Modern Buildings essentially implement the needs of Diesel Powered Electricity Generation Plant. It would become an integral part of the building the day building occupied by its tenants. Here we look into what are the objectives, specifications, services to be considered for functioning complete Diesel Powered Electricity Generation Plant installed in a commercial Building.
Performance Objectives for Diesel Powered Electricity Generation Plant
Provide fixed Diesel driven LV Emergency Power Generation Systems at the following site conditions: 50 degrees C. maximum ambient temperature, allow for operation at 0.0 m to 500 m above sea level, taking into account any applicable de-rating factors. The generator set is for standby use with limited time rating as defined in BS7698 with performance class G2.
A complete functioning system shall be delivered, installed and commissioned, which shall include all necessary ancillary systems for combustion / cooling air supply, exhaust air, engine exhaust, fuel supply, power delivery and controls. Every individual building / tower shall have its own standby generator sets.
Manufacturer shall have been regularly engaged in manufacture of the generator sets and associated equipment of types, sizes and ratings required, whose products have been in satisfactory use in similar service for not less than 10 years. Preference shall be given to local manufacturers and agents / suppliers.
Installation firms shall have been regularly engaged and qualified with at least 5 years of successful installation experience on projects with electrical installation work similar to that required for the project.
Submit installation drawings showing plan and elevation views with overall and interconnection point dimensions, fuel consumption rate curves at various loads, ventilation and combustion air requirements, and electrical power and controls diagrams with schematic and interconnection diagrams.
Submit product data showing model numbers, dimensions, weights, ratings, interconnection points, and internal wiring diagrams for engine, generator, control panel, battery, battery rack, battery charger, exhaust silencer, vibration isolators, fuel tank, sound attenuation, sand filter, radiator, and BMS interface.
Manufacturers shall submit detailed calculations to show the generator set output power can be achieved with the installation arrangement and details shown in the drawings, particularly taking into account the arrangement of the air supply / ventilation and exhaust systems.
The contractor shall coordinate all requirements and make due allowance for moving and installation of the generator to its final location. Necessary provisions shall be made to allow for vibration / acoustic isolation of engine-generator set.
Submit manufacturer's installation instructions, operation and maintenance data, include instructions for normal operation, routine maintenance requirements, service manuals for engine and fuel tank, oil sampling and analysis for engine wear, and emergency maintenance procedures.
Design Parameters of Diesel Powered Electricity Generation Plant
The generator set operational limits shall be within the parameters specified for performance class G2 of BS 7698. Generator set shall be assembled with all equipment mounted on a skid type rigid steel bed frame. Design is to permit easy operation, maintenance and repair.
Vibration reduction is to be achieved by appropriate design and careful balancing at factory. Provide approved anti-vibration isolators of steel spring or resilient neoprene between rotating equipment and bed-frame, limiting transmission of vibration to building to a maximum of 0.04 mm amplitude throughout the operating vibrations frequency range.
Noise reduction is to be achieved by exhaust silencing as specified, sounnd attenuators for air inlet and outlets and sound absorbing wall lining shall be used as necessary. Coordinate with the structural design to ensure the noise level inside the building does not exceed the specified internal sound levels.
Engine is to be fully equipped to start and pick up initial load specified at specified minimum ambient temperature. Provide coolant heater. Cold starting aids, such as engine jacket water heater, lubricating oil heater, intake-air heater, battery and all devices, accessories, connections, thermostatic switches and off-duty disconnects with pilot lights and necessary protection, are to be supplemented as recommended by the manufacturer and approved.
Generator voltage, current, frequency, active power (kW), reactive power (kVAR), and battery voltage are all to be monitored via the BMS.
Equipment ratings are to be as shown on the Drawings or the next higher standard ratings provided by the manufacturer, which shall be obtained under local climatic conditions with ambient of 52 deg. C and 100% relative humidity. The nearest standard module size for this duty shall be selected after taking into account all relevant de-rating factors and auxiliary power consumption. Full account shall be taken of the nature of the loads particularly motor loads such as air conditioning, fans, pumps, and non-linear loads such as UPS, etc. that are likely to be connected to the generator.
System Description of Diesel Powered Electricity Generation Plant
The generator system shall be a complete functional system comprising of but not necessarily limited to, the following components and / or sub-systems:
- Diesel generating set, with associated auxiliaries, exhaust system, start-up system, cooling system, fuel system, batteries and charger etc.
- Fuel storage and transfer system.
- Instrumentation, protection and control equipment.
- Outdoor enclosure.
- Manually operated overhead hoist.
- Inter-plant cabling and wiring.
- Connection to BMS system, including all necessary interface elements as detailed in other sections, BMS schedules and / or shown on the Drawings.
Main Components of Diesel Powered Electricity Generation Plant
The generator set shall consist of diesel engine, brushless synchronous generator with direct flexible coupling to engine and single control cubicle as required and shown on the Drawings. Governing is to be to ISO 3046, electronic type governor with limits of speed control as specified.
Starting and Stopping: When in the automatic mode the set is to start and stop automatically by a signal sensed through an auxiliary contact in the load transfer switchgear. The set is to stop, after an adjustable cool-down period (2 - 30 minutes).
Duty: Plant is to reach full speed within 10 seconds from start impulse and accept immediately 60 percent of net rated output (load being mixed, steady and inductive, with motor starting loads as shown on the Drawings). Transient voltage variation is not to exceed 10 percent under any step-load application for which the system is intended, up to full rated load, recovering to within +/- 2 percent within a few cycles.
Failure To Start: Should engine fail to start following a start impulse, the system is to come to rest for a few seconds. Two further starting attempts are to be automatically made with intermediate 20-second maximum periods of rest. Should the set fail to start after 3 attempts, an alarm is to sound and a 'start failure' signal illuminate.
Hand operation shall be possible for testing or normal operation through a test / manual / off / auto selector switch.
Routine operation: While on 'auto', the set is to be started on a routine basis and automatically every week and is to operate for a minimum of 30 minutes on load before stopping.
Lifting eyes are required on all items of equipment over 25 kg in weight which may need removal.
Flexible connections shall be provided to all exhaust air fuel, and water piping to avoid fracture due to vibration and to minimise conduction of noise.
Particular Requirements and Specifications for Diesel Powered Electricity Generation Plant
Engine shall be 4 stroke, direct injection, radiator cooled and with forced lubrication from wet sump with automatic oil make-up system. Full flow oil filters shall be supplied with differential pressure alarm and gauge.
All moving live parts are to be adequately guarded to prevent injury to personnel.
Governing shall be in accordance with manufacturer's recommendations; except that manual adjustment shall be provided for± 5% rated speed and the steady load speed band shall not exceed 1% of rated speed.
Sufficient reserve shall be allowed in the lubrication system to allow 36 hours running without replenishment. Oil cooling shall be by heat exchanger. Suitable oil drainage facilities to the engineers approval shall be provided.
Thermostatically controlled jacket water heaters shall be provided. The nominal temperature setting shall be 45 Deg. C but the control should be adjustable between 30 deg. C and 50 deg. C. Vee type engines shall be provided with a heater in each bank to ensure uniform heating.
Valve seats shall be replaceable.
Five micron dual fuel filters shall be supplied in the fuel line complete with on line changeover facilities. Induction shall be via heavy-duty oil bath air filters or suitably rated disposable paper element type.
A fail-safe mechanical overspeed trip facility shall be provided, set at 115% rated speed. Suitable means shall be provided for turning the crankshaft and the associated generator by hand.
The flywheel shall be dynamically balanced and shall be capable of being rotated at 125% and 95% of rated speed during normal running.
The engine shall incorporate an adjustable isochronous electronic or hydraulic governor.
Products and Materials of Diesel Powered Electricity Generation Plant
All materials and parts comprising the units herein specified shall be new and unused, and of the highest grade in accordance with reference clauses.
The unit shall be the product of a firm regularly engaged in the manufacture of engines, and shall meet the requirements of the Specifications set forth herein. The unit shall be of a standard model in regular production at the manufacturer's place of business.
- General requirements for the equipment are: Number of Units Required - Each
- Rating: 1500 KVA
- Power Factor: 0.8
- Generator Voltage: 415V, 3 phase, 4 wire
- Frequency: 50 Hz
- Speed of rotation: Not to exceed 1500 rpm
Diesel Engine and Auxiliaries of Diesel Powered Electricity Generation Plant
The engine shall be water cooled V12N16 cylinder vee-type four-stroke cycle compression ignition diesel. It shall meet Specifications when operating on No.2 domestic burner oil. Diesel engines requiring premium fuels will not be considered. The engine shall be equipped with fuel, lube oil, and intake air filters, lube oil cooler, fuel transfer pump, fuel priming pump, gear driven water pump, fuel pressure gauge and an engine mounted instrument panel including a water temperature gauge, and a lubricating oil pressure gauge.
The engine shall be equipped with an electronic speed sensing governor capable of isochronous.
Mounting: The unit shall be mounted on a structural steel sub-base and shall be provided with suitable vibration isolators and installed inside a steel weatherproof container.
Safety devices - Safety shut-offs for high water temperature, low oil pressure, over speed, and engine over crank shall be provided.
Diesel engine is to be designed for type of load and application required. Engine and governor are to be selected to meet operating requirements and response specified.
Cylinders are to have removable liners. Wet type liners are to have witness hole between liner sealing rings of each cylinder for early detection of coolant or oil leakage. Each cylinder is to have drilled and tapped hole and valve for connections of pressure indicator.
Electronic Governor is to provide isochronous frequency regulation from no load to full rated load, paralleling and load sharing of generator sets where specified. Governor is to have zero percent (isochronous) setting and adjustable droop from zero percent to 10 percent droop. System is to include power supply unit, magnetic speed pick-up, control module and actuator using fast response DC motor drive or equally approved alternative. Governor is to be designed for fast-response and high precision of speed (frequency) control, automatic paralleling and load sharing and is to include speed adjustment to +/- 5 percent of normal, while running, and with remote control interface. Frequency deviation under 25 percent sudden load change is not to exceed 0.5 Hz, recovering to stable speed condition of +/- 0.1 Hz in 0.5 seconds.
Governor over-speed trip is to automatically close fuel pump racks in event of engine over speed. Device is to be separate and independent from governing mechanism.
Protective system is to comprise automatic engine shut- down and generator trip with visual and audible alarms in event of over-speed, low lubricating oil pressure, high cooling water temperature and over cranking.
Generator (Alternator) and Auxiliaries of Diesel Powered Electricity Generation Plant
Synchronous, low reactance, high efficiency, revolving field type, with brushless exciter and flexible coupling, sized to pick up effective load without exceeding transient and steady-state voltage deviation limits specified up to its full nominal rating and designed for the performance stipulated in the Specification. It is to be of 2 bearing construction with bearings of the sleeve or sealed ball type.
Phase leads are to be brought out fully insulated to a terminal cable box of heavy gauge sheet steel, protection IP 44. Control and protection cables are to be brought out to a separate terminal box.
Maximum voltage difference between the 3 phases at 100 % balanced load is not to With unbalanced load up to 8 percent on one phase at unity power factor and zero load on other phases, the line-to-neutral voltages are not to differ by more than 2 percent.
- Characteristics of Alternator:
- Number of phases: 3.
- Rated voltage, frequency, and net rated output: As shown on the Drawings.
- Rated power factor: 0.8.
- Winding connection: Re-connectable with ends brought out and fully insulated.
- Maximum unbalanced load current, (negative sequence component of current) with none of the phase currents exceeding rated current: 8 percent of the rated current.
- Rotor: Salient pole type, incorporating damping grid.
- Excitation: Brushless, with rotating armature rectifiers and discharge resistors.
- Voltage regulator: Automatic, with readily accessible controls for voltage level.
- Insulation: Class H for stator and class H for rotor & exciter, with class F temperature rise, unless other indicated on the Drawings.
- Enclosure: Drip proof and screen protected (IP 21 to IEC 60947-1).
- Cooling: Built-in centrifugal fans.
- Maintained short circuit: 250 percent for 2 seconds
- Over-speed: 120 percent (minimum) for 2 minutes.
- Telephone harmonic factor (THF) at no load: 3 percent max.
- Waveform distortion factor at no load: 5 percent max.
Overall voltage deviation within normal speed variations is to be within limits specified from no-load to full-load, from hot to cold and with load power factor from 0.8 lagging to unity. Regulator is to automatically reduce voltage if load exceeds capacity of generator. Voltage build-up is to be positive and rapid even when full load is suddenly applied. Line-to-line voltage waveform deviation factor is not to exceed +/- 5 percent. Total harmonic content is not to exceed 5 percent and that of one harmonic not to exceed 2 percent. Radio interference suppression is to be within the limits set by the Standards, grade (N).
Exciter: Armature is to be 3 phase, directly mounted to generator shaft and connected to generator field windings through 6 solid state, hermetically sealed, silicon rectifiers, accessible for maintenance or repair. Exciter is to have field suppression system to eliminate any source of diode failure resulting from high inductive loads and surges. Exciter field windings are to be stationary. Exciter-regulator combination is to maintain output voltage within limits specified for any load up to 110 percent generator rating and under any sudden load changes specified.
Voltage Regulator: Solid state, volts/Hz type, utilizing silicon semi-conductor devices in control and power stages, with built-in electro-magnetic interference suppression and designed for single or parallel operation. Manual adjustment to +/-5 percent of regulated voltage level is to be possible by a potentiometer at control panel. All components are to be sealed, moisture and heat resistant, with a suitable environmentally protected enclosure.
Voltage regulator is to automatically reduce voltage if load exceeds capacity of generator and is to sustain a 3 phase short circuit current at the generator terminals for the period for which the short circuit protection operates and at least for 3 seconds. Voltage regulator power is to be supported by generator voltage and current to maintain excitation field power.
2 position switch is to be provided for selection of manual or automatic mode of regulated voltage control.
Where sets operate in parallel provide cross-current compensation and necessary paralleling modules are to be provided to effect sharing of active and reactive loads equally between generators.
Instrumentation, Protection and Control Equipment of Diesel Powered Electricity Generation Plant
Measuring Instruments: Engine mounted instruments are to inciude, at least, water temperature gauge, lubricating oil temperature gauge and pressure gauge, speedometer and running time meter. It is to be possible to measure, with extra instrumentation, coolant temperature at lower end of radiator, air depression after air filter, air boost and temperature using methods recommended by manufacturer. Instrument accesses are to be normally sealed by threaded blanking caps. Speed is to be sensed via a magnetic pickup.
Generating Set Instruments, Protection And Controls: Control relays, sensing equipment, switchgear protective relays and devices and start, stop and shutdown controls are to be provided as necessary for operation specified. Generating set, instruments, protection and controls are to be mounted preferably in one control cubicle.
Instruments and controls for a non-paralleled set are to include at least the following:
- Voltmeter and 7 position selector switch.
- Ammeter and 4 position selector switch.
- Frequency meter.
- Off/tesVmanual/auto duty switch.
- Manual-start and stop push buttons.
- Kilowatt-hour meter.
- Power factor meter.
- Service-hour running counter.
- Plant exerciser.
- Potentiometer for voltage level control.
- Speed raise/lower device.
- Cool-down time setting controls.
- Illuminated indicator panel with LEOs at least for low oil pressure, high water temperature, over-speed, fail-to-start, generator overload, reverse-power, generator on load, battery low charge state
- Lamp test push-button.
- Indicating gauge and low level fuel alarm.
- Battery charger, on/off switch, pilot lights.
- D.C. ammeter.
- Alarm sounder and reset controls.
- Anti-condensation heater.
Protective gear is to ensure orderly engine stop or shutdown with reset relays, as required for safety and operational reliability, and is to include the following:
Moulded case circuit breaker (MCCB) with solid state trip unit, in accordance with section "Switchboards", (electrically operated and electrically tripped by shunt release) for over-current and external earth fault protection.
- Over-voltage protection with voltage and time lag adjustment.
- Loss-of-field/ under excitation protection.
- Phase unbalance via negative phase sequence protection.
- Restricted earth-fault protection, with current adjustable settings between 0 and 20 percent of rated current, and time adjustable settings 0 to 3 seconds.
- Reverse power relay (for sets operating in parallel).
Control and Protective Gear Cubicles: In accordance with relevant section.
Interface the control system with the BMS so that the BMS provides an automatic step loading system for sequential application of standby loads with an adjustable (0- 30 sec) time delay between each two steps based on priorities. The system is to comprise all necessary control equipment including under over/ voltage sensing relays, time delay relays, interface devices and wiring with respective circuit breakers.
Relays shall be plug-in type, front adjustable, sealed type with dust type enclosures, removable covers, test terminal blocks and plugs for testing relay without removal from case. Removal from casing is to automatically short-circuit respective current transformer secondary windings.
Instruments are to be housed in enameled metal cases for switchboard flush installation, with scales and markings protected and sealed. Indicating meters are to be minimum 76 mm square. Accuracy is to be within 2 percent unless otherwise specified. Voltmeters and ammeters are to be electronic digital type.
Current Transformers: Class 2 for measuring and protection.
KWH Meter: 3 element type for unbalanced 3-phase, 4- wire loads, fitted with 6-digit cyclometer.
Fuel Storage and Transfer of Diesel Engine and Auxiliaries of Diesel Powered Electricity Generation Plant
The entire fuel system for each engine-generator set shall conform to the requirements of BS 7698 and contain the following elements:
Install inside the container a separate self-supporting day tank with 8 hours capacity complying with BS799 part5.
- Rupture basin.
- Fuel strainer.
- 25mm solenoid valve.
- Fill pipe and Vent pipe/cap to the outside of the container.
- Drain pit cock.
- Rupture basin leak detector switch with remote signal.
- 25mm overflow to rupture basin.
- 150 mm square removable gasketed inspection plate.
- Float switch, solenoid valve and dial-type level indicator to give alarm on over-fill and low-level.
- "Press to test" switch.
- "pump running" indicator light.
- Tank drain.
- Removable top cover.
Each engine shall be provided with an integral engine driven pump. The pump shall supply fuel at a minimum rate sufficient to provide the amount of fuel required to meet the performance indicated within the parameter schedule. The fuel flow rate shall be based on meeting the load requirements and all necessary re-circulation.
A minimum of one full-flow fuel filter shall be provided for each engine. The filter shall be readily accessible and capable of being changed without disconnecting the piping or disturbing other components. The filter shall have inlet and outlet connections plainly marked.
A relief/bypass valve shall be provided to regulate pressure in the fuel supply line, return excess fuel to a return line and prevent the build-up of excessive pressure in the fuel system.
Fuel Lines: Heavy gage, black seamless steel, to ISO/R65 or equal, treated internally with corrosion resistant paint and with joints sealed with PTFE tape. Plumber's twine or gasket sealing compound are not to be used. Changes in direction and branching and jointing are to be with regular pipe fitting. Field fabricated and bent fittings are not to be used.
Valves Generally: 125 psi steam working pressure rating and 200 psi cold water non-shock pressure rating and type that can be repacked under pressure.
Pipe Hangers and Supports: Galvanized steel.
A hand pump suitable for 200 litres oil tank shall be provided with flexible suction hose for manual fuel transfer.
Ventilation and Cooling System Diesel Powered Electricity Generation Plant
The generator container shall be equipped with air intake and outlet louver panels, of sufficient free area to allow passage of combustion / cooling air within the parameters required for the selected generator set without significant pressure drop.
Both intake and outlet louver panels shall be of the inclined blade type with integral mechanical shutoff dampers, which close automatically when not energized. The dampers will open automatically when the generator is signaled to start. In addition the intake louver panel will be fitted with filters on the inside in accordance with the specification.
Engine cooling shall be by a water jacket, with water circulating pump and heavy duty tropical radiator and an engine driven pusher fan. The radiator and fan shall be sized to maintain safe operation at 50 degrees C. maximum ambient temperature. The radiator shall be equipped for a duct adapter flange.
The fan shall be rated for the specified site conditions and provide sufficient pressure to maintain the required airflow through the radiator, dueling and louvres. Provide ductwork with flexible connecting section between radiator duct flanges and exhaust louvre at facia of generator room. Exhaust louvre panels shall be demountable to enable access to generator where applicable. Ventilation louvers shall be provided as detailed in the drawings.
The cooling fluid shall incorporate sufficient corrosion inhibitor to protect the cooling system from internal corrosion. Thermostatic control shall be incorporated.
Obstructions in path of cooling air flow (openings, louvers, grilles, mesh, ducts, bends etc.) are not to reduce airflow below that needed at full rated output. Fan and radiator characteristics are to be selected accordingly. Advise if additional booster fans are required and provide necessary control gear for automatic operation.
Exhaust System of Diesel Powered Electricity Generation Plant
Exhaust system is to be complete with flanged, bolted, galvanized, seamless steel pipe sections, long sweep elbows, flexible expansion sections, clean-outs, industrial 18dBA attenuation silencer, wall thimbles and supporting steelwork. Silencer is to be independently supported. Indoor hot exhaust parts are to be insulated with mineral wool/rock wool material, not less than 50 mm thick, retained by wire ties and cladded with sheet metal aluminum (22 - SWG) covers to protect insulation.
Exhaust system is to be designed to reduce back-pressure to below maximum specified by the manufacturer, in relation to exhaust pipe length shown on the Drawings. The exhaust system shall be manufactured in heavy quality steel tubing fitted with suitable robust gas-tight flexible sections close to the engine to allow engine movement and to reduce the transmission of engine vibrations to the remainder of the exhaust system and the surroundings. Bends shall have a minimum radius of three times the diameter of the tube. As far as possible, flexible sections shall be vertical, free from bends and have sufficient length or slack to allow free movement without damage.
Silencers shall be of the heavy duty baffie and absorption, residential type, so designed and installed as to reduce noise to the specified minimum level. The whole exhaust system including pipe-work and silencer shall be designed so that the generator set can deliver its design output at site conditions.
The silencers and exhaust pipe-work shall be properly and adequately supported clear of fuel and feed pipes and shall be provided with suitable insulation to protect personnel, plant and buildings from excessive heat. Design of exhaust system shall be suitable for site conditions and routing, where shown on layout.
The pipework shall drain away from the exhaust manifold and drain pipes shall be fitted in the low points of the system to avoid accumulation of condensate.
The system shall be so constructed as to enable it to be readily dismantled for maintenance. Provision shall be made to prevent rain water entering the exhaust pipe at its outlet to the atmosphere.
All exhaust connections shall be made as specified.
Include all necessary brackets, supports, insulation and protection, together with all fixing bolts. Bolts, washers and nuts shall be greased with graphite grease or other suitable heat resisting lubricant during assembly.
The finish of all exhaust silencers exposed to the open air shall be sprayed metallic aluminium by special process complying with the recognised industry practices.
Lubrication System in Diesel Powered Electricity Generation Plant
The engine lubricating system shall conform to BS7698 and operate under a predetermined and constant pressure.
The primary lubricating oil pump shall be an engine driven, positive displacement pump. Provide a sump pump, relief valves and by-pass valves as required for proper operation.
One full flow strainer and one full flow strainer and duplex filter shall be provided in the lube oil line on the discharge side of the lube oil pumps. The strainer shall be of the metal edge or screen type with a maximum spacing of 0.007 inch (80 mesh).
The filter shall be of the multiple cleaning and replaceable element type and the filter case shall be compatible with the filter element. A pressure relief valve shall be provided to relieve if it becomes clogged. An alarm condition shall be annunciated when the relief valve is in the open position. The strainer and filter shall be mounted in accessible locations without disconnecting the piping or other engine equipment when changing the strainer and filter element. Indicating pressure gauges shall be provided to measure the pressure drop across the strainer and filter.
Safety System in Diesel Powered Electricity Generation Plant
The generator set shall be equipped with automatic safety devices which shut down the generator set and open the generator circuit breaker in the event of low lubricating oil pressure, high coolant temperature, engine over speed, high lubricating oil temperature, over load and as specified elsewhere. The stop switch on the engine instrument board may be connected in the circuit if so recommended by the manufacturer.
The safety system shall be equipped with visual and audible devices that become operational before engine shutdown.
Lube oil pressure and cooling water temperature and pre-alarms to be inter-connected to the Building Management System.
Simultaneous activation of the audible signal, activation of the visual signal, stopping the engine, and opening the generator field and main circuit breakers shall be accomplished.
For startup of the engine-generator set, time-delay devices shall be installed bypassing the low lubricating oil pressure alarm during cranking, and the coolant-fluid outlet temperature alarm. The lube-oil time-delay device shall return its alarm to normal status after the engine starts. The coolant time-delay device shall return its alarm to normal status 5 minutes after the engine starts.
Provide remote monitoring/controls via a suitable LONWORKS compatible BMS interface.
Starting System of Diesel Powered Electricity Generation Plant
Engine starting is to be manual by push-button or automatic through control system at control panel. Electric starting shall comprise of 24 V equipment including starter motor, alternator and rectifier, lead acid batteries of ample capacity and mains powered constant voltage charging equipment and all connecting wiring.
Cranking motor and battery are to be rated for cranking the engine when cold and at lowest temperature recorded. Starting pinion is to automatically disengage when engine fires.
Batteries are to be Lead-acid, sealed-in-plastic type, complete with battery rack and inter cell connectors. Battery is to have sufficient capacity to provide and capable of withstanding five 20 second starts in succession in any four hour period, without any derating.
The Battery Charger shall be 25 percent over-rated, solid state, full-wave rectifier type, adequate to fully recharge depleted battery in not more than 8 hours and to automatically control rate of charge (providing a high-charge rate to a depleted battery and reducing to a trickle-charge rate when battery is fully charged). Ammeter is to be provided to indicate charging rate, which is to be adjustable.
The batteries shall be used to supply auxiliary relays as required whose operation must not be affected whilst supplying starting current. Auxiliary circuits are to be protected by fuses.
Control Operation in Diesel Powered Electricity Generation Plant
The manufacturer shall provide the following switch selectable operational modes on the diesel electric generator control system.
- Manual Control (Manual start and stop).
- Semi-Automatic Control (Auto-start manual return).
- Full-Auto control (Auto-start with auto stop when commercial supply returns).
For remote monitoring/controls, comply with the specified requirements.
In the automatic mode, main failure shall cause a changeover relay to de-energise. This relay shall have an adjustable 0-10 seconds delay before contacts re-set when it is de-energised so that if power is restored within that period no changeover shall take place. If the power is not restored, the changeover relay contacts shall re-set and operate as follows:
- The mains contactor control circuit shall be opened. This contactor will already have opened owing to loss of supply.
- The engine run relay shall be energised and the standby set run up.
- The standby contactor control circuit shall be prepared and complete when the generator voltage and frequency monitors show that the set is up to speed, and the contactor shall close. The generator is required to take over full load within 10 seconds of start up.
- When mains power is again available it shall be detected by a reset timer with an adjustable time delay of 0-30 minutes before operation when energised. When the timer operates it shall energise the changeover relay. Energizing the changeover relay shall:
- Open the standby contactor control circuit, dropping out the contactor.
- Close the mains contactor control circuit so that the contactor closes.
- De-energise the engine run relay.
The relay shall have a time delay adjustable up to 15 minutes before the contacts re-set to allow the engine to continue to run on no load before shutting down.
If the engine fails to start after 4 adjustable cranking attempts (factory set at 10 seconds on and 10 seconds off, adjustable from 5 to 30 seconds) or if any protective device should operate while the engine is running, the engine shall be disconnected from the service and immediately stopped. The engine control logic shall lock the failed set out of service and requires a manual reset. The engine control logic shall include a provision for conversion to single cycle cranking, adjustable from 35 to 210 seconds.
Coordinate with the requirements of enclosed transfer switches and provide controls accordingly.
- All cabling and small wiring shall be securely fixed with suitable cleats in systematic runs; small wiring shall be multi-strand copper not smaller than 1.0 sq.mm flexible cord.
- Power and small wiring cables interconnecting major components shall be heat and oil resisting.
- All cabling and small wiring shall be coded and terminated with lugs or letters of the terminals to which they are connected. Terminals shall be numbered or lettered, easily accessible and fitted with individual insulating barriers or adequately spaced.
- Barriers shall be fitted to separate control terminals from power wiring terminals.
The generator neutral point and all metalwork housing electrical equipment shall be connected to the building earthing system as specified.
Switching and control devices shall be solid state where possible. Electro-mechanical relays shall be of robust and rugged construction with rolling or wiping contacts. They shall be mounted on individual sub-bases and wired so that easy access is obtained to soldered connections. The thermal type of time delay relay will not be accepted.
A spare fuse cartridge for each pole shall be mounted inside each equipment.
Rectifiers and capacitors shall be suitable for any transient voltages likely to be encountered during the operation of the equipment and for the internal operating temperature of the enclosures at the specified maximum external ambient temperature.
Suitably rated heaters for operation on the appropriate voltage shall be provided for every alternator, motor and electrical panel. A separate terminal block shall be provided for the heater supply in each relevant panel.
Labeling and Safety of Diesel Powered Electricity Generation Plant
Each major component of the unit shall have the manufacturer's name, address, style, type or catalog number on a place securely attached to the component of the units.
The function or duty of each meter. instrument, indicator, switch, or push buttons or other device for external control, shall be clearly defined with labels in accordance with the specifications.
An instruction notice and first air chart for the proper and safe working of the plant shall be fixed in a position close to where the operation is carried out.
The engine/generator set shall have a notice fixed in a conspicuous position, with titles at least 25 mm high and remainder 12 mm high, both in Arabic and English and in red color, stating:-
DANGER- KEEP CLEAR
THIS SET IS REMOTELY/AUTOMATICALLY CONTROLLED AND MAY START AT ANY TIME. WRITTEN AUTHORITY MUST BE OBTAINED AND APPROPRIATE SAFETY PRECAUTIONS TAKEN BEFORE ANY WORK IS UNDERTAKEN ON THE SET OR ASSOCIATED CONTROL EQUIPMENT.
Exposed parts that are subject to high operating temperatures or are energised electrically and moving parts which are of such nature or so located as to be a hazard to operating personnel, shall be insulated, fully enclosed, or guarded. Guarding shail be arranged in a manner that will not impair the proper function of these parts.
Painting shall be in accordance with the appropriate specification requirements.
Inspection and Testing of Diesel Powered Electricity Generation Plant
Work Tests: Provide the manufacturer's test in accordance with BS7698 on the completely assembled unit in the manufacturer's plant. Submit the results with Shop Drawings prior to installation.
Field Tests: Provide a factory-trained representative to supervise erection and testing of the emergency engine driven generator system. Submit the results of the -following tests in report form:
Sequence of Testing: Check all engine and driven unit mounting bolts. Check alignment of engine and generator by dial indication. Check generator rotor air- gap.
Test generator and exciter insulation resistance with a megger: Take generator readings at circuit breaker, to include generator leads to switchboard.
Perform engine manufacturer's recommended prestarting checks.
Start engine and make engine manufacturer's "after-starting" checks during a reasonable run-in warm-up period.
Operate generator set for three hours at 75 percent of rated load using a load bank supplied by the generator manufacturer specifically for the purpose.
Follow above run immediately with three hours at 100 percent of rated load. Provide a load bank for utilization during the testing phase.
Checks to be Made During Testing. During the tests, all operations of which the controls are capable shall be performed to assure that all controls are functioning in a satisfactory manner.
At several points during the tests, each instrument shall be observed to ensure that all instruments and gauges are functioning properly.
During the tests, all auxiliary and accessory equipment, all valves, including pilot valves, and the injection pumps shall be checked to ensure proper operation.
Temperature readings of the manifold shall be taken and compared with those obtained during the manufacturers tests.
Verify the equipment has been installed and field dimensions are in accordance with the approved installation drawings.
Verify that all required service connections have been made utilities in accordance with the approved installation drawings and are ready for use.
During test, record the following at 30 minutes intervals and after each load step change:
- 3 phase/single phase Voltages.
- Coolant/lubricant temperatures.
- Internal and external temperature.
- Oil pressure.
Test alarm and shut down circuits by simulating conditions.
Test system in case of automatic mode as described in this specification.
Demonstrate adequacy of engine-generator unit to operate as specified in all aspects. Any failure to demonstrate adequacy in any respect shall be corrected to the satisfaction of the Engineer.
Training for Operation and Maintenance of Diesel Powered Electricity Generation Plant
Provide instruction and training to the Owner's staff for the operation and maintenance of the equipment. Provide a minimum of 18 hours training to be divided between classroom and hands-on training as required by the Owner.
Operation and Maintenance Programme in Diesel Powered Electricity Generation Plant
Submit shop drawings showing plan and elevation views with overall and interconnection point dimensions, fuel consumption rate curves at various loads, ventilation and combustion air requirements, and electrical diagrams including schematic and interconnection diagrams.
Submit product data showing dimensions, weights, ratings interconnection points, and internal wiring diagrams for engine, generator, control panel, battery, battery rack, battery charger, exhaust silencer, vibration isolators, fuel tank, sound attenuation, sand filter, radiator, and remote annunciator.
Submit operation and maintenance data, include instructions for normal operation, routine maintenance requirements, service manuals for engine and fuel tank, oil sampling and analysis for engine wear, and emergency maintenance procedures.
Spare parts and Tools for Diesel Powered Electricity Generation Plant
Furnish the spare parts normally provided with engine generator set for a period of two years as recommended by the manufacturer, plus the following:
- One set of fuel injectors.
- Two filters for all services (fuel, oil and air).
- One fuel injection pump complete.
- Three fuses for each rating.
Spare parts shall be packed in suitable containers or boxes bearing labels clearly designating the contents and the piece of equipment for which they are intended.
The manufacturer's local agent shall at all times have an adequate stock of consumables (eg: lubrication oil, oil filters, air filters) in his spare parts stores and ensure the availability of all spare parts for the proposed diesel generators for a minimum period of 5 years after the date of practical completion. The Engineer reserves the right to inspect the tenderer's spare parts stores to ascertain the capability of the organisation. At any given time 80% parts should be available in stock and tenderer should guarantee balance can be arranged in max. four working days.
Quality Control of Diesel Powered Electricity Generation Plant
Handle, store and install all equipment and components of the standby generator system in accordance with the manufacturer's recommendations and BS 7698. Ensure set is positioned to allow on-site maintenance and repairs, including barring facility where indicated. Provide access for removal of pistons and connecting rods.
Inspect all equipment and componef)ts on delivery, before fixing and after installation and reject and replace any, which are defective.
Carry out factory and site tests as specified.
Equipment furnished under this section shall be guaranteed against defective parts or workmanship for a period of 12 months, from the date of acceptance by the Engineer, under proper operation as per manufacturer's recommendations.