6.7          LIGHTING AND MAINTENANCE NETWORK

6.7.1      Lighting

Several lighting subsystems will be adopted in this project:

Ø       -Normal AC Lighting System

Ø       -Normal Emergency (N/E) AC Lighting System

Ø       -DC Emergency Lighting System

Ø       -Safety Lighting

6.7.1.1    AC Normal Lighting System

The Normal AC lighting System will provide lighting of the plant. And the normal lighting voltage will be AC 230V.

In order to maintain the voltage quality of lighting network, in main block, lighting power supply will be separate from auxiliary power system. One on-load tapping changer lighting transformer and corresponding 480/240V bus will be installed for each unit, serving for unit normal AC lighting.

Power of lighting in auxiliary workshops outside the main block will be supplied from LV switchgear nearby.

6.7.1.2    AC Emergency Lighting System

AC emergency lighting system will be installed in the main block for each unit and supplied from unit 480/240V emergency bus. In normal operation, the system will be fed from corresponding unit PC to form part of the normal lighting of the plant, when the normal power is loss; it will be fed by AC emergency power system.

6.7.1.3    DC Emergency Lighting System

The DC Emergency Lighting will be provided in the control room, battery room and diesel generator room. Except keeping lighting in the control room, the DC Emergency Lighting will not be put to use under the normal operation condition, only on the condition of all AC lighting power fault, it will be put to operation automatically and supplied from DC bus of battery.

At exit and entrance, and auxiliary workshop far from main block, emergency lighting will be provided by self-contained battery lighting fixture assemblies.

6.7.1.4    Safety lighting

In special area such as for boiler maintenance lighting, 24V voltage will be applied.

6.7.1.5    Lamp and light source

Embedded type of fluorescent lamp sets will be adopted in central control room. Different type of lamp will be adopted such as fluorescent, floating type, widely type, waterproof, dustproof, explosion-proof, and so on.

6.7.2      Maintenance network

In main block, one LV maintenance transformer and one 480/240V maintenance bus will be furnished to feed the maintenance network and crane equipment.

In auxiliary shops, the maintenance source will be fed from 480/240V MCC bus nearby.

6.8        Cabling

6.8.1      Cable Selection

6.6kV and 480/240V power cable will be copper core, XLPE insulated type with PVC sheath.

Control cable will be copper conductor, polyvinyl chloride insulated type.

6.8.2      Cable Structure

The following cable structure will be adopted in the project:

In main block area, the overhead cable tray and cable trench will be adopted.

Cable trench will be adopted in plant area.

6.8.3       Cable Fire-Proof Design

C type flame-retardant cable will be applied in main block, coal handling system & other inflammable area.

To prevent the spread of fire, following measurement will be adopted in cable raceway as necessary:

Fire-resisting plate is adopted in the sector of main block cable tray where fire easily happens.

Effective fire-against safeguard of sealing will be adopted in cable structure.

Hole for cable access under panel will be sealed by fire-withstand material.

Necessary smoke and temperature detection & fire apparatus will be installed.

6.9 DC System and UPS

6.9.1      DC System

One set of 220V DC system will provide power for control, protection, emergency lighting and emergency load etc. of unit and substation.

Each DC system will comprise two banks of battery , two 100% rated chargers and DC distribution boards.

DC system will be an ungrounded system. The ground detect device will be provided to detect which circuit is grounded.

The battery will be valve controlled lead-Acid type, and charger will be high frequency switch type.

Batteries will be capable of supplying the total emergence power load for a period of 1 hour without AC source.

6.9.2       UPS

For the power of the critical load such as DCS system, transducers, automation device and intelligent device etc, the UPS system will be provided.

UPS equipment will consist of rectifier, inverter, static change-over switch, by-pass switch, isolation transformer, voltage-adjusting transformer, transducer and electronic elements etc. UPS shall be rated to supply the total load for a period of 1 hour in the event of loss of normal supplies.

6.10       Excitation System

The static Excitation system will be provided. The excitation will be provided by a static shunt excitation system consisting of excitation transformer, thyristor rectifier device, automatic voltage regulator device (AVR), field breaker device, over-voltage protection device, excitation-starting device etc. The AVR will be digital type and have dual automatic channels with a follow-up control to ensure a smooth change-over from one to another. AUTO/MANNUAL control mode will be provided. The supplementary functions including over-excitation limit, under-excitation limit, PSS etc. will be provided in AVR as well.

6.11 Secondary Wiring

6.11.1     Control

The unit electrical control system will be monitored and controlled by DCS, such as generator, setup transformer, start-up/standby transformer, unit auxiliary transformer, DC system, UPS system in the CCR. The operator can operated all station electric system through the DCS operator stations.

The 110kV substation will be monitored and controlled by the integrated substation automation system (SAS). 110kV bus equipment, 110kV lines, etc will be monitored and controlled by SAS. SAS provides data acquisition and disposal for digital, analog and pulse value, metering, display, alarm, print, recording the sequence of event, previous occurrence review and recording, synchronize, control and operation.

6.11.2     Protection

Duel redundant micro-processor based protection will be provided to the each generator-transformer group, including generator differential, main transformer differential, unit transformer differential and backup protections.

Duel redundant micro-processor based protection will provided to the startup/standby transformer, including transformer differential, backup protections.

For mid voltage system, the microprocessor based device will be used to protect the feeders and motors.

6.11.3     Synchronizing Systems and Quick Power Change

Automatic synchronizing Systems will be provided for generator

For power change of mid-voltage bus, quick power change device will be provided

6.12       Coal Handling PLC Control System

A PLC Control System will be provided to control and monitor the coal handling system. It will comprise of the PLC stations, operator stations, remote I/O, relay panels and CRT monitoring system. Industrial TV Monitoring System will be adopted for coal handling system.

6.13       Fire Detection and Alarm System

The Fire Detection and Alarm System will be provided. The system will be composed of central alarm control panel, local detector, and so on. The fire detect area will include control room, switchgear room, and cable tray etc.