Table of Contents

  1. General
  2. Drawings and Data
  3. Generator Design
  4. Accessories Generators
  5. Exciter
  6. Accessories Exciter
  7. Noise Level
  8. Coupling
  9. Winding Temperatures Detectors
  10. Power Factor
  11. Insulation and Windings
  12. Rotor
  13. Bearings and Lubrication
  14. Balance and Vibration
  15. Brushes
  16. Space Heaters
  17. Nameplates
  18. Tests
  19. Assembly
  20. Transport Provisions

1. General

1.1 Description

This specification covers the minimum technical requirements for turbine driven synchronous generators. Additional information for each individual case shall be given in the requisition.

1.2 Standards

Generators shall be design and fabricated in accordance with the latest edition of the National Standard(s) mentioned in the requisition and relevant IEC Publication.

1.3 Site Conditions

Generators have to suit the site conditions mentioned in the requisition and have to withstand a corrosive chemical and refinery atmosphere with a maximum ambient temperature of 40°C and a relative humidity of 90%, unless otherwise specified.

1.4 Conflicting Requirements

In case of conflict between the conditions and documents mentioned above or between these and this specification the severest requirement will govern.

Purchaser is not committed to check vendor’s documents like quotation, order confirmations, drawings, etc. Purchaser will approve these in principle only.

It will remain vendor’s responsibility to make the generators in accordance with the specification in a fully functional and workmanlike manner.

A deviation from this specification is only acceptable in case vendor has specified in his quotation under the heading “deviations from specification” the requirements he cannot meet and Company has accepted this deviation in writing before ordering.

Failure to do so will be interpreted by purchaser as confirmation that manufacturer complies fully with this specification, and any subsequent extra costs that may arise as a result shall be borne by the manufacturer.

2. Drawings and Data

Drawings and other technical data shall be furnished in quantities as specified in the invitation for bids.

2.1 Drawings and Data to be Furnished with the Quotation

2.1.1 All information marked “X” on the requisition data sheet.

2.1.2 A fundamental outline drawing.

2.1.3 Approximate weight

2.1.4 Type(s) of bearings used.

2.2 Drawings and Data to Be Send for Approval after Ordering

Within four weeks after having received the order, vendor has to send dimension drawing showing all dimensions, weight of generator and rotor, exact location of the terminal boxes and filled out requisition data sheet, etc.

2.3 Drawings and Data to Be Send for Construction (Final)

Within two weeks after drawings as per item 2.2 have been returned, vendor has to send same drawings corrected to purchaser.

2.4 Instruction

8 weeks before delivery data indicated in the order, vendor has to supply installation-, operating-, and maintenance instructions.

3. Generator Design

3.1 Rating

Synchronous generator shall be rated on a continuous duty basis, and the rating shall be expressed in kilo volt ampere available at the terminals at 0,8 power factor, unless otherwise specified.

The corresponding kilowatts should also be stated.

3.2 Enclosure

Generator shall be totally enclosed, selfventilated, nonsalient pole with ventilating fan(s) and connections for bottom air intake and discharge, unless otherwise specified.

3.2.1 Generators and accessories shall comply with requirements for the hazardous category specified in the requisition.

In addition the enclosure shall be suitable for the location specified (in/outdoor).

3.2.2 Generators having brushes, commutators or sliprings of use in hazardous location shall be explosionproof or have their brushes, commutators or sliprings enclosed in explosionproof, pressurized or forced ventilated enclosures.

They shall have adequate air flow and other provisions to minimize carbon dust build-up.

3.2.3 Requisition will indicate type of generator enclosure. Type of protection against entrance of foreign particles and water shall be according German DIN 40050 or equivalent standards.

3.2.4 Generator enclosure shall be provided with lifting eyebolts, rings or lugs, capable of supporting the weight of the generator.

3.3 Variations from Rated Voltage

The generator shall operate successfully at rated kVA, frequency, power factor and sinus wave not more than 5% above or below rated voltage.

3.4 Deviation Factors

The deviation factor of the open current terminal voltage wave of the generator shall not exceed 10%, unless otherwise specified.

The deviation factor of a wave is the ratio of the maximum difference between corresponding ordinates of the wave and of the equivalent sinus wave.

3.5 Telephone Influence Factor (TIF)

Only for generators having voltage ratings of 2000 volts and higher.

The TIF shall not exceed the following:

KVA Rating Balanced TIF
300 - 699 250
700 - 4999 150
5000 -19999 100
20000 and above 70
KVA Rating Residual TIF
1000 - 4999 100
5000 -19999 75
20000 and above 50

3.6 Short-Circuit Characteristics

The machine windings, and connections, and terminal leads shall be so protected, insulated and braced as to withstand safety, without displacement of injury, the stresses of a momentary three phase short circuit at its terminals when operated at rated load and voltage, or any other momentary short circuit, provided the machine phase currents under the fault condition are limited by means of resistance to a value which does not exceed the maximum phase current obtained from a three phase fault.
The generator shall be capable of withstanding, without injury, a 30 second 3 phase short circuit at its terminals when operating at rated kVA and power factor.

3.7 Parallel Operation

The generators shall be suitable for mutual and parallel operation with the network system.

3.8 Voltage Regulation

The voltage regulation shall be as defined by NEMA publication TU 4-1952.

Power factor Full load regulation in % (not to be exceeded)
0,8 45
0,9 40
1,0 30

3.9 Overspeed Limitations

The generator shall be so constructed that in an emergency it will withstand, without mechanical injury, an overspeed of 20%.

3.10 Maximum Momentary Overloads

Generator shall be capable of carrying a 1 minute overload of 50% of normal rated current with the field set for normal rated load excitation.

3.11 Class of Insulation

Electrical insulation system shall be as follows:

Armature: Class F

Field: Class F

3.12 Total Temperature

The total temperature for each of the various parts of the generator shall not exceed the following:

Part Total temp.
degrees C
Method of temp. measurement Stated rise
Armature windings 100 detectors 80°
Field windings 120 resistance 80°
Collector rings 120 thermometer 80°

4. Accessories Generators

The generator shall include the following features and accessories:

a. Ventilating fans mounted on the shaft to provide air circulation through a closed ventilated system, including the generator, and the air coolers mounted below the turbine operating platforms. Cooling air will be draw from both ends and blown out through the middle of the enclosure

b. Air coolers using water as cooling medium. The coolers shall be arranged so that they will be completely filled with water during operation. Vendor shall state water requirements

c. Field discharge resistor

d. Field wound for 110 volts

e. Anti-condensate heater

f. Neutral grounding resistor, standard castgrid type for connection in neutral, three phase, 50 cycle circuit. Resistor to withstand operation at rated voltage for 5 seconds without exceeding a temperature rise of 500°C. The resistor shall be mounted below the turbine-generator platform

g. Both ends of each phase of the star-connected stator windings shall be brought out for connection to current transformers for differential protection

h. Resistance type temperature detectors shall be located between upper and lower armature coils in slots containing the different phase windings where highest temperatures are expected. A minimum of six detectors, two per phase, shall be furnished and shall be brought out to a separate terminal box

i. Fabricated base plates for mounting units

j. Two CO2 connections in generator housing

k. One complete set of wrenches and tools.

5. Exciter

The exciter shall be direct connected, either shunt wound or brushless.

5.1 Generators having brushless excitation system with rotating exciters are preferred to excitation system through slipring.

Rectifiers and electronic equipment for the monitoring device shall be suitably designed to operate reliably under the strain due to centrifugal forces. They shall be suitably rated for synchronous operation and also for abnormal duty of fault condition to which the machine may be subjected. All rotating components of the excitation system and monitoring device shall be of robust construction and all connections to be secured against loosening. The arrangement shall afford good accessibility and be well ventilated. Wiring will be minimized and leads are supported mechanically.

5.2 The ventilation shall be by ambient air drawn through a filter. The collector of the generator shall be selfventilated. Exciter voltage stated to be maximum 155 volts.

5.3 The total temperature for each of the various parts of the direct connected exciter, when tested at rate conditions, shall not exceed the following:

Part Total temp. degrees C Method of temp. measurement
Core and windings 80 thermometer
Commutator 95 thermometer
Bare copper windings 90 thermometer

The total temperature is based on 40°C ambient.

6. Accessories Exciter

The exciter shall include the following features and accessories:

a. Field rheostat, hand operated, for mounting on control panel

b. Stabilized shunt wound

c. 110 volts exciter to coordinate with 110 volts generator windings

d. Speed of response not less than 0,5 without pilot exciters

e. Suitable for synchronizing at no load voltage on the synchronous generator under hand control exciter voltage and without the use of a main generator field rheostat.

7. Noise Level

For measuring equipment to determine the noise levels see IEC Publication 179 “recommendation for precision sound level meters”. Noise level to be measured around the machine at a distance of 1 meter from its surface at shaft height.

A measurement of total noise level does not define noise level acceptability, because generator with the same overall decibel noise level may have a different noise quality.

For these reasons generator noise levels shall be specified in terms of: Total noise level.

Maximum acceptable 85 dB (A) Noise level per frequency bands:

Maximum noise level values Maximum level in dB
63 98
125 95
250 93
500 87
1000 82
2000 79
4000 79
8000 82

8. Coupling

Couplings between turbine and generator shall be of the rigid type. Allowance for shaft expansion shall be provided. Continuous lubricating and cooling shall be provided from the lube oil system.

9. Winding Temperatures Detectors

Generator of 2000 kVA and larger shall be provided with winding temperature detectors, 6 per generator. 2 per phase and spaced equally around the circumference of the stator. All leads of these detectors have to be brought out to a connection box. The vendor shall furnish all necessary relays, temperatures indicator, switches, etc., associated with the temperature detectors. These relays will be mounted remotely by the purchaser.

10. Power Factor

Generators shall be designed for factor as specified in the requisition.

11. Insulation and Windings

Class F winding insulation as defined by VDE 0530 is required. However, in addition manufacturer will have to guarantee his insulation suitable for use in a chemical plant and refinery atmosphere in outdoor areas unless otherwise indicated. Stator windings shall be fully insulated for an undergrounded neutral system.

12. Rotor

Depending on the speed, bolted-on or dovetailed poles shall be employed being built up of laminated steel plate. No welding of the rotor to the shaft is acceptable. Rotor shall be balanced statically and dynamically to a high degree of to the accuracy.

13. Bearings and Lubrication

Oil lubricated sleeve bearings shall be supplied on all generators larger than 500 kVA for 3000 rpm and larger than 1000 kVA for 1500 rpm. Generators with sleeve bearings shall have provisions for testing the air gap at each end of the generator.

Design of sleeve bearings shall permit bearing replacement without removing the bottom bearing bracket.

Bearing housings shall have oil reservoirs of sufficient depth to serve as settling chambers. Recommended oil level shall be marked on the outside of bearing housings by a cast mark or a metal tag.

Where forced feed lubrication is furnished, lubrication oil system shall include the following:

a. Separate motor driven oil pump with 380 volts, 3-phase, 50 c/s electric motor according to purchaser’s specification for electric motors.

b. Oil pressure controller and by-pass relief valve if oil pumps is possible displacement type.

c. Oil cooler of sufficient radiating service or oil reservoir for adequate cooling.

d. Duplex filters to permit changing filter element without shutting down. If oil ring and sufficient oil capacity in each bearing housing are provided to permit at least 30 minutes operation with the forced feed lubrication system inoperative, a single filter is acceptable.

e. Oil pressure gauge downstream of filter.

f. Dial type temperature indicator for the bearing. Indicator shall be mounted on the generator enclosures with bulbs arranged to measure the same temperature as that to which the temperature shut down and alarm device are sensitive.

g. Sight flow indicator in oil return line to reservoir from each bearing.

h. Low oil flow shutdown and/or alarm device execution confirming to hazardous requirements as specified. The operating temperatures shall be stamped on the tagplate and mounted on the generator enclosure.

i. All piping shall be thoroughly cleaned and coated with approved rust preventative before shipment.

j. Reservoir shall be thoroughly cleaned and coated with approved rust preventative before shipment.

When it is specified that the lubricating oil system for generator and turbine is combined, generator manufacturer has only to supply equipment mentioned under f. and g. above.

In addition to the generator manufacturer has to specify:

a. Viscosity and kind of oil required

b. Oil pressure and quantity per hour he requires.

For generator having insulated bearings, insulating fittings shall be provided in the oil supply connections to prevent the oil supply line from bypassing the bearing insulation. If ball and/or roller bearings are mounted as vendor’s standard design, vendor has to give a make and type of the bearings and also lubrication instructions. Ball and roller bearings shall be in metric sizes.

14. Balance and Vibration

Rotor and fan to be dynamically balanced, and where applicable with half coupling mounted on the shaft. For vibration see German VDI 2056. Maximum acceptable vibration velocities:

Group “Stufe”
K 0,71
M 1,12
G 1,8
T 2,8

Rotor and fan have also to be statically balanced to ensure a smooth running-out of rotor. Rotors shall be given a corrosion resistant coating after balancing. Half couplings may not be used for balancing of the generator.

15. Brushes

It must be possible to change brushes of the exciter and sliprings when generator is fully loaded without any danger or special precautions. Life time of brushes will be at least 6 months under normal running conditions.

16. Space Heaters

Generally space heaters have only to be provided if they are required due to vendor’s design or when specified in the requisition. Location and capacity of heaters shall be as required to prevent condensation in the generator when it is not operation. Supply voltage maximum 240 volts. Maximum permissible temperature of the space heater will be 200°C unless a lower temperature is specified in view of explosion danger. The space heater leads have to be brought out into a separate terminal box, located near the main terminal box.

17. Nameplates

For all generators the nameplate has to show in addition the generator manufacturer’s or the bearing manufacturer’s identification of all bearings and also the regreasing period and brand and type of grease or oil, replacement or cleaning air filters. Nameplates and dataplates shall be stainless steel, brass or bronze.

18. Tests

18.1 Generator is subject to inspection or tests at any time during manufacture by purchaser’s inspectors at the factory.

18.2 Supplier has to furnish certified test report of an official laboratory when generators are mounted in hazardous areas.

18.3 Following tests shall form part of the order and have to be carried-out by vendor.

18.3.1 Resistance of field and armature.

18.3.2 Polarity of field coils.

18.3.3 Measurement of air gap by gage.

18.3.4 Inspection of bearings and mechanical operation.

18.3.5 Check no load field current at normal voltage and frequency.

18.3.6 Determination of temperature rise.

18.3.7 Determination of efficiency, including the determination of armature and field I2 losses, core losses, friction and windage losses and stray load losses.

18.3.8 Determination of efficiency at 3/4 and full load.

18.3.9 Measurement of rotor inertia.

18.3.10 Overspeed test.

18.3.11 High potential test on field and armature.

18.3.12 Measurement of insulation resistance with one 2500 volts motor driven Megger.

18.4 In addition to the test mentioned above, generator of 1000 kVA and up are subject to noise level tests. In this case a noise level diagram has to be attached to the test reports.

18.5 Vibration test.

19. Assembly

Shaft ends and other bare metal parts shall be coated with an easily removable preventative liquid. Bearing shall be slushed with a suitable rust preventive liquid. Manufacturer has to make provisions to prevent damage of bearings during transport.

20. Transport Provisions

It is the vendor’s complete responsibility to deliver the generator on site, or where specified by the purchaser, in a complete functional condition. In no way it is possible for the vendor to avoid this responsibility.