This article is for the design, materials, manufacture, testing, and commissioning of packaged stand-by diesel engine generators intended for permanent installation in industrial plants. Main keywords for this article are Diesel Generator Working Principle, Diesel Generator Parts and Functions, Diesel Generator Efficiency, Diesel Generator PDF, Diesel Generator Tests.
Diesel Generator References
American National Standards Institute (ANSI)
C50.10 Rotating Electrical Machinery – Synchronous Machines
C50.12 Salient Pole 50 Hz and 60 Hz Synchronous Generators and Generators/Motors for Hydraulic Turbine Applications Rated 5 MVA and above
Institute of Electrical and Electronics Engineers (IEEE)
115 Guide: Test Procedures for Synchronous Machines Part I
National Electrical Manufacturers Association (NEMA)
MG 1 Motors and Generators
National Fire Protection Association (NFPA)
70 National Electrical Code
110 Standard for Emergency and Standby Power Systems (National Fire Codes, vol. 5)
Diesel Generator Working Principle
- The diesel engine generator (DEG) system shall provide the source of standby power for critical electrical loads when normal electrical power is not available.
- The generator set shall be supplied as a complete package comprising diesel engine, generator, controls, cooling system, starting system, and diesel day tank. The generator set package shall conform to NFPA 70 Article 702, NFPA 110.
- The generator set shall be supplied in accordance with the electrical one line diagram which shall indicate the generator kW, output voltage, and the protective relays required for generator protection. ANSI relay designations shall be utilized.
- Engine-generator unit and accessories shall be designed for a 20-year life expectancy, and shall be capable of operating at 105 percent of rated speed without overstressing any part of the engine, generator or accessories.
- Engine-generator unit shall be capable of continuous operation at all loads up to and including rated load at the specified operating conditions and at 110 percent of rated load for two (2) hours out of every 24 hours.
- Engine-generator shall start, reach full speed and be ready to pick up load in no more than 15 seconds. System load shall be picked up immediately after engine is stable.
- Engine-generator shall be capable of unattended operation at rated full load or any partial load, while maintaining rated voltage and frequency for a period not exceeding two (2) days. Engine-generator shall be capable of being started and exercised under partial or full load for a period of at least two (2) hours per week.
- DEG system shall be capable of accepting 85 percent of rated load or shedding 100 percent load without exceeding an 8 percent frequency and 10 percent voltage variation at the generator terminals, and shall be capable of starting the largest motor connected as essential load without exceeding a 2 percent frequency droop and 15 percent voltage drop. DEG shall be capable of accepting 50 percent of rated load without exceeding a 5 percent frequency droop.
- Engine-generator set shall be able to start under black-start conditions, that is, without power for the auxiliary devices on the generator set, using only generator set battery, or the air contained in the starting air tanks and fuel supplied from the day tanks.
- A constant speed governor shall be supplied for the generator set that has the capability for load sensing and will maintain isosynchronous speed of the engine at ± 0.25 percent of steady state speed.
Diesel Generator Efficiency
- Generator shall be capable of continuous duty service and shall operate successfully at rated kVA, frequency, and power factor at any voltage not more than 5 percent above or below rated voltage.
- Generator shall be capable of withstanding 20 percent overspeed without mechanical damage.
- Generator rotation shall be dictated by the driver rotation. Phase sequence shall be 1, 2, 3, with counterclockwise phase rotation.
- Generator shall be designed with limiting values for subtransient reactance and shortcircuit ratio.
- Generator armature and field winding short-time thermal requirements shall be as specified in ANSI C50.12.
- The generator rotor short-time thermal requirements for unbalanced faults shall be as specified in ANSI C50.12.
- In addition to the mechanical requirements for short circuits specified in ANSI C50.12, the generator, voltage regulator, and exciter system shall be capable of sustaining at
least 300 percent rated generator current for 10 seconds, if a 3-phase, symmetrical short circuit occurs at the generator terminals. - The requirements for continuous current unbalance of the generator shall be as specified in ANSI C50.12.
- Generator shall have Class F insulation with the temperature rise limited to Class B (80 °C rise by winding resistance temperature detector (RTD) in a 50 °C ambient.
- Generator shall be capable of continuous operation at the limiting observable temperature rise, as specified in ANSI C50.12. Generator shall conform to the design requirements specified in NEMA MG 1.
- The stator frame shall have easily removable end enclosures and associated ventilating system. The frame shall be of sufficient strength to support the armature laminations and coils.
Main keywords for this article are Diesel Generator Working Principle, Diesel Generator Parts and Functions, Diesel Generator Efficiency, Diesel Generator PDF, Diesel Generator Tests.
- Generator windings shall be suitable for wye or delta connection with both ends of each winding brought out to terminals, in an accessible location. Either end of the windings shall be suitable for phase terminals; leads shall be separated and adequately braced.
- An oversized terminal box shall be provided to house the neutral ground current transformer (CT).
- Machines rated 1000 kW and above shall have the stator windings equipped with 12, 100: platinum RTD’s, four (4) per phase, wired to a terminal strip in a NEMA 4X
stainless steel or cast iron terminal box for continuation wiring by. The RTDs shall be 3-wire and shall be located in each phase where the maximum temperature
may be detected. Six (6) of the RTD’s shall be used for local temperature indication and six (6) RTD’s shall be used for protective relaying. - For machines rated 1500 kW and above, the lower section of each bearing shall be provided with two (2), 100:, platinum RTD’s. The RTD’s shall be located within 6 mm of the bearing surface. The RTD’s shall be wired to a separate terminal box.
- The armature laminations shall be constructed of high-grade steel, suitably secured to the stator frame. Spacers shall be provided at intervals along the length of the core to
form radial ventilating ducts. The laminations and spacers shall be securely clamped together to minimize undue vibration and noise. - Main armature coils shall be form-wound and exciter armature coil shall be random wound.
- Generator rotor shall be made of steel. Radial slots shall be machined in the rotor body to receive the field coils.
- Generator shaft shall be accurately finished throughout its entire length, and shall be grounded at bearing and sealing surfaces and adjacent to the bearing surfaces, to permit vibration measurements.
- Generator rotor shall be statically and dynamically balanced. During the shop test of the assembled generator while operating at rated speed, the double amplitude of vibration, including mechanical runout in any plane measured on the shaft adjacent and relative to each radial bearing, shall not exceed 38 Pm (11/2 mils). A 6 Pm (1/4 mil) maximum shaft electrical runout, as measured on test, may be deducted from measured vibration. Vibration readings taken on the housings shall not be acceptable.
At the overspeed condition, the double amplitude of vibration shall not exceed 100 Pm (4 mills). - Bearings shall be insulated to prevent shaft current circulation.
- Neutral CT shall be provided for ground fault protection or ground differential protection.
Generators shall have jacking bolts, or facilities to lift the generator with the aid of mechanical jacking device, to facilitate alignment of the generator with prime mover.
Generator Controls / Diesel Generator Parts and Functions
- Exciter. The exciter shall be of the static, rotating brushless, or comparable selfventilating type, mounted on or coupled to the main generator shaft external to the bearing opposite the drive end.
- Voltage Regulator. The voltage regulator shall be a completely solid-state voltage regulator for control of the generator voltage by control of the exciter field. No vacuum tubes or electromechanical relays shall be used in the voltage regulator.
- Space Heater. Electric space heaters shall be provided in the generator, exciter housing and control panel to prevent condensation when not in service. Space heaters shall be rated for 240 V AC, single phase and shall operate on 120 V AC, single phase.
- Resistive Load Bank. An adequately sized resistive load bank shall be supplied for purposes of testing and exercising the generator set. The load bank shall be compact, portable and fully self-contained, with all metering, controls and test instrumentation.
- Exciter shall be sized to provide 20 percent capacity in excess of that required to supply the field excitation of the generator when the generator is operated at 5 percent above normal rated kVA output, at rated power factor, and at normal voltage without exceeding rated temperature rise.
- The main exciter response ratio shall be minimum of 0.5.
- The exciter current rating shall be guaranteed to be at least equal to the actual excitation required by the generator at rated power factor and load when operating at 5 percent above rated voltage.
- For static excitation systems, a comparable auxiliary pilot excitation system shall be furnished to facilitate generator operation and startup.
- The rotating brushless exciter, if mounted or coupled to the generator shaft, shall be capable of withstanding 20 percent overspeed without mechanical damage.
- Generators supplied with rotating brushless excitation shall be furnished with an auxiliary pilot exciter permanent magnet generator (PMG) type, shaft mounted, outboard of the brushless main exciter.
- Exciters of the rotating brushless type shall be ventilated by means of cooling air received from the main generator, circulated through the exciter, and returned to the main generator.
- The voltage regulator system shall include voltage transformers and voltages adjusting rheostat, as required for proper operation.
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Diesel Generator Enclosure
Self-contained enclosure shall be provided for the diesel generator set.The enclosure shall be manufactured such that all part are accessible for inspection and minor maintenance without removal of the enclosure or enclosure roof. It shall include the following features:
a. The enclosure and all other items shall be designed and built by the supplier as an integral part of the entire diesel generator set, and shall perform without overheating in the environment specified.
b. It shall be constructed of minimum 14-gauge sheet metal, suitably reinforced to reduce vibration in the operating mode.
c. A minimum of four doors are required. The doors shall be hinged so that they can be opened to provide complete access to the equipment inside the enclosure without removing the doors.
d. The side and rear panels shall be completely and simply removable to permit major service access.
e. Doors shall be lockable.
f. All exterior steel surfaces, including those in contact with the foundation, shall be epoxy-or epoxy-mastic-coated as a minimum. Interior surfaces shall have the vendor’s standard finish. All fasteners shall be corrosion resistant.
g. Batteries shall fit inside the enclosure and alongside the engine (batteries under the generator are not acceptable).
h. The unit shall have coolant and oil drains piped to the outside edge of the skid in an accessible location. Each drain line shall have a valve located near the fluid source.
i. Air Intake louvers shall be sized to provide sufficient airflow for engine combustion, engine cooling and generator cooling. The louvers shall open automatically when the engine receives the start signal and close when the engine stops. They shall also allow manual over-ride.
j. The air intake and exhaust outlet shall be configured such that exhaust gas recirculation to the air intake will not occur under any wind direction.
k. 120 VAC lights, light switch, 120 V receptacles, and an associated load panel shall provided. The 120 V source will be provided by others.
l. Diesel generator set shall not generate noise in access of 85dba at a distance of 1 meter. If the sound pressure level will exceed 85 dba, the vendor shall notify the purchaser and additional cost for modification to ensure the sound pressure does not exceed 90dba at 1 meter. dba.
Transport units heavier than 25 kg shall have eyebolts, lugs, or extension pieces clearly identifiable to be used for hoisting.
A separate junction box or boxes shall be provided on the generator enclosure for connections to space heaters, temperature detectors, thermocouples, and humidity detector, if any.
Diesel Generator Control Panel
Generator control system shall be contained in a single control panel. Instrumentation shall be supplied by generator manufacturer as outlined in this section. Any instruments to be furnished by the generator manufacturer beyond normal generator control requirements. The control panel shall include:
a. Voltmeter (2 percent accuracy) and 3 phase switch
b. Ammeter (2 percent accuracy) and 3 phase switch
c. Frequency meter
d. Voltage Adjusting raise/lower, switch/rheostat
e. Voltage regulator
f. Manual off /automatic, Start/stop engine control
g. Alarm panel equipped with first out feature to indicate the following alarms and shutdowns:
(i) Stator winding temperature(s)
(ii) Generator bearing temperatures
(iii) Battery low voltage
(iv) Battery charger Failure
(v) Generator relay trip/lockout
(vi) Over and under frequency
(vii) Emergency stop
Duplication of instruments between the generator control panel and the engine local instrument panel shall be mutually agreed upon, driver manufacturer and generator manufacturer.
All safety or protective alarms shall be wired fail-safe, utilizing field alarm and shutdown contacts that are closed and energized when the generator system is in its normal operation mode.
Alarm and shutdown switches shall be suitable for operation on both AC and DC systems and shall have a minimum current rating of 1 A at 125 V DC or 10 A at 120 V AC.
Diesel Generator Tests
Electrical test procedures shall conform to IEEE 115.
The following tests shall be performed on the generator, exciter, and auxiliaries:
a. Visual inspection
b. Dimensional checks
c. Generator Performance test
d. Exciter field current
e. Insulation resistance of field and armature
f. Measurement of cold resistance of armature and field windings
g. Measurement of rotor impedance
h. Generator phase-sequence and voltage balance
i. Short-circuit tests at reduced voltage to determine reactance and time constants. These tests, or certified test reports on a duplicate generator, shall be required
j. Overspeed trip
k. Temperature tests
l. Dielectric tests and polarization index
m. The dielectric tests described in Paragraph 9.3 of ANSI C50.10 shall be performed on the generator
n. Generator rotor shall be statically and dynamically balanced at a minimum of 600 rpm
o. Exciter rotor shall be balanced in the same manner as the generator rotor
p. Mechanical run of generator and, if applicable, exciter. The generator shall be mechanically run at rated speed for a minimum of 4 hours.
q. During the mechanical operation of all equipment shall function satisfactorily.
r. The job or contract non contacting probes shall be installed for the test and used to determine the vibration levels. Supplier shall be expected to prove the compatibility of the probe and test stand readout equipment.
s. The generator shall be run with the generator unexcited, if possible, at 110 percent and 120 percent of normal operating speed. After the unit has stabilized at these conditions, readings shall be recorded for vibration, oil pressure, and temperature for each operating condition.
t. Piping shall be hydro statically tested to 11/2 times the design pressure
u. Load tests including full load test, for 4 hours, with a load bank of adequate capacity
v. Overload test
w. Functional test of control panel
x. Combined operation test
y. Governor response
Diesel Generator PDF
Power System and Equipment Design Calculations
Main keywords for this article are Diesel Generator Working Principle, Diesel Generator Parts and Functions, Diesel Generator Efficiency, Diesel Generator PDF, Diesel Generator Tests.