ECHSR

Steam turbine governor with duplex architecture.

Purpose

"PromAvtomatika" developped the governor with duplex architecture for turbine K-225-12.8. This system can replace the hydraulic system of control for steam turbine and is aimed on automation of control for the electric and thermal load on the trurbine in all modes.

Basic functions

• control for the state of four high pressure, four middle pressure and two low pressure valves of the steam turbine.
• mode of automatic regulation for electric power with frequency task correction in the energy system. The final task and power change speed are entered either automatically or by operator according to dispatcher schedule.
• mode of regulating the pre-turbine fresh steam.
• mode of sliding pressure with set opening of turbine"s valves.
• mode of regulating turbine"s rotor rotating speed.
• automatic regulation of pressure in the process of thermal screening.
• automatic turn of the rotor up to nominal frequency with intermediate detention and accelerated critical zones passing.
• limiting regulation of fresh steam minimal pressur, maximal pressure in the control step of high pressure cylinders, maximal pressure in the thermal screening process.
• automatic unloading according to block automatic signals.
• keeping the rotating speed of the rotor within the set limits at the electric load reset.
• forming signal for turbine"s shutdown in case of appearing illegal values of turbine"s speed and acceleration
• automatic selection of load change speed depending upon thermostressed state of rotors" high and middle pressure cylinders.
• monitoring of actuating fluid parameters and basic equipment state.

Governor structure

The system includes control panel itself and operator"s station.

Control panel includes control means and should be installed in the blocking automatic machinery room of the electric power station. The panel contains two identical hardware control channels. One of them controls the turbine, another is kept in hot standby. Controlling channels are galvanically isolated from each other and from the outer lines.

Switching control from one channel to another is implementerd by commutation of output lines with relay (switching time not more then 3 milliseconds). Control for switching relay is done by a special "arbitre" device, whichreceives diagnostic signals from eboth channels. Depending on these signals the "arbitre" takes decision about the channels up-state. In case of leading channel malfunction transfers control to the standby channel. Such important usage of "arbitre" requires high reliability, that is why the arbitre is manufactured as a triple set.

For the bumpless switch from one channel to the other the channels controllers implement continous information exchange via the channels in series.

Each channel is supplied with a panel sensor monitor ensuring control loop settings adjustment, turbine modes control.

Hardware set of control channels

Each channel includes the galvanic bypassing of outer input and output signals, main controller, valves positioning units, current forming units for electro hydraulic commutators, bias current stabilizers, standby power system.

The base of control channel is a microcontroller MicroPC format. It implements the basic control algorithm. Control program loop length is 0,001 sec. The controLling program is developed under POLYGON development environment.

Positioning blocks are implemented for positioning turbines valves according to each valve"s character. Positioning units are microprocessor regulators with controlling loop length 0,001 sec. Their feedback are oil pressure in the control line and state of valves servodrives plungers.

Positioning unit forms acontrolling signal 4-20 mA which is transmitted to the current driver. Electro hydraulic transformer current driver is a terminal element transmitting the controlling system effect to the electrohydraulic transformer servodrives of high / middle / low pressure valves. Thus, there is no necessity in a current control module and speed and pressure selection valves unit.

Operator"s station

Operator"s station on the basis of industrial PC is set in the block control panel room. Connection to the panel is implemented via Ethernet network. Operator"s station is a convenient and clear interface as a symbolic circuit on the computer screen where an operator can check the measured parameters values or change the working mode of a turbine. The operator"s station also includes the minimal set of electromechanical control elements connected direct to the control panel in case of computer"s breakdown.