Inside the ABC is also equipped with Supervising Instrument Boiler in the form of recorder recording data - boiler operation data. The ABC system has functions for operation and thermal power plant control as follows:
Structure of the ABC system:
The ABC system is composed of a microprocessor with high reliability and maintenance levels. These tools or control modules are installed in 4 cabinet systems with a power supply. 2-wire electric transmitters and pneumatic actuators are used in this ABC system.
The buttons and operating indicators for the master unit of the ABC system are attached to the Master Console Unit installed on the BTG board in the Central Control Room (CCR). Signal devices from the ABC system are also installed in the Master Console Unit.
DCS microprocessors are provided for manual operations and auto / manual transfers. This control station is installed on the BTG Board at the CCR. For plant protection, limits are given such as cross limit, minimum fuel, pressure limit and safety interlock in system failure. The ABC system has a complete function for automatic plant operations with interfaces needed for ABS, EHC and other control systems.
Design for Hardware
1. Cabinet System
The cabinet system of the ABC system consists of 4 cabinets. The cabinet system includes a power supply unit with NFB, control modules, relay modules and terminal units. Abnormal indications of LEDs from the detailed failure of the ABC system are arranged in the cabinet system.
2. Master Console Unit (UMC)
Operations and monitoring of BTG units can be carried out through the Master Console Unit. This console is arranged at the BTG Board in the central control room.
3. Digital Control Station (DCS)
Microprocessor Bailey based on Digital Control Station (DCS) is used for control stations. DCS compilation is shown in figure 4.6. All DCS are installed on the BTG Board in the CCR. The output tracking indication lamp is set up on the DCS front panel to indicate auto-standby or manual operation prohibition conditions. When the light is on, either automatic or manual operation is not available, since the fix signal is operated by interlock. When the lights are off, automatic or manual operations are available as well as AUTO / MAN transfers.
Pneumatic actuators are used for ABC systems except the HP Turbine Bypass Control valve.
2-wire electric transmitter is used for control measurements. The Oxygen analyzer from NGK is used to control O2 exhaust gas in the air flow control sub-loop.
6. Power supply
The power sources used in the ABC cabinet system are as follows: a) 110V AC from “CVCF” b) DC 110V from “110V D / P units”
7. Interface for external signals
Basically a hard wired connection is used on analog and digital input/output on the ABC system.
Boiler-turbine coordinate control:
With this method the boiler and turbine are controlled at the same time. The output generator is controlled by fuel flow (or master boiler) according to the output demand and main steam pressure controlled by the turbine governer with MW deviation compensation. Therefore both boiler load and turbine load are able to keep up with changes in output demand.