Self-regulating brushless synchronous alternators series DIG
Contents:
1.
Applications
2.
Ratings
3.
Definition of the alternator 3.1 Basic technical data 3.2 Enclosure 3.3 Cooling method 3.4 Design
4.
Mechanical features 4.1 Construction 4.2 Stator 4.3 Rotor 4.4 Bearing plates 4.5 Bearings 4.6 Terminal boxes
5.
Derating factors 5.1 Standard conditions 5.2 Relation between power and coolant temperature 5.3 Relation between power and installation altitude 5.4 Relation between power and cos phi: 5.5 Marine classification 5.6 Higher types of enclosure 5.6.1 Enclosure IP 43 5.6.2 Enclosure IPR 44 or IPR 54 5.6.3 Enclosure IP 44 or IP 54 Electrical functions 6.1 Operating principle 6.1.1 Alternator 6.1.2 “COSIMAT N+” voltage regulator 6.2 Self-excitation, de-excitation 6.2.1 Self-excitation 6.2.2 De-excitation 6.3 Voltage and frequency 6.3.1 Voltage adjustment range 6.3.2 Steady-state voltage performance 6.3.3 Transient voltage behaviour 6.3.4 Voltage waveform 6.4 Currents 6.4.1 Asymmetrical loads 6.4.2 Overload 6.4.3 Short-circuit behaviour 6.5 Harmonic load 6.6 Emergency operation 6.6.1 Emergency manual operation 6.6.2 Stand-by control 6.7 Star point connection, neutral current
6.
7.
Parallel operation 7.1 General 7.2 Conditions for parallel operation 7.3 Start-up synchronisation for isolated parallel operation 7.4 Stationary operation / load distribution 7.4.1 Voltage droop 7.4.2 Power factor regulation 7.5 Parallel mains operation 7.6.Oscillations
8.
Features of the medium voltage winding 8.1 General 8.2 Design and manufacture
9.
Factory tests 9.1 Standard tests 9.2 Special tests (at extra charge)
2
AVK SEG Competence in power generation and system protection AVK SEG is a competent, reliable partner in power generation and protection technology. We offer the quality and flexibility of a medium-sized, independent group of companies, which perfectly combine the experience gained through many years with a policy of innovative development. Active on a global basis, we supply not only a comprehensive range of products, but also customer-specific engineering. Our product programme extends from individual protection devices through to complete electrical equipment for power plants. AvK Deutschland, the German company with its plant in Ingolstadt and a branch in Dreieich near Frankfurt, supplies synchronous machines and converters, whilst SEG Kempen specialises in protection and functional equipment. Together we set new standards and exert an active influence on international power-generation technology. No matter what scope of services you are looking for, we can deliver it – an individual device, an alternator or a complete turnkey system. Our extremely efficient customer service and advisory sales offices located across the globe will make every effort to comply with your requirements. We not only build from a base of technological continuity and quality, but also place particular emphasis on customer satisfaction. The certification of the AvK and SEG plants in accordance with German industrial standard DIN EN ISO 9001 underlines the importance we attach to quality. 3
Series DIG Self-regulating brushless synchronous alternators 1. Applications
Typical applications
AvK synchronous alternators from Series DIG 110 – 191 are used in the following areas of application:
● Continuous supply to stationary and maritime plants ● Parallel peak-load operation ● Emergency supply to important consumers such as power stations, industrial plants, hospitals and tower blocks ● Combined heat and power stations (CHP) ● Electrical supply systems on board ship ● Diesel-electric drives for ships ● Special-purpose supplies to consumers with high mains-supply quality requirements ● No-break power systems (UPS) ● Frequency conversions, e.g. 50:60 Hz They can be used with all types of drive system: diesel engines, gas engines, gas, hydraulic or steam turbines and as shaft generators on board ship.
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2. Ratings in accordance with VDE 0530, enclosure IP 23, criteria as in Item 3.1
Voltage Frequency Frame size No. of poles
50 Hz Speed rpm
60 Hz Speed rpm
3.3 kV 50 Hz Rating (kVA)
4.16 kV 60 Hz Rating (kVA)
6–6.6 kV 50 Hz Rating (kVA)
10–11 kV 50 Hz Rating (kVA)
13.8 kV 60 Hz Rating (kVA)
750 – 1080 580 – 750
900 – 1300 720 – 940
750 – 1080 560 – 720
750 – 1080 –
– – – – – –
DIG 110
4 6
1500 1000
1800 1200
DIG 120
4 6 8 10
1500 1000 750 600
1800 1200 900 720
1300 – 2050 1630 – 2600 1300 – 1750 1150 – 1650 900 – 1520 1130 – 1900 880 – 1200 1300 750 – 1130 940 – 1410 – – 600 – 960 750 – 1200 – –
DIG 130
4 6 8 10 12
1500 1000 750 600 500
1800 1200 900 720 600
2250 – 1730 – 1180 – 990 – 790 –
3850 2650 1950 1550 1180
2850 – 2000 – 1470 – 1240 – 990 –
4000 1900 – 3000 1800 – 2800 2050 – 3250 3300 1450 – 2250 1350 – 2100 1600 – 2550 2450 1140 – 1650 1300 – 1600 1700 – 1900 1700 800 – 1300 1060 – 1200 1400 1470 650 – 1000 1080 –
DIG 140
4 6 8 10 12
1500 1000 750 600 500
1800 1200 900 720 600
4000 – 3050 – 2100 – 1850 – 1410 –
5600 4050 3080 2200 1880
4850 – 3800 – 2600 – 2000 – 1760 –
7000 5050 3850 2750 2300
3000 – 2400 – 1800 – 1400 – 1150 –
4600 3500 2650 2100 1500
3000 – 2200 – 1800 – 1250 – 1150 –
4400 3250 2600 2100 1550
3400 – 2700 – 2050 – 1550 – 1480 –
5000 4000 3050 2150 1650
DIG 150
4 6 8 10 12
1500 1000 750 600 500
1800 1200 900 720 600
5800 – 4600 – 3300 – 2500 – 2000 –
7400 5200 4500 2800 2650
7200 – 5750 – 4200 – 3200 – 2500 –
8100 6500 5000 3550 3300
5100 – 3550 – 2800 – 2200 – 1700 –
6850 5500 4800 3300 2600
4800 – 3450 – 2850 – 2150 – 1750 –
6050 4950 4500 3000 2500
5400 – 4150 – 3300 – 2500 – 1900 –
6000 6100 4600 3600 2750
DIG 156
4 6 8 10 12
1500 1000 750 600 500
1800 1200 900 720 600
7700 – 5600 – 4700 – 3000 – 3250 –
9600 7850 6400 4100 4750
9700 –11100 7050 – 9900 5400 – 8050 3700 – 5100 3400 – 6000
7300 – 5600 – 4700 – 3400 – 2800 –
9600 7800 6800 5300 4650
6600 – 5300 – 4400 – 3200 – 2500 –
8800 7500 6700 5450 4300
6700 – 6600 – 5200 – 4100 – 2950 –
8800 8800 7000 5500 4600
DIG 163
4 6 8 10 12
1500 1000 750 600 500
1800 1200 900 720 600
10100 –12600 – 8200 –10500 10200 –13300 7000 – 7500 7950 – 8400 5400 – 6700 6800 – 8200 5300 – 6150 6400 – 7300
DIG 171
6 8 10 12 14
1000 750 600 500 429
1200 900 720 600 514
10400 –13000 12500 –16000 10400 – 2100 10400 –12100 12500 –14600 7800 –11150 8550 –14400 9200 –15800 8600 –13350 9800 –12800 7200 –12100 9000 –13000 7400 –11700 6900 –11400 8300 –11600 5800 –10200 7400 –12800 6050 –10600 5800 –10200 6500 – 9800 4600 – 9500 5600 –10150 4300 – 9300 4200 – 8500 5100 – 8700
DIG 181
10 12 14 16 18
600 500 429 375 333
720 600 514 450 400
– – – – –
– – – – –
DIG 191
10 12 14 16 18
600 500 429 375 333
720 600 514 450 400
– – – – –
– – – – –
9650 –14300 10500 –14100 7800 –10500 7750 –10300 7050 – 8550 6850 – 8400 5650 – 7400 5650 – 7100 4750 – 6050 4350 – 5850
– 9500 –12000 7950 – 9200 6200 – 8300 5000 – 6200
12200 –18700 13800 –18700 13600 –21100 11200 –15450 11200 –15450 11700 –15600 8700 –13500 7950 –13000 9700 –13000 – 7600 –12000 8700 –12200 – 6600 –11400 7850 –11800 – – – – –
19400 –25700 22000 –27800 16000 –22700 16300 –23300 14800 –19700 15200 –21200 12900 –16900 13900 –18300 11100 –15400 13100 –16400
5
3. Definition of the alternator
Specification to German Industrial Standards DIN – EN 60034, VDE 0530, IEC 34
3.1 Basic technical data Rated power:
See listed ratings
Rated power factor:
cos phi 0.8
Rated voltage:
3...15 kV
Rated frequency:
50 Hz resp. 60 Hz, special frequencies available on request
6
Coolant temperature:
40° C (VDE)
Installation altitude:
≤ 1000 m a sl (VDE)
Enclosure:
See 3.2
Cooling method:
See 3.3
Design:
See 3.4
3.2
3.3
Enclosure IEC 34-5 DIN VDE 0530 - 5
Cooling method IEC 34 - 6, DIN VDE 0530 - 6
Standard IP 23. Higher types of enclosure such as IP 43, IPR 44, IPR 54, IP 44 and IP 54 can be supplied on request; see Section 5.6 for further details.
Standards are: IC01/IC0A1, IC11/IC1A1, IC21/IC2A1, IC31/IC3A1, IC616/IC6A1A6, IC81W/IC8A1W7. In cases where special enclosures are asked for, we can adapt the cooling method as appropriate.
Deviations from the above data and VDE 0530, in order to adapt the alternators to suit the client’s specific requirements, conditions and specifications, can be undertaken on request. This includes different type classifications in relation to rated power from those shown in the listed ratings. Alternators can be built to comply with international guidelines such as BS 4999, CIE 2/3, NF 51100, NEMA and to marine classification regulations as in Section 5.5.
3.4 Design IEC 34 - 7 DIN VDE 0530 - 7 We manufacture the DIG 110 and DIG 171 as standard frame sizes in IMB3, IMB 20 and IM 1305 (B 16). Frame sizes DIG 181 and DIG 191 are supplied as standard in IM 7201 and IM 7211 with two pedestaltype bearings. Other designs are possible. Special mounting dimensions can be adapted to suit the supporting frame of the complete machine assembly.
B3 IMB 3 IM 1001
B 20/B 5 IMB 25
B 3/B 5 IMB 35 IM 2001
B 16 IM 1305
B 20 IMB 20 IM 1101
B2 IM 1205
B 20/B 14 IMB 24
V1 IMV 1 IM 3011
Design
B3
B3/B5
B20
B20/B14
B20/B5
B16
B2
V1
B3/B14
D9
Code I
IMB 3
IMB 35
IMB 20
IMB 24
IMB 25
_
_
IMV 1
IMB 34
_
Code II
IM 1001
IM 2001
IM 1101
IM 1305
IM 1205
IM 3011
IM 2101
IM 7201
DIG 110 to DIG 156
●
●
●
●
●
●
●
DIG 163 DIG 171
●
●
●
●
DIG 181 DIG 191
●
●
●
Special design
● ● ●
●
7
Antifriction bearing design
4. Mechanical features
1
Shaft
7
Fan
2
External bearing cap
8
Stator housing
3
Grease regulation disc
9
Main alternator stator
13
Bearing plate, NDE
4
Antifriction bearing DE
10
Main alternator rotor
14
Antifriction bearing NDE
5
Internal bearing cover
11
Stator exciter
15
Rectifier cover
6
Bearing plate, DE
12
Rotor exciter
16
Rectifier support
Sleeve bearing design
8
1
Shaft
7
Bearing plate, DE
2
Labyrinth seal
8
Fan
13
Rotor exciter
3
Sleeve bearing, DE
9
Stator housing
14
Bearing plate, NDE
4
Sleeve bearing shell
10
Main alternator stator
15
Sleeve bearing, NDE
5
Lubricating ring
11
Main alternator rotor
16
Rectifier cover
6
Sleeve bearing cap
12
Stator exciter
17
Rectifier support
4.1
4.2
4.3
4.4
Construction
Stator
Rotor
Bearing plates
The alternator consists of a main internal-pole alternator and an external-pole exciter. On DIG 110 to 171 alternators rated for voltages of ≤ 11.5 kV, power is supplied by an auxiliary exciter winding in the primary stator to the voltage regulator. For rated voltages > 11.5 up to 15 kV, an auxiliary exciter takes over this task.
The stator housing, which is of welded construction, contains a stator core made up of low-loss dynamo steel sheets, pressed together by means of pressure plates to form a compact unit. The resulting rigid construction takes the specific operating conditions of diesel-electric units into consideration.
The main salient-pole rotor is made up of metal sheets or steel plates pressed together. A copper damper cage is installed as standard and electrically connected to the pole shoes and from pole to pole. The main salient-pole rotor winding is made from
DIG 110 to DIG 171 frame sizes are fitted with welded or cast iron bearing plates. The alternator feet are mounted in close proximity to the bearings, and are of suitable size and shape in order to guarantee a particularly rigid foundation. In the DIG 140, 150 and 156 frame sizes the alternator’s mounting feet together with the bearing plates form a combined housing component. In the DIG 181 and 191 frame sizes the pedestal-type bearings are located on a platform bolted on to the machine’s frame. As a result the stator and rotor form an integral unit, which can be transported without any problem and set into a suitable foundation by means of the appropriate lifting gear.
For DIG 181 and DIG 191 frame sizes, we use – depending upon the area of application – an auxiliary exciter or an auxiliary exciter winding. Special versions are produced to customer’s order.
The stator winding complies with temperature class F in accordance with German Industrial Standard DIN EN 60034 – 1 and VDE 0530 – 1. The winding overhangs and connections are supported by fastening elements and firmly linked by mechanical means to guard against loads caused by electrodynamic forces.
copper profile and protected against deformation caused by centrifugal forces by suitable and generously-sized components. The exciter rotor consists of dynamo steel sheets with the three-phase winding incorporated into its slots. The rotor windings comply with temperature class F in accordance with German Industrial Standards DIN EN 60034 – 1 and VDE 0530 – 1. Standard balancing of the rotor is carried out according to VDE 0530 / IEC 34 – 14 with half key. Other shaft designs can be supplied at customer’s request.
9
4.5 Bearings The standard bearings in the DIG 110 to 156 frame sizes are of antifriction design, with an expected service life of at least 30,000 hours for stationary operation. The DE is equipped with roller bearings and the NDE with either deep-groove ball bearings or these bearings combined with roller bearings. All bearings are suitable for regreasing and have a grease volume control system. Whereas these types of alternator can be supplied at extra charge with sleeve bearings, the DIG 163 to DIG 171 are always supplied with sleeve
10
bearings flange-mounted to the bearing plates, and fitted as standard with a lubricating ring for self-lubrication. Depending upon the application it may be necessary to provide forced oil lubrication or water cooling. The DIG 181 and 191 frame sizes are supplied with pedestal-type sleeve bearings on the DE and NDE. DIG alternators of dual-bearing design are always fitted with a fixed bearing and a floating bearing. If antifriction bearings are used, the fixed bearing is at the NDE. With plain bearings, it is at the DE. DIG alternators of single-bearing design have a floating bearing at the NDE. Appropriate fastening elements ensure that all bearings are protected during transport. Similarly, for reasons of safety, all sleeve bearing alternators are made ready for transport without oil.
4.6 Terminal boxes The main terminal boxes are mounted on top or at the side of the alternator in accordance with the customer’s requirements and enclosed to IP54 standard with the power cable outlet at the stipulated point. Of the standard design’s four terminals, three are for the U1, V1 and W1 power outputs and one for the star-point connection to the three U2, V2 and W2 windings. If necessary, for example in order to install current transformers for differential protection and measurements, a larger terminal
box can provided. Current transformers installed by AvK / KWK have a copper busbar which forms the fourth terminal (N). Depending upon the size of the alternator, the low-voltage terminals are located either on the bearing plates at NDE or in a separate terminal box on the stator housing. Regulator, temperature sensors, secondary current transformer outputs, exciter current measuring leads, heater and similar equipment can be connected here. Heating terminals which remain live when the alternator is shut down are of safe-to-touch design.
5. Derating factors
5.1
5.2
Standard conditions
Relation between power and coolant temperature: Characteristic curve 5.2
Relation between power and installation altitude Characteristic curve 5.3
The decisive factor here is the winding’s temperature limit. A reduction in coolant temperature < 40°C will result in an increase in power, an increase in coolant temperature > 40° C in a power reduction. The characteristic values of the selected alternator, for example reactances, apply in all cases to the pre-defined power rating (SN).
As an increase in altitude affects air density and as a result the air’s ability to absorb heat, it is necessary either to reduce the power or select a larger alternator.
The listed ratings refer to VDE standard conditions, i.e.: Coolant temperature = 40°C Installation altitude ≤1000 metres above sea level, and in accordance with AvK standard: Enclosure rating IP 23 Cooling method IC 01
Relation between power and coolant temperature
5.3
Characteristic curve 5.2
Relation between power and installation altitude
Characteristic curve 5.3
∂ [°C]
11
5.4
Relation between power and cos phi
Characteristic curve 5.4
Relation between power and cos phi : Characteristic curve 5.4 The under-excited range cos phi 0 – 1 is limited at:
The over-excited range is limited between:
●
single operation maintaining the rated voltage by the voltage regulator
●
cos phi = 1 - 0.8 by the prime mover’s power
●
parallel operation by stability against desynchronisation
●
cos phi = 0.8 - 0 by the permissible rotor temperature rise.
under-excited
over-excited
Limited by alternator Limited by prime mover
5.5 Classification regulations
CT °C
Owing to the fact that coolant temperature is higher and the permissible temperature rise lower than according to the regulations pertaining to land-based operation, it is necessary to reduce the power or to increase the size of the alternator.
Germ. Lloyd
45
100
RINA
50
90
0,925
American Bureau of Shipping
50
95
0,96
Bureau Veritas
50
90
0,925
Det Norske Veritas
45
90
0,925
Lloyds Reg. of Shipping
45
951) 902)
0,925
The adjacent table is applicable for permissible temperature rises with design and utilisation in accordance with temperature class F. Please provide us with details if types of enclosure are higher than IP 23 and additional requirements apply.
Register USSR
45
95
Marine classification
12
Information:
Temperature rise SNom/SType K 0,96
0,96
DIN VDE 0530 -1 Coolant temperature 40° C, temperature rise 105 K for ≤ 5 000 kVA temperature rise 100 K for > 5 000 kVA 1 2
) ≤ 5 000 kVA ) > 5 000 kVA
5.6
5.6.2
5.6.3
Higher types of enclosure
Enclosure IPR 44 or IPR 54
Enclosure IP 44 or IP 54
Design and electrical measures are laid down during the project stage. The rating plate contains details of the enclosure and the rated power.
An additional advantage – in addition to the higher protection level – is the fact that the required cooling air is discharged from the installation area by air ducts, which also helps to reduce the noise level. The alternator’s air inlets and outlets are designed to facilitate the attachment of intake and discharge ducts. The permissible pressure loss in the ducting must be co-ordinated with the manufacturer.
These types of enclosure require the use of heat exchangers. Of primary significance for the alternator is the temperature of the cooling air leaving the cooler and entering the alternator.
5.6.1 Enclosure IP 43 The IP 43 enclosure requires the provision of a dust filter, which increases air resistance so that power is reduced by 5 %. Temperature sensors in the alternator, which are connected to a dripping device on the switchgear, detect any unacceptable rise in winding temperature when the dust filter is due for cleaning.
●
Water-cooled heat exchanger: In a conventionally designed heat exchanger, the cooling air temperature as it enters the alternator is 15° C higher than the water temperature when it enters the exchanger. The power variation can be seen in characteristic curve 5.2. No power reduction results from the increase in the cooling circuit’s air resistance.
●
Air-cooled heat exchanger: In this case, the temperature of the air leaving the cooler and entering the alternator is higher than the outside air by the amount represented by the temperature drop in the heat exchanger. In a conventionally designed heat exchanger, the cooling air temperature as it enters the alternator is 15° C higher than the air temperature when it enters the cooler. The power reduction can also be seen in characteristic curve 5.2. Increased air resistance will result in a power reduction if the alternator’s cooling system has been designed in an extremely compact manner. For this reason, it is recommended to undertake a precise analysis of requirements and to select the relevant machine rating in each case.
13
6. Electrical functions
6.1
6.1.1
Operating principle
Alternator With auxiliary exciter machine G1
Main machine
T6
Current transformer
G2
Exciter machine
T24
Instrument transformer
G3
Auxiliary exciter machine
R1
Set-point potentiometer
Voltage regulator
With auxiliary exciter winding T6
Current transformer
G1
Main machine
T24
Instrument transformer
G2
Exciter machine
T32
Isolating transformer
G3
Auxiliary winding
R1
Set-point potentiometer
Voltage regulator
14
The auxiliary exciter machine/auxiliary exciter winding G3 supplies the brushless three-phase AC exciter G2 with current via the voltage regulator’s control element. The voltage generated by the three-phase exciter rotor winding is rectified in a three-phase silicone-diode bridge circuit and fed to the rotor of alternator G1. Voltage regulation of the primary alternator at fluctuating loads is carried out by altering the exciter current in the G2 winding by using the voltage regulator’s transistor control element.
6.1.2 “COSIMAT N+” voltage regulator The “COSIMAT N+”, a standardised module, is set up on the alternator in the test field and a functional test is carried out. Voltage is supplied to the regulator via an auxiliary winding in the primary rotor or an auxiliary exciter machine.
In order to record unequal phase voltages arising during asymmetrical loads, the alternator voltage is measured over three phases. The voltage regulator uses exciter current IK1 in exciter’s winding G2 to keep the voltage across the main machine’s terminals at a constant level. A special leaflet describes the COSIMAT N+ voltage regulator in greater detail. The COSIMAT N+ is also available with additional regulators and modules should special operating functions be required.
6.2 Self-excitation, de-excitation 6.2.1 Self-excitation ●
●
The control signals for the following functions are fed in via the terminals on the COSIMAT N+: cos phi regulation/ balancing ● reactive power control/ balancing ● extension of adjustment range ● automatic stand-by changeover ● U/f control ● current-limiting control ● exciter-limiting control ● cable compensation
For alternators ≤11.5 kV with an auxiliary exciter winding, self-excitation is by way of permanent magnets in the exciter.
●
For alternators with auxiliary windings, this voltage should be applied to the exciter’s I1 - K2 terminals during the run-up to the rated speed. A blocking diode is needed.
In alternators with auxiliary exciters the external voltage should be briefly applied to terminals I2 K2 of the exciter. The alternator must be running at rated speed.
6.2.2 De-excitation ●
For alternators > 11.5 kV with auxiliary exciters, self-excitation occurs via the natural rotor remanence and the optimised voltage of the auxiliary exciter’s stator. In special cases, excitation can be obtained by applying an external voltage of approximately 10 V DC (positive pole to the I terminal). External excitation should not be active when the alternator is at a standstill.
●
These devices are described in additional leaflets.
●
●
The current in the exciter G2’s winding IK1 must be reduced to 0 for deexcitation to occur. For this purpose, the power supply to the regulator must be disconnected by removing the jumpers or by resetting a switch as shown in the circuit drawing. Disconnection must always be on the controller’s input side at UH1 – UH1’ and WH1 – WH1’. The switching contacts must be rated for 10 A and 220 V AC. Please comply with the instructions on the relevant circuit diagrams.
Caution: The alternator generates a remanence voltage of app. 15 % of UN after de-excitation. This value is in excess of the permitted contact voltage limit!
6.3 Voltage and frequency AvK alternators for voltages up to 15 kV are built to the specifications laid down by German VDE 0530 and other national standards for 50 or 60 Hz frequencies. However, our versatility enables us to provide other voltages and frequencies on request. 6.3.1 Voltage adjustment range DIG alternators are supplied as standard with a set-point adjuster, which is installed in the switchgear for ease of use. As a result, the voltage is infinitely adjustable. In accordance with German standard VDE 0530, the adjustment range is ± 5 % of the rated voltage and can be extended ±10 % for operational testing of switchgear components and synchronisation. The resistance of the potentiometer’s wires can be disregarded if the conventional distance between the unit and switchgear is not exceeded. Screened cable must be used for the connections. The voltage range between no load and full load in accordance with German VDE 0530, IEC 34 standards is (0.95 - 1.05) x UN with the limitations as layed down in theese standards.
15
6.3.2 Steady-state voltage performance The voltage accuracy is ± 0,5 % to ± 1 % subject to the following conditions/ influencing values: ●
No load to nominal load at cos phi 0.11) … 1
●
Machine cold or warm
●
Drop in speed of app. 3%
1
) This refers to the regulating characteristic. The thermal rating for continuous operation is for cos phi 0.8. The usual operating range is cos phi 0.8 … 1.
6.3.3 Transient voltage behaviour See oscillogram 1 Load application See oscillogram 2 Load shedding The transient voltage variation under fluctuating load is dependent on alternator G1’s reactance voltage drop.
The magnetic circuit and the winding ratings are optimised for low transient voltage fluctuations. The relative current surge and power factors are the external influencing factors for the transient voltage fluctuations. Application of full load at cos phi 0.8 results in a transient voltage drop of app. 18...25 %. The smaller value applies to machines with 1500 rpm, the large value applies to slow-running machines at 500 rpm. The transient voltage fluctuation is slightly lower at base load than when the alternator is running off-load. The voltage-time characteristic is governed by the alternator G1’s time constants, the exciter G2, the regulating system and the external influence exerted by a dynamic drop in speed. The generously sized exciter system achieves short transient recovery times, owing to the excessive excitation effect provided by the power supply during the recovery period up to nominal voltage. Transient recovery time, depending on alternator size, is 0.5...0.8 seconds.
16
Oscillogram 1 / Load application
Alternator DIG 150l/8 3300 kVA 11kV 50 Hz 750 rpm Load application 1000 kVA cos phi = 0.1
Oscillogram 2 / Load shedding
Alternator DIG 150l/8 3300 kVA 11kV 50 Hz 750 rpm Disconnection of 1000 kVA cos phi = 0.1
6.3.4 Voltage waveform The geometry of the magnetic circuit and the winding factor selection of the stator winding combine to generate a sine-wave voltage waveform. The conventional definitions are as follows: ●
Telephone harmonic factor “THF”
The requirement laid down by the German VDE 0530 standard is easily maintained. ●
Harmonic content
The harmonic content is ≤ 2 % measured between phases at no load up to nominal load and power factor of cos phi 0.1… 1 under symmetrical and linear loads. The winding is optimised in order to keep the 5th and 7th harmonics measured between the phases as low as possible. The 3rd harmonic however, depending on load, increases from ≈ 2 % to ≈ 10 % measured between phase and neutral. This does not occur in star
connections measured between phases, as the phase voltages equalize each other. A specially custom-designed winding reduces the harmonic content below 3 % and the percentage of individual harmonics to less than 2 % – also for voltage curve between phase and neutral. This however necessitates a power reduction of app. 10 %. 6.4
An asymmetrical load causes voltage asymmetry and additional losses, which have a distinct effect on the damper cage’s rise in temperature. The load should therefore be allocated to the three phases in as symmetrical a manner as possible. The voltage asymmetry ∆UUN is app. ± 6 % in loading case a. (VDE 0530) The voltage asymmetry ∆UUN is app. ± 4 % in loading case b. (VDE 0530) ●
Currents 6.4.1 Asymmetrical loads The alternator’s electrical layout also permits an asymmetrical load. ●
Asymmetrical loads without loading the other phases are permitted in the following cases: a) 60 % of the rated current measured between phase – neutral b) 35 % of the rated current measured between phases In this case the ratio of the negative-phase sequence system I2 to the rated current IN is 20 % and distinctly higher than the German VDE specifications.
If additional currents are applied to the other phases, the values of the positive-, negative- and zerophase sequence systems must be recorded analytically or graphically in order to ascertain the actual alternator load. The current may not exceed the rated current in any of the winding phases in the alternator and the relationship of the negative-phase sequence system I2 to the rated current IN must remain below 20 %.
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6.4.2 Overload ●
In accordance with German VDE 0530 standard, the alternators must be able to withstand 1.5x the nominal current for a period of 30 seconds.
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To match the requirements for internal combustion engines an overload of 1.1 x nominal current is prescribed for 1 hour within an overall 6-hour period.
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The generously sized exciter equipment allows a short-time overload of 1.8 x the nominal current for a period of 10 seconds without an abnormal drop in the nominal voltage. This overload capability is, for example, available in form of starting current for asynchronous motors.
AvK recommends limiting I2 / IN for protection of the overall system to ≤ 0,08 in accordance with the applicable standards.
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6.4.3 Short-circuit behaviour ●
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The relevant machine parameters are designed so that the peak shortcircuit current is low. Depending upon machine size, it decays to the sustained short-circuit current level within a period of 0.3...0.6 seconds. The relevant components are suitably dimensioned to ensure that in the case of a three-phase shortcircuit between terminals, the alternator supplies 2.5 to 4 x the nominal current for a period of 3 seconds. In the event of a two-phase short-circuit between terminals, the sustained short-circuit current rises by a factor of between 1.4...1.7. This ensures selectifity of the protection devices .
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The range IK = (3...6) x IN for example is generally requested by marine classification societies. When the short-circuit is cleared the resulting excitation leads to a transient voltage increase which almost reaches ceiling voltage. This voltage increase is also possible during certain interruptions to the voltage regulator system. Suitable protective measures for the consumers must be provided for in the switchgear.
6.5 Harmonic load Current rectifiers, as consumers with non-linear load currents, cause harmonics to occur in the voltage curve. In order to minimise the resulting alternator and system losses, and to ensure that the operation of all electrical equipment connected to the system is not compromised, the harmonic content of the voltage curve should be kept as low as possible, see also Section 6.3.4.
Oscillogram/peak short-circuit current
Short-circuit current characteristic for a short circuit between three phases of a DIG alternator 130g/6 1450 kVA 6,6kV with a nominal current of = 419 A 127 A, IKD 3ph
For this purpose, a low sub-transient reactance xd” is required. This can be achieved by using a damper cage of suitable dimensions. If a very high proportion of the load is caused by rectifiers, it may be necessary to enlarge the size of alternator and use a specially designed magnetic circuit. This automatically results in an increase in the peak short-circuit current. The measures required at the alternator are dependent upon the relative non-linear
load, enforced current harmonics at the consumer end and the permissible output voltage distortion factor. 6.6 Emergency operation In order to satisfy certain safety requirements, it is possible to operate the alternator by means of emergency manual controls in the event of a voltage regulator breakdown, or it can be switched over to a stand-by regulator either manually or automatically.
6.6.1 Emergency manual operation The current delivered by the power supply is fed to the exciter winding I1 – K1 of the exciter G2 via a variable voltage transformer with a rectifier connected in series. A rheostat of app. 300 W can also be used in place of the variable-voltage transformer. Manual compensation to correct exciter output proves to be extremely difficult, particularly in cases of sudden peak loads. Emergency manual operation is therefore only possible when an isolated network has negligible fluctuating loads or in system operation parallel with the mains. 6.6.2 Stand-by control Using stand-by control eliminates the inherent disadvantages of the emergency manual operation owing to the fact that after switching to this control the alternator can continue to operate in an unaltered condition.
The entire control unit – primary control, stand-by control, manual or automatic changeover device – must be mounted in the switchgear. 6.7 Star point connection/neutral current DIG alternators are rated in accordance with German VDE 0530 – 1 standard. They can be operated with directly earthed or non-earthed neutral points. The type of neutral earthing is determined by the network’s protection specifications and not by the alternator. Here is some information on the various ways to earth a neutral point (direct earthing): a) Impedance earthing (solid earthing): When earthing several points, e.g. an alternator neutral point and transformer neutral point or several alternator neutral points, excessive currents circulating in the earthing system generated by harmonics – mainly of
odd-numbered orders – cause thermal overloads on the windings and, in particular, the neutral terminals. It may be necessary to use neutral reactor coils to reduce these currents. In the event of a phase short-circuiting to earth, extremely high currents can occur. If the windings suffer any damage the high ground fault currents can lead to burning spots in the laminations. In order to ensure that no damage can occure, differential protection is strongly recommended. b) High-resistance earthing: As a rule, the limited currents arising during a phase short-circuit to earth endanger neither windings nor cables. As the neutral conductor’s earthing resistance is usually rated for short-time operation only, it is advisable to consider the installation of selective protection devices.
c) Non-earthed neutral connection This refers to a non-earthed network system, i.e. not only the alternator’s neutral point is unearthed, but the entire network is operated without neutral point earthing. The following section describes the effects on the alternator, not what happens within the network. In the event of a short-circuit to earth in an unearthed network, it is possible that a phase is shorted to earth for a long period of time. The winding insulation of the alternator measured to ground then is subjected to a voltage ingreased by factor √3. In accordance with German VDE 0530 – 1 standard this situation may not extend beyond a certain period. If it is anticipated that the machine is to be operated for longer periods under such conditions then the winding must be rated with a suitable (higher) insulation level.
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7. Parallel operation
7.1 General Parallel operation of a required number of gen-sets allows an optimum utilization and increased efficiency. Furthermore, the reliability of the system is improved because at breakdown of one gen-set the remaining sets will take the load, proper load management provided.
7.2 Conditions for parallel operation The alternators to be connected to the mains or operated in parallel must comply with the synchronisation conditions, i.e. they must be identical with regard to the following criteria: Voltage Frequency Phase sequence Phase angle Permissible tolerances prior to full-load connection are as follows: Voltage tolerance 5 % of UN Frequency tolerance 2 % of fN The frequency tolerance applies to conventional
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diesel-driven generating sets. A lower value is permissible where additional flywheels are used. In order to prevent synchronisation errors arising, for example due to the actions of unqualified operating personnel, it is advisable to install a synchronising relay in the switchgear which only releases the circuit breaker after the prescribed synchronising conditions have been met with. After paralling, the active and reactive load distribution must be balanced.
7.3 Start-up synchronisation for isolated parallel operation This function can only be used on machines of the same type and necessitates simultaneous starting of the diesel driven units. The alternators are electrically interconnected at standstill. As speed increases, the alternators are self-excited and attempt to synchronise with each other. In order that the equalizing currents which flow in the primary circuit
UVW until synchronisation is reached are not exceeding the rated current, the exciter current is to be limited when using an external voltage (12 V DC) for initial excitation. A blocking diode is used to connect the 12 V battery to the regulator. Apart from this, the regulator supply is to be interrupted in accordance with 6.2 “De-excitation” as the machine runs up to speed and released again after reaching the rated speed. The voltage subsequently applied to the regulator at terminals I1 - K1 rises above the battery voltage. A blocking diode in the battery supply lines prevents return flow to the battery, which can then be disconnected. 7.4 Stationary operation/ load distribution ●
Active load distribution is governed by the prime mover’s speed characteristic.
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Reactive-load distribution is governed by the alternator’s voltage characteristic.
The following methods of reactive-load distribution may be used: 7.4.1 Voltage droop The terminal voltage is lowered relative to the reactive current. The identical voltage droop is required for maintaining the reactiveload distribution in proportion to the output. The voltage droop’s cos phi relationship ensures that in parallel operation with the mains and when the mains voltage fluctuates any apparent change in output is kept to a minimum. This method can be used up to a mains-voltage fluctuation of ± 2 %. The voltage droop at nominal current is as follows: 0% 1.3 % 1.8 % 3%
at cos phi = 1 at cos phi = 0.9 at cos phi = 0.8 at cos phi = 0
Proven experience results in a factory setting for ensuring stable parallel operation of 3 % at nominal current and cos phi 0.1. For alignment purposes with other makes, the droop can be infinitely adjusted from 0 % - 6 % of the nominal voltage.
7.4.2 Power factor regulation This method is used for parallel operation with the mains where heavy voltage fluctuations occur. A cos phi regulator located in the alternator or the switchgear energises the alternator’s COSIMAT N+ regulator in order to maintain the pre-set power factor, i.e. the alternator voltage is automatically adjusted to the mains voltage.
7.5 Parallel mains operation Since in the majority of cases the mains has a much higher short-circuit capacity than the alternators, the number of units running in parallel is irrelevant so that no significant influence is exerted. As a result, almost all voltage fluctuations are determined by the mains. In the event of a mains voltage fluctuation of ∆U ≤ 2 % the voltage droop in accordance with 7.4.1 can be used. In the event of a mains voltage fluctuation of ∆U > 2 % a cos phi regulator is used which automatically adjusts the alternator voltage to the mains voltage by influencing the exciter voltage. This ensures that the pre-set power factor remains constant in the event of mains voltage fluctuations or if the alternator is subjected to various loads. If a certain power factor is required at the mains interface point, the current transformer effecting the cos phi regulator
must be located at this point. It is advisable to install an exciter current limiter in order to prevent the exciter circuit from being overloaded. It limits the exciter current to the value of the nominal power rating at cos phi = 0.8. It is further possible to influence the reactive power supply by using a reactive power regulator. Permissible increases in voltage and frequency fluctuations are stipulated by the applicable German standard DIN VDE 0530 - 1, Section 12.3, Figures 10 and 11. If voltage and frequency deviate from the nominal values, the temperature at constant nominal power will increase. This reduces the service life of the winding and as a result that of the overall machine. Voltage increases cause temperature rises in the iron of the main machine which are transmitted to the winding. Drops in voltage cause the current to rise and, as a result, the winding temperature in-
creases. Since the service life of the winding is always compromised if the temperature in the relevant temperature class is exceeded, it is advisable to prevent long operating periods at the extreme limit of the range A in German DIN VDE 0530 – 1. This will be ensured if the machine is built and operated in accordance to the operating data known during project stage. 7.6 Oscillations Periodic fluctuations in active and reactive load are caused by the irregular torque variations of internal combustion piston engines. In order to attenuate these fluctuations in parallel operation, a damper cage is installed in the alternator as standard.
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8. Features of the medium voltage winding
8.1 General AvK builds synchronous machines for the below listed nominal voltages and outputs:
of AvK alternators are in use by satisfied customers all over the world. They represent ample proof of the outstanding standard of AvK medium voltage technology in the field of brushless alternators.
Power range: 3,3 kV up to 13000 kVA 4,16 kV up to 16000 kVA 6,0 – 6,3 – 6,6 kV up to 18500 kVA 10,0 – 10,5 – 11,0 kV up to 26000 kVA 13,8 kV up to 27800 kVA 15,0 kV up to 20000 kVA Mainly synchronous generators are produced. Special voltages in the ranges between 3.3...15 kV can be realised by AvK upon request. The design and manufacture follows the applicable standards for electrical equipment. Special requirements will be considered upon request. In order to ensure that the highest degree of operating reliability is maintained under the most various operating conditions, insulating materials have been coordinated and developed over many years in conjunction with leading manufacturers in this area. Large numbers
8.2 Design and manufacture The systematically developed insulation structure, the manufacturing process and the materials used are described below. The basic material for the coils is profil copper wrapped in mica film. The coils made from this are shaped by expansion and trimming during installation in the stator slots. The insulation of the coil limbs – the area in which the stator slots are located – is carried out subsequently using temperature class “F”
high-grade thermosetting mica film. A tight winding around the coil ensures high-quality insulating properties. This insulating material consists of three components: ● glass fibre as the base material ● high-grade mica film as the insulating material ● epoxy resin as the binding agent. Coil-limb insulation thickness is determined by the nominal voltage. A special hardening press operating under high pressure at a temperature of between 160° C - 180° C is used to harden the coil limbs uniformly and give them their exact shape for installation in the stator slots. To ensure uniform coil production quality, they are monitored by measuring the loss factor in relation to the voltage. The test is carried out in accordance with German VDE 0530 – 1 standard. The initial- and rise-time values are far
Outer mica sleeve
Mica film Polyester film Profile copper
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below maximum permitted levels. Impulse voltage tests carried out on master coils monitor the strand insulation in accordance with German VDE 0530 -15, IEC 34 -15. Tests are subsequently carried out at regular intervals on the master coils, independent of any order specification. In addition to this, during these tests an impulse voltage test is carried out on the main insulation. Voltage tests according to the process instruction are carried out on the finished coils after they have been inserted into the stator. After interconnecting the coils to form a winding, each phase is subjected to a voltage test in accordance with German VDE 0530 - 1, IEC 34-1. Depending upon the nominal voltage, the coil heads are insulated by overlapping them with several layers of various integratedmica glass-fibre tapes.
9. Factory tests
For voltages greater than 4.16 kV, measured between phases, each coil limb is provided with coil-side corona shielding for the length of the laminated core, which prevents glow discharge and destruction of the coil-limb insulation within the laminated core. The coil-side corona shielding combines with overhung corona shielding, which uniformly reduces field strengths in the slot exit area towards the coil head in order to keep damaging field-strength fluctuations to an acceptable level. After having been wound completely, the stator undergoes heat treatment in accordance with the specifications of the insulatingmaterial manufacturers. The material then hardens and fuses together to form a non-porous, absolutely airtight insulating cover which is impervious to moisture. In order to maintain control over magnetic forces during sudden peak loads and, in
particular, in the event of short circuits, the coil heads have been mechanically fixed by means of suitably dimensioned fastening elements. ●
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The straight sections of the coil limbs protruding from the slots are mutually supported by inserted wedges, which are encapsulated in resin. Depending on their length and projection, the coil heads are bound together on the inclined section of the coil head projection by one or more so-called “polyester cords”. These polyester cords then harden during the previously mentioned stator’s heat treatment. In doing so, uniform shrinkage occurs so that the individual coil heads combine to form a single winding overhang of greater rigidity, yet more compact size. The geometrical design of a ring-type bonding made of insulating material on the winding overhang serves to ensure optimized rigidity of the winding overhang.
These measures combine to prevent any movement or indeed deformation of the winding overhang even with extreme loads during alternator operation.
9.1
9.2
Standard tests
Special tests (at extra charge)
1. Cold resistance measurements
1. No-load characteristic
2. Residual voltage measurement
2. Short-circuit characteristic
3. Voltage symmetry
3. Efficiency measurement (summation of losses method)
4. Phase-sequence test 5. Load characteristic with cos phi = 0.1
4. Temperature-rise test
6. Set-point potentiometer range/Voltage adjustment range
5. Noise-level test
7. Voltage regulator
7. Harmonic content analysis
7.1 Voltage regulator adjustment
6. Load connection and disconnection
8. Peak short-circuit test
7.2 Underspeed protection adjustment
9. Sustained short-circuit current measurement
7.3 Parallel operation adjustment
10. Vibration measurement (kardan driven or at motor operation)
8. Short time overload with cos phi = 0.1 or at short-circuit 9. Winding test
11. Rotor leakage test with rotor removed (inductor)
10. Overspeed test at 120 % nominal speed 11. High voltage measurement 12. Insulation resistance measurement 13. Adjustment of additional voltage regulator modules Final acceptance: General construction Inspection of component sizes, cable inspection, identification, circuit diagram, nominal data, space heater, temperature sensors etc.
Subject to technical modifications 23
AvK Deutschland GmbH & Co. KG Steinstraße 80 · D - 85051 Ingolstadt (Germany) P.O.B. 10 06 51 · D - 85006 Ingolstadt (Germany) Phone +49 8 41/7 92 - 0 · Fax +49 8 41/7 30 00 e-mail:
[email protected] Sales: Dreieich branch Benzstraße 47- 49 · D - 63303 Dreieich (Germany) P.O.B. 10 11 28 · D - 63265 Dreieich (Germany) Phone ISDN +49 61 03/50 39 - 0 · Fax +49 61 03/50 39 - 40 e-mail:
[email protected]
PB DIG 40498 GB
AvK Deutschland GmbH & Co. KG
