID1 on Max Limit."

Description – Governor models control the mechanical power delivered to the shaft of a generator. If the generator is asking for more power than can be supplied by the prime mover, this message will be generated at initialization. Note that whenever a governor reports this condition, a steady-state run will not be steady-state. The power required by the system is not being met, and the governor is on a limit. As soon as your simulation begins, other generating units in the system will have to pick up the extra generation needed to balance out the system.

Fix - Reduce the power output of the generator in the power flow or increase the max limit setting in the governor model to remove this warning.

Governor Min Limit Messages

"Diesel Gov1 on Min Limit."

"Gas Turbine Gov1 on Min Limit."

"Steam Turbine Gov1 on Min Limit."

"Woodward Steam PID1 on Min Limit."

Description – Governor models control the mechanical power delivered to the shaft of a generator. If the generator is asking for less power than can be supplied by the prime mover, this message will be generated at initialization. Note that whenever a governor reports this condition, that a steady-state run will not be steady-state. The power required by the system is not being met, and the governor is on a limit. As soon as your simulation begins, other generating units in the system will have to reduce generation to balance out the system.

Fix - Increase the power output of the generator in the power flow or decrease the min limit setting in the governor model to remove this warning.

Note: Typically for a min limit message to appear, either erroneous data has been entered for the governor model, or the generator in the power flow case is absorbing power. The min limit for most governor / prime mover models is zero. This simply states that the prime mover will not become a load. In actual practice, the min limit is often set to the level of turbine power output that would trip the reverse power relay, or some other form of minimum power protection. These messages thus alert you to an improper initialization, where the unit would have actually tripped offline.

Governor Runtime Load Limit Messages

"Gas Turbine Gov1 Now ON Ambient Temp Load Limit."

"Gas Turbine Gov1 Now OFF Ambient Temp Load Limit."

Description - As for Max Limit messages discussed above, this message is supplied (typically during run-time) when a unit is being over-loaded. This can happen during a contingency, where there is a major loss of generation and remaining units must then pick up the load, forcing them into an overload condition. The load limit in this case performs automatic control, causing the generator’s gas turbine not to continue in overload. The messages supplied inform you when the turbine goes into and out of load limit control.

Fix – Though this is a message simply noting a control action, if you want to keep this message from appearing (meaning you want to keep the turbine from moving into a temperature load limit condition), then create a system contingency that does not have a large imbalance of load requirement vs. available generation. Create a condition where load and generation are balanced, and where generation has some headroom (generator capability greater than load requirement). Alternatively, since the temperature load limit takes time to be reached (time constant simulates how the turbine heats up over time when in an overload condition), only enable overload conditions that have a duration and level that will not cause the unit to reach the temperature load limit.

Governor Initialization Load Limit Messages

"Exceeding Ambient Temperature Load Limit at Initialization."

Description - As for Max Limit messages discussed above, this message is supplied (during initialization) when a unit is over-loaded. Since the governor is limited, upon running a simulation, the generator will be forced to a lower power level, creating a non steady-state response if run steady-state.

Fix - Reduce the power output of the generator in the power flow or increase the max limit setting in the governor model to remove this warning.

More Information

Dynamic Stability
Messaging