Power

Power
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Selasa, 05 April 2011

Unit Master


Unit Master

Controls
Speed control, load control and pressure control is selected base on priority.
During start-up, the priority is turbine speed, whatever the load and pressure. The speed is controlled by governor and after synchronized, the governor setter automatically follows to the value a little bit lower than a load limit set value.


Load control is the priority the MW output, this controls selected when normal operation. The load limit setter automatically follows to the value a little bit higher than the flow demand. The turbine speed or frequency is controlled by dispatcher by ordered power stations to rump up or down the load.

Pressure control is automatically selected when the unit got trouble like unit run back or unit goes to house load after load rejection. The priority is the main stem pressure whatever load output to maintain the stabilization of unit. It means the load is followed how much the main steam pressure. The turbine speed or frequency is still under controlled by dispatcher.

Modes
The standard mode is coordinate. If load set is change, unit control will rump up or down the fuel flow, then delay to turbine load rump up or down.


If the turbine master does not follow the request of unit control, it will switch over to boiler follow mode. It means turbine master is on trouble and set to manual, and boiler is following what ever turbine master set.
Example: External set point for turbine load is not active.

If the boiler master does not follow the request of unit control, it will switch over to turbine follow mode. It means boiler master is on trouble and set to manual, and turbine is following what ever boiler master set.
Example: All feeders set manually.
Exception: The initiation of unit run back will result in an automatic switch over to turbine follow.

During start up and shut down the unit, turbine and boiler are controlled separately by operator is called base mode.

Unit Master LFC & ALR


The highest hierarchy is Load frequency Control (LFC). If LFC is selected, the power station load rump up or down is based on fluctuating of the frequency grid. In the steam power station usually limitation of load compensation up or down from load set is 5 MW to stabilize the frequency.
Click here for more information about LFC in bahasa


Below LFC is Automatic Load Regulator (ALR) Control. The ALR is set by power station operator, and the frequency grid is controlled by dispatcher. When frequency increase, the dispatcher order to power station operator to reduce the load, and also vies versa.

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