This article covers the manufacture, supply, installation, testing and commissioning of 415 volts, 3 ph, 4 wire, Diesel Alternator Set (Diesel Genset). The set shall be mounted on common base frame and complete in all respects including the auxiliary equipment such as battery auxiliary, lube oil pumps, filters, oil storage tank, centrifuge, etc. including piping required for interconnection between the set and the auxiliaries which are mounted separately.
Contractor shall specify in detail all equipment offered including auxiliaries. Rating of the Diesel alternator set shall be based on the operation of the set when equipped with all necessary operating accessories. The DG set to achieve full speed in 8 secs. or less. Rating shall correspond to 40 degree C ambient air temperature.
Diesel Engine for Emergency Power Genset
1. Construction of Diesel Engine
The Diesel Engine shall be operating on high speed diesel oil. The engine shall preferably be of 2 stroke design. Engine should be of robust construction suitable for continuous operation. Bearing housings shall be sealed against ingress of dirt and loss of lubrication.
2. Dynamic Characteristic
An analysis be made of engine, coupling (s) and driver/drivers to ensure the complete installation of starts, operates and stops free from vibration and oscillation in excess of normal industrial standard.
- Air - Oil wetted air filters for direct mounting on the engine air manifold or equivalent.
- Fuel-Duplex fuel oil filters with changeover valve.
- Lubricating Oil-Duplex filters with changeover valve.
Flywheel shall be designed and manufactured to meet cyclic variation levels as specified in IS 649-1958.
Governor should be centrifuged hydraulic servo assisted. Governor should be a self contained unit complete with its own pump and oil supply. Governor should maintain the speed within 1.0 cycle to minimum of 50 cycles from no load, including no load, shall remain within steady state band width ± 0.25% of rated frequency. The governor shall not permit frequency modulation to exceed one cycle per second. Oil generator to have necessary reserve of oil to permit auto start on AMF system.
6. Fuel system
Fuel system shall have pump feed to engine driven fuel pump and replaceable element fuel filter conveniently located for servicing. Contractor shall provide fuel oil day tank of 8 hours capacity with supports, level gauge and connecting tubing fuel oil pump suction header.
7. Pressure oil system
All lubricating points of the engine shall be connected to pressure oil system. The system shall be so designed that when the engine starts after prolonged shutdown, lubrication failure does not occur. Oil drippings from lubricating points shall have connection to the oil sump and recirculated. Full flow strainer shall be provided at oil pump suction. Oil sumps shall be fitted with level gauges for visual observation.
Note: Ambient temperature can be as low as 2 degree C in winter and hence if necessary suitable oil heaters to be provided for quick start upto full speed within 8/10 secs.
8. Cooling system
A closed independent self contained cooling system shall be provided for the engine cooling comprising of radiator, engine, driven fan, thermostatic bypass valve. Engine driven water circulating pump shall be used for the system.
Alternatively, for higher ratings, extra price to be indicated for separate water cooled heat exchanger with cooling water inlet at 35 degree C and outlet 40 degree C maximum with necessary pump for water circulation.
9. Starting System
Engine shall be started by 24 V, DC starting motor supplied to axial type starter motor engaging on the toothed ring of the flywheel.
Special silencers for reducing the noise level to around 75 dB measured 1 m from exhaust pipe shall be provided. The silencer shall preferably be of the hospital type, with flexible connections, etc.
The engine shall be mounted on common base plate with alternator, properly aligned and assembled. The composite set shall be mounted on anti vibration mountings.
12. Instrumentation and controls
Instrumentation: Instrumentation shall be housed in a panel mounted at the free end of the engine.
Following instruments shall be provided:
- Cooling water temperature indicator Degree C.
- Lubricating oil temperature indicator Degree C
- Lubricating oil pressure gauge psig.
- Engine rpm indicator with running hour meter.
- Engine over speed trip and indicator together with alarm and light.
- Cooling water temperature high (alarm & indication).
- Low lube oil pressure (alarm and indication).
Following protective and devices and equipment shall be provided for the engine protection.
Controls: Mechanical over speed governor and shut down device. Visual and audible alarms and associated devices shall be provided for the following conditions. Shut down solenoids and relays shall also be provided to stop the engine in the event of any of these faults.
- Low lubricating oil pressure.
- Excessive cooling water temperature.
- Excessive lubricating oil temperature.
- Over speed of the engine.
Alternator for Emergency Power Genset
The specification of the alternator are as per Bill of Quantities. Alternator shall be in accordance with the following standards as far as possible.
- BS 2613: The electrical performance for Rotating Electrical machines.
- BS 269: Rule for method of declaring efficiency of electrical machine.
- BS 1231 & 2490: Dimensions of 3 phase electric motors.
1. Alternator Type
The machine will be of rotating field stationery armature type brushless self excited. The excitation supply shall be obtained from a shaft mounted excitor, and AC generator supplying the field winding through shaft mounted rectifier from the alternator terminals.
2. Performance requirement for the Alternator
The voltage regulation from no load to full load shall be within ± 1.5% of rated voltage. Steady state frequency variation shall not exceed one cycle per second. For any addition of load upto and including 90% of rated load, the voltage drop shall not exceed 20% of rated voltage. The voltage shall recover to and remain within the steady band in not more than 1.5 seconds. The frequency regulation from no load to rated load shall be in accordance with that defined by the engine governor performance. For any addition of load upto 90% of rated load, the frequency shall recover to the steady state frequency and within 5 secs.
3. Automatic Voltage Regulation
±1% full load imposed or removed and recovery to rated voltage within 1 second.
4. Alternator Enclosure
Alternator stator enclosure shall preferably be totally enclosed fan cooled (IP 44). However, if this is not feasible, a screen protected drip proof (SPDP) enclosure may be acceptable, provided special treatment is given to the windings, such as double impregnation of winding. The stator frame shall be either of cast iron or of fabricated steel constructions.
5. Earth Terminal
Two number M 12 earth terminals to be provided on opposing sides of the alternator, complete with all hardware, including plain and spring washers for secure, vibration proof connections. All hardware to be galvanized or plated and passivated.
6. Alternator Windings
The alternator winding shall be treated to render the non hygroscopic and resistant to acidic/ alkaline vapours. Class ‘B’ insulation shall be used for stator and rotor windings. 2 nos. of resistance temperature detected per phase shall be embedded in alternator stator where hot spots are likely to occur.
7. Space Heaters for Alternator
Anti condensation space heaters shall be provided to maintain winding temperature 5 degree C above ambient temperature. The heaters shall be suitable for operation on 240 V, 1 phase, 50 Hz, Ac supply. Heaters terminals shall be brought to separate terminal box. A caution name plate ‘CAUTION LIVE TERMINALS - ISOLATE SUPPLY ELSEWHERE BEFORE DISCONNECTIONG’ shall be affixed on the terminal box. The space heaters shall be of metal encased and low surface temperature type.
Electric Control Panel for Emergency Power Genset
Electric control panel shall be sheet steel clad, totally enclosed, dust damp vermin proof, free standing floor mounted, front of broad operated. Indicating instruments, relays, annunciators, indicating lamps, etc. shall be flush mounted on the front. Removable undrilled gland plate of suitable size shall be provided at the bottom of the control panel for terminating control cables.
Anti condensation space heaters shall be provided inside the control panel. Heaters shall be provided with separate control switch and protective fuses. The control panel shall be painted with approved shade.
2. Instrumentation and Control
Following instruments, motors, relays and equipment shall be provided in the control panel:
- 0-500 V, Voltmeter with 6 position selector switch with protective fuses (for alternator potential) size 144 mm square.
- Ammeter with 4 position selector switch (for alternator load) size 144 mm square.
- Frequency meter size 144 mm square.
- Power factor meter, 0.5 lag, unity, 0.5 lead, 3 phase 4 wire.
- KWH meter, 3 phase 4 wire.
- KW meter, 3 phase, 4 wire.
- Voltmeter and supervisory lamp for 24 V DC supply supervision.
- Emergency stop push button for alternator contactor/ circuit breaker and engine.
- Auto/ Manual/ Test selector switch.
- Automatic voltage regulator and auto/ manual selector switch, with current compensating transformer.
- Protective relays for protection against earth fault/ short circuit, overloads, motor action, under frequency, field failure, under voltage, over voltage, etc. shall be provided as called upon vide Bill of Quantities.
- All relays contactors and any other equipment or devices required for the desired operation.
All potential circuits shall be provided with link type HRC fuses similar to English Electric make, type NS.
3. Power isolation
Aadequate rating Moulded case Circuit Breaker/ Air Circuit Breaker with thermomagnetic releases shall be provided as called upon vide Bill of Quantities.
The AMF set is required to provide electric power to the essential loads in the event of failure of normal power supply. when normal power fails, the set shall be started manually to feed essential loads.
Lead Acid 24 V DC Battery for Emergency Power Genset
The battery cells and the charging equipment will be separate units. The battery shall be in accordance with IS 1652. Specifications for stationary cells and batteries lead acid type.
1. Battery Capacity
The battery capacity shall be decided by contractor to suit the required duty. The discharges rate shall take into account the maximum load imposed at starting of engine, together with steady load such as indicating lamps, relays, etc.
3. Accessories and Tools for Battery
The following accessories and tools are required for battery and shall be supplied by the contractor:
- Hydrometer, syringe type suitable for specific gravity reading of the electrolyte.
- Thermometer with specific gravity correction scale.
- Acid level indicator.
- Center zero 3-0-3 voltmeter.
- Any other accessories considered necessary/ desirable by the contractor.
Battery Charger for Emergency Power Genset
The battery charging equipments (transformer unit) are provided to charge the 24 V, battery required for diesel engine starting. The battery charging equipment shall be 30 A rated or higher and automatic type.
1. Battery Charger Construction
The battery charging equipments shall be housed in sheet steel enclosure. If a separate unit is provided then it should be free standing, floor mounting, totally enclosed, dust, damp, vermin protected suitable for indoor location.
2. Operation of Battery Charger
1. The battery will normally be in parallel with a constant voltage float (trickle) charges of adequate capacity to meet the continuous load and to keep battery in fully charged conditions under all the conditions or system variations.
2. A boost charger shall be provided for initial charging and recharging the batteries when they are in ‘run down’ condition. A selector switch for selecting ‘float charge’ or ‘boost charge’ shall also be provided on panel.
3. the charger supply will be available from nearest convenient power outlet.
3. Accessories Along with Battery Charger
The following instruments shall be mounted on the charger panel:
- Voltmeter with protective HRC fuses.
- Selector switch (float/ medium/ full charge/ off).
- Indicating lamps with ballast resistors and protective HRC fuses. For AC supply ‘ON’ and DG supply ‘ON’.
4. Internal Wiring of the Charger
All internal wiring of charger unit shall be carried out with 660 V grade, PVC insulated, copper conductor cables (preferably with stranded conductors). An undrilled gland plate shall be provided for termination of outgoing cables. Both the ends of cables shall be provided with identification ferrules.
5. Earthing for Battery Charger
All metallic non current carrying parts of equipment and the enclosure shall be bonded together and to the two earthing terminals provided on the enclosure.
Drawings and Information for Emergency Power Genset
Contractor shall furnish all the information during tender stage itself including the following drawings:
- General arrangement drawing of diesel alternator set including principal and auxiliary equipment accessories, battery, auto changeover panel, piping, foundation etc.
- Schematic control wiring diagrams and block schematic diagrams showing interconnections between various equipment.
- Installation, operation and maintenance manuals for engine, alternator, changeover panel, battery and battery charger.
- Technical literature for all equipment.
Engine and auxiliaries:
- Make, type and continuous ratings.
- Bore, stroke and number of cylinders.
- Efficiency curve at various loads.
- Speed load characteristics.
- Lubrication system.
- Weight of complete set, erection and maintenance and Headroom clearance for maintenance.
- Make and type.
- Enclosure and frame size.
- Continuous rated output and synchronous speed.
- Power factor.
- Insulation class.
- Temperature rise above 40 degree C ambient.
- Rated voltage.
- Full load current at 0.8 pf.
- Lubrication system.
Battery and Battery Charger:
- Make and type of battery.
- Detailed wiring diagram for battery charger and write up on operation
- Ampere Hour ratings of battery (10 hr rate) and charge and discharge characteristic of battery.
Test and Test Certificates of Emergency Power Genset
Contractor shall carry out the routine tests on engine as per BS 649 and for alternator as per BS 2613. However, following specific tests shall be carried out for the test.
- Operation Test.
- Check the automatic starting and starting time of set, to come on load.
- Test for automatic voltage regulation.
Contractor shall submit complete data of all equipment and test certificates for all tests (routine and specific carried out for the test).
Installation, Testing and Commissioning of Emergency Power Genset
Diesel generator set shall be installed on the foundation provided. All electrical, mechanical piping connections be carried out by the contractor to the full satisfaction and as per manufacturer’s drawing.
After installation of set and its accessories, auxiliaries, no load and load tests shall be carried out. Operation of all meters, relays, protective devices, interlocks, etc. shall be checked in detail.
HV tests, Meggar tests and earth continuity tests shall be carried out.