7  C&I SYSTEM

The design scope of C&I system in this project includes all the systems of measurement, control, interlock, protection and alarm, for one 200MW unit which cover boiler, turbine, generator and their auxiliary systems and auxiliary workshops of the plant.

A boiler-turbine-generator centralized control mode will be adopted in this project. The DCS is adopted for unit control. It is capable of performing those functions such as monitoring, controlling and management etc. during the boiler-turbine-generator and its auxiliaries in start-up, shut-down and operation.

A distributed control system (DCS) will be adopted for monitoring, controlling and managing the unit and its auxiliaries in central control room (CCR) to ensure the safety, reliability and economic operation of unit.

The programmable logic controller system (PLC) will be adopted for monitoring, controlling and managing the auxiliary workshop in local control room, such as boiler make-up water treatment system, ash handing system etc.

FGD control system is made up of following parts:

Distributed control system of FGD,

Automatic fire alarm system,

Industry Television system ,

Continuous emission monitoring system,

The power system of I&C.

The unit and its auxiliaries will be monitored and controlled by a distributed control system (DCS) through the operator workstation in the central control room (CCR). A few conventional instruments and control devices which serve as emergency backup during DCS fault are mounted on the auxiliary control panel or the console in the central control room.

The control system is capable of managing the unit and its auxiliaries by operators and assistants (the duties of the assistant operator would include: assisting unit startup; local operations and routine running checks etc.). Operators can make a start-up (associated with local assistant), shut down and emergency handling for unit in CCR. At a normal operation, monitor and control of the unit will be performed mainly through the DCS interface devices (LCD/Keyboard etc.) on the console. Emergency shutdown devices (hard wired) at central control room will be provided to ensure the safety of the equipment and personnel.

Local workshop centralized control mode based programmable logic controllers (PLC) and upper computer where necessary will be used in boiler make-up water treatment plant (including Industrial Waste Water Treatment), Ash Handling Plant, Complex Water Pump House, etc, where local control rooms will be provided for mounting control devices.

The PLCs will have communication interfaces to the DCS.

DCS to fully cover all the process directly related to the start, shut-down, and the operation of the unit. PLC could be adopted for the equipment/sub-systems.

The control system of auxiliary boiler will be supplied with the main equipment, it is adopted local control mode. The control device will be arranged in the auxiliary boiler house.

The boiler-turbine-generator units and their auxiliary system plus the associated electric system and equipment will be controlled, monitored and managed in CCR. The CCRs elevation is the same as the turbine operation floor. The CCR will be accommodated with consoles, auxiliary control panel, fire alarm panel, shift supervisory desk, printers, etc.

There are electronic equipment rooms adjacent to the CCR, where will be placed C&I power cabinets, relay panels, DEH cabinets, ETS cabinet, TSI cabinet, DCS cabinets etc.

Under CCR and electronic equipment rooms there are cable cabins.

The DCS proposed will be specifically designed for power plant applications. The technology will be microprocessor based, utilizing proven hardware, firmware and software. The architecture of the system will allow for the control functions to be economically distributed within system modules to satisfy the system design criteria.

It will be identified the Version or Release Number of the proposed DCS. The same Release Number of DCS (and the proposed interfaces to other proprietary control systems) will have been applied in their entirety for similar applications and have achieved at least 2 years of relevant satisfactory operation on other projects.

In general terms the DCS system will feature:

l           Independent process controllers utilizing intelligent I/O hardware, terminations and signal conditioning as required. The process controllers will be redundant and perform the necessary continuous, discontinuous, sequential control, protection, alarming and data acquisition functions.

l           VDU-based operator workstations in the central control room, including keyboards, pointing devices, printers and monitors with graphic capability.

l           Configuration and programming units consisting of color graphic VDUs with keyboards, printers, removable and fixed disks.

l           Redundant communication paths between elements of the system (functional processors, operator and engineering workstations) over a high speed data highway. Extensive diagnostic procedures will be provided to ensure error free performance.

l           Interactive process-oriented software for the development of the control and monitoring functions. Standard high-level languages will also be available for user programming.

l           All software to provide the functions required.

Each system element will be designed such that the failure of any one element will not affect the operation of any other element nor requiring the outage of the running element to repair the faulty element.  The same hardware will perform both data acquisition functions and modulating control, protection and sequential logic. This system will be expandable and flexible, able to be configured for a wide range of process applications and easily field changeable via engineer-oriented software.

The controls will be functionally distributed. It will be possible to implement redundant controllers with automatic take-over by the redundant device on failure of the primary device. Controller redundancy will be provided in a one to one fashion. A processor failure will be alarmed on the operator's console.

High-speed data communications are to be handled independently of the functional processors. Each functional processor will be programmed to execute its assigned tasks with no communication overheap. Security of communications will be assured by use of a proven highway protocol and system diagnostics. Each element will have universal access to all process point variables within the system.

All communication paths and interfaces will be fully redundant; this includes communication within the DCS and communications with non-DCS devices and subsystems. The changeover to the redundant link will be bumpless and automatic; when changeover takes place, owing to a failure, an alarm will be generated. Non-active links will be continuously monitored for healthy status and alarm raised if a failure is detected.

It will be provided generic documentation on the proprietary DCS system proposed, together with a fully detailed functional specification for the DCS. A statement of OSI compliance for the communication interfaces will also be provided.

The functions of DCS are included as following:

l           Data Acquisition System (DAS);

l           Closed-loop Control System (CCS);

l           Sequence Control System (SCS);

l           Burner Management System (BMS).

The management information system will be designed to provide “read only�?access to all working and archived data on the unit DCS systems. It will give access to current operational displays including the alarm display, DCS diagnostic displays, logs. It will have allowed the user to format and create logs and trend displays and generally manipulate the data on the system. It will be possible to generate trends of process parameters with a selectable sampling rate of up to 10 samples per second.

The Managers Work Stations (MWS) will consist of standard desk top PC’s. These will be linked to an independent communication network linking all offices within the administrative building and Control Buildings. The number of terminals to be provided under the Contract and there provisional location will be as follows: -

----- Two (2) Terminals located on the Supervisors Desk in CCR

----- Some Terminals located in the administrative building

The network will have the capacity of driving at least twice the number of terminals specified.

Turbine control system will adopt DEH (Digital Electro-Hydraulic) control system. For the DEH having a high reliability.

The functions of DEH are included as following:

Remote control turbine shut down, setting static relationship of the servo system, speed and load control, main steam pressure control, over speed protection, run back, primary frequency regulation etc.

Turbine supervisory instrument (TSI) is used to monitor all kinds of parameters of locally mounted turbine instruments, including differential expansion, axial displacement of rotors, vibration of shaft bearing, speed etc.

The unit will be open-loop controlled by ETS (Emergency Trip System) through measurement loop, adjustment device, switch-over device, actuator and monitoring important parameters of unit to ensure safe operation of the unit.

Measurement of plant process parameters utilizing signal-transmitting instruments such as sensors, process switches, thermocouples, RTDs, transmitters, etc. will be provided to support the control, monitoring, alarm and protection as well as for plant and equipment performance calculations. The transmitters and analyzer will adopt smart type. Local indicators, such as pressure gauges, thermometers, level gauges etc will also be provided for maintenance, local monitoring and operation.

Local instrument, control box and control panel could be provided near the process equipment.

Protection boxes could be provided for the outdoor field instrument.

All cabling on the plant will be flame retardant. All equipment requiring cable connections, such as transmitters, equipment housings, actuators, marshaling cubicles, will be fitted with cable glands of the correct size and number to accept the necessary cabling. Marshaling cabinets mounted in the plant area will have a minimum enclosure rating of IP54.

Power distribution cabinet of C&I system will provide the driving force and control power for various motor driven valves with line voltage 480V AC, and redundant power supply mode will be adopted.

For C&I system there will be an Uninterrupted Power Supply system (UPS) of voltage 240V AC. All instrument and control power supplies will be connected directly to the UPS.

DC control power for the units will be 220VDC (if necessary), each of them are supplied with redundant circuits respectively and connected from battery DC system of the unit.

Compressed air for pneumatic actuators and pneumatic control valves etc will be supplied from special air supply facilities consisting of air compressors, filters, air receivers and dryers, etc. The pressure of air supply from the compressors is about 0.8MPa. Air receivers are mounted to ensure the reliability of air supply. The volume of air receiver can offer the compressed air that C&I devices need when all air compressors are out of work more than five minutes.