GENERATOR POWER STATIONS


TURN KEY PACKAGED ELECTRICAL SYSTEM

A turn key, packaged electrical system is available for power stations using diesel / gas ignition generators, including design, supply, technical support services for installation, commissioning and after sales service. This includes prime power units either in island mode or connected to the grid at either low voltage or medium voltage. The power stations are designed for automatic, un-attended operation with a fully integrated SCADA system for control and monitoring.

GENERATORS
The generators may be diesel engine powered or gas ignition engine powered with either low voltage or medium voltage alternators. The starting system may be either compressed air operated or battery powered. Air start systems require a duty and standby air compressor and a receiver. Many generators are fitted with an on-board, local, generator start and fault shutdown system. Alternatively, a custom made system may be fitted. The local start and fault shutdown system allows local, manual operation of the generator for maintenance purposes or in the event of the failure of the automatic controls. The electrical system is fitted with safety isolation points. The local start and fault shutdown system is interfaced to a station control panel for automatic operation. The speed controller, load share unit, automatic voltage regulator and automatic synchronizer for each generator are generally mounted in the station control panel. The generators may be installed in an engine hall or individually installed in an enclosure.


ENCLOSURES
The generator enclosures are usually modular and often incorporate acoustic attenuation in order to reduce environmental noise. The enclosures are fitted with cooling fans which run when the engine is running. There may be electrical accessories such as overhead cranes, lighting, a starting battery charger, and socket outlets. The enclosure is fitted with a local distribution board which is used to supply the electrical accessories and any on-board generator electrics such as anti-condensation heaters. The electrics in each enclosure are supplied from the low voltage station auxiliary motor control centre.


FUEL SYSTEMS
The diesel fuel system generally comprises bulk tanks, transfer pumps, day tanks, instrumentation and controls. The bulk tanks are usually tanker filled. A local fuel fill, level control panel is provided for the tanker operator. Fuel metering is sometimes incorporated. The bulk tanks and day tanks require level instrumentation and solenoid controls for valves. The fuel transfer pumps are a dual set, operating in duty / standby mode with automatic rotation of the duty pump. Additional instrumentation may be provided for the day tanks, such as engine supply fuel temperature / flow, engine return fuel temperature / flow, fuel consumption rate and consumption total. The fuel system electrics are extra low voltage 24VDC.


COOLANT SYSTEMS                                                                                                                                                         
The coolant system may be either single or twin circuit. The single circuit cooling system is generally fitted with an on-board radiator. The radiator fan may be either engine driven or electric powered. The twin circuit systems generally have remote radiators with electric powered fans. The fans may be either fixed speed or variable speed. The variable speed fans have a feedback control system so that the speed of the fan is controlled by the temperature of the cooling circuit. The electric powered fans are supplied from the low voltage station auxiliary motor control centre.



INSTRUMENT AIR SYSTEMS

Instrument air systems are sometimes required for the operation of valves in the fuel system. The instrument air system comprises an air compressor and instrumentation to monitor instrument air pressure. The air compressor is supplied from the low voltage motor control centre.


STATION MAIN SWITCHGEAR
The station main switchgear comprises the generator circuit breakers and the feeder circuit breakers. The main switchgear may be either low voltage or medium voltage, depending on the voltage of the generators. If the system is medium voltage, then a step-down transformer is required for the station auxiliaries and consideration must be given to the type of neutral - earth connection. The station main switchgear generally houses the generator electrical protection relays and the current / voltage transformers for the generator speed control, load sharing and synchronizing.


LOW VOLTAGE AUXILIARY MOTOR CONTROL CENTRE
The low voltage, auxiliary motor control centre comprises starters and distribution boards for the station auxiliaries, including the generator auxiliaries.


STATION BATTERIES & CHARGERS
The station batteries and chargers comprise two systems. The first is the station control battery / charger system, which is usually 24VDC. The second is the station main switchgear trip / close battery / charger system, which is required if the station main switchgear is medium voltage. Redundant battery / charger systems may be used to improve availability.


STATION CONTROL PANEL                                                                                                                                                    
The station control panel comprises the station PLC, the SCADA system, automatic controls for each generator and the marshalling panel for field cabling. The station PLC provides control and monitoring of the power station. Redundant PLCs may be used to improve availability. The SCADA provides the operator control, status monitoring and reporting. Remote SCADA control is available. The automatic controls for each generator include the speed control, load share unit, automatic synchronizer, automatic voltage regulator, diesel level controls and operator hardwired controls. The control system is configured with dual levels of control so that the power station availability is maximised. The normal, unattended level of control is fully automatic via the PLC. Should the PLC fail, then the next level of control is semi-automatic control via operator initiation of hard-wired, automatic processes.


PRE-FABRICATED SWITCH-ROOMS
Pre-fabricates switch-rooms are used to house the station main switchgear, the low voltage station auxiliaries motor control centre, the station batteries and chargers, and the station control panel. The advantage of using pre-fabricated switch-rooms is that the site erection and testing work is minimised.


AUTOMATIC UNATTENDED MODE
Automatic, unattended operation is the normal mode of control. The station is controlled by the PLC. Generators are sequenced on and off line depending on the station load. The operator may select and deselect generators for available operation via the SCADA.



ISLAND MODE
                                                                                                                                                                          
In island mode, the station operates independent of the grid or any other power station. The station frequency is isochronous and the voltage has zero droop from no load to full load.


GREY START MODE
In grey start mode, the station is off-line and grid voltage is on the main bus of the station main switchgear. The station is started by synchronizing generators to the grid. The grid is disconnected once the required generation capacity is on-line. In grey start mode, the generators follow the grid frequency and voltage as they are synchronized to the grid. Once the grid is disconnected, the station reverts to isochronous operation with zero droop voltage.


BLACK START MODE
In black start mode the station is blacked out and there is no voltage on the main bus of the station main switchgear. The operator selects the required number of generators for black start via the SCADA. The first generator on-line is closed onto a dead bus. The remaining generators go on-line by synchronizing to the first generator. The station is in isochronous operation with zero droop voltage.


IMPORT / EXPORT MODE
The import / export mode is used if the station is to operate in parallel with the grid or another power station. An inter-connector circuit breaker is required in the station main switchgear. The station control panel requires a master controller to provide the automatic functions of synchronization to the grid and import / export control. The operator initiates the functions via the SCADA.



PLC & SCADA SYSTEMS
                                                                                                                                                           
The PLC provides the control and data acquisition functions for the station. Redundant PLCs may be provided in order to improve the station availability. The SCADA system allows operator control and monitoring either locally or from a remote location.


DOCUMENTATION
Documentation required for the electrical package of a diesel generator power station project includes:
- Test records and certificates
- Pre-commissioning and commissioning records
- Hand-over documentation, "as installed" drawings
- Operation and maintenance manuals
- Spare parts manuals
The documentation is provided in hard and soft copy.


DESIGN
A complete range of electrical design services is available for diesel generator power station projects. The services range from cost estimates and preliminary concepts to detailed electrical schematics and procurement, according to the needs of the project. Please refer to the section describing electrical engineering services for more details.


LOAD TESTING
The load testing of the generators is required to prove that the generators meet the site rated load capacity. The generators are tested individually on either a load bank or site load, depending on the site conditions.


FACTORY ACCEPTANCE TESTING
Factory acceptance testing of the electrical package is an important milestone. It proves the bulk of the functionality of the main components, such as the station main switchgear, the low voltage auxiliary motor control centre, the station control panel and the battery / charger systems. Not all functionality can be proved because the total package cannot be interconnected and because generators and other components may not be available. The factory acceptance testing of each item involves routine testing as per the relevant standard and functional testing


SUPERVISION OF SITE ERECTION                                                                                                                                       
The supervision of site erection allows the day-to-day co-ordination of the electrical installation between the main contractor, the electrical contractor and the generator contractor. The co-ordination minimises delays in construction that may otherwise be caused by misinterpretation of the drawings, unexpected problems which occur on site and by providing site guidance as to the sequence of work. The supervision of site erection allows in process testing as portions of the work are completed.



SUPERVISION OF SITE PRE-COMMISSIONING

The supervision of site pre-commissioning allows day-to-day co-ordination of the pre-commissioning between the main contractor, the owner and the generator contractor. The co-ordination minimises the delays in pre-commissioning by providing site guidance and by addressing immediately any defects which may be identified.


SITE ACCEPTANCE TESTING
Site acceptance testing is the proving of the installation for hand-over to the client. The tests are mutually agreed between the client and the generator contractor at the time of order. The tests generally require rigorous proving of the functionality of the diesel generator power station and a proving run under normal operating conditions.


REFURBISHMENT                                                                                                                                                               
On occasions, the client may have second hand switchgear which it is intended to be used in the power station. In such cases, it is necessary to provide a technical evaluation of the switchgear and supervise the refurbishment of the switchgear.


TRAINING
In order to provide optimum performance, the electrical portion of the diesel generator power station requires operators and maintenance personnel to have a proficient knowledge of the system. Therefore, training is necessary for the operators and maintenance electricians.


QUALITY ASSURANCE
Quality assurance is either based on the client's in-house procedures or is prepared to suit the scope of work required for the project. The quality assurance is in accordance with IEC standards. The relevant procedures are prepared and implemented as required.

STANDBY / GRID CONNECTED GENERATOR POWER PLANTS

A turn key, packaged electrical system is available for standby / grid connected generator power plants using diesel / gas ignition generators, including design, supply, installation, commissioning and after sales service. This includes standby power units in island mode or grid connected generators at either low voltage or medium voltage. The power plants are designed for automatic, un-attended operation with a fully integrated SCADA system for control and monitoring.

STANDBY AUTOMATIC MAINS FAILURE CONTROLS
Standby, automatic mains failure controls allow the change-over from grid power to standby generator power and vice versa. The generators may be either single units or multiple units operating in parallel. The generator voltage may be either low voltage or medium voltage. The change-over may be "bump less" i.e. without a break in supply to the load.


GRID CONNECTED POWER PLANTS                                                                                                                                  
Grid connected, diesel generator power plants are either prime power units continuously on-line or power plants which are put on-line for peak lopping. The units follow the grid frequency and voltage. The power plant exports power to the grid.