DG Sizing of Generator
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electrical...
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ELECTRICAL DESIGN PROCEDURES
BATTERY SIZING CALCULATIONS
DTPEGEN100600
ROLTA INDIA LIMITED
EDS ELECTRICAL DESIGN PROCEDURES DG Sizing Calculations Calculations DTPEGEN100600 Revision History Revision Level
Revision Date
Revision Description
Department Head (Approver)
This Document and all contained herein are proprietary of ROLTA INDIA LIMITED and is subjected to confidentiality restrictions
between ROTLA INDIA LIMITED and the Recipient. Copyright Reserved.
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ELECTRICAL DESIGN PROCEDURES
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Subject
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Page no
8. EMPIRICAL FACTORS USED IN SIZING FOR MOTOR LOADS.................................................7 9. LOAD ANALYSIS...........................................................................................................................9 12 REQUIRED CALCULATION INPUTS:.......................................................................................15 13 REQUIRED CALCULATION OUTPUTS:...................................................................................15
1. Purpose & Scope DG sets are used under the following conditions: 1. As a primary source of power a. Supplying isolated loads in the rural areas b. Supplying essential loads in power / industrial / chemical plants. 2. As a backup to the main or grid supply a. DG set operating in parallel with the grid b. DG set sunning in isolation from grid supply for meeting the deficit or for some critical loads. © Copyright 2008. Rolta India Limited. All Rights Reserved.
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This design guide for Diesel – Generator Set (DG SET) covers the following aspects. • Standard DG ratings and voltage levels • Sizing of DG set • Parallel operation with the grid Neutral earthing
2. Applicability This procedure is applicable to all projects. 3. References ASME B15.1
Safety Standard for Mechanical Power Transmission Apparatus
ASME B31.1
Power Piping Code
IEEE 80
Guide for Safety in Substation Grounding
IEEE 112
Standard Test Procedure for Polyphase Induction Motors and Generators
IEEE 115
Test Procedure for Synchronous Machines
IEEE 43
Recommended Practice for Testing Insulation Resistance of Rotating Machinery
IEEE 1050
Guide for Instrumentation and Control Equipment Grounding in Generating Stations
NEMA 250
Enclosures for Electrical Equipment (1000 Volts Maximum)
NEMA AB 1
Molded Case Circuit Breakers and Molded Case Switches
NEMA ICS1
Industrial Controls and Systems
NEMA ICS2
Industrial Control Devices, Controllers, and Assemblies
NEMA ICS6
Enclosures for Industrial Controls and Systems
NEMA MG1
Motors and Generators (Including Rev. 1 and 2)
NEMA MG2
Safety Standard for Construction and Guide for Selection, Installation, and Use of Electric Motors and Generators
4.0 DG Set Ratings & Voltages :
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DG sets upto 1000 KVA are rated for 415V and those above 1000 KVA are rated for 3.3 / 6.6 / 11 KV as per the requirement of primary distribution voltage in the plant. Some of the typical ratings available in India are as follows : 415V : 10 / 25 / 50 / 75 / 100 / 125 / 150 / 200 / 250 / 300 / 400 / 500 / 650 / 750 /
800 / 1000 KVA
3.3/6.6/11 KV : 1460 / 2200 / 3000 / 5000 / 6500 / 8000 / 12000 KVA 5.0 Diesel Engine Speeds :
Diesel engine speed is normally classified into following three categories : 1. High Speed (above 750 RPM) 2. Medium Speed (above 300 RPM and upto 750 RPM) 3. Low Speed (upto 300 RPM) When DG sets are used for continuous duty i.e. more than 6000 hours per year, it is recommended that engine of either low speed or medium speed are selected for getting high service life. DG sets used for emergency purpose can be of high speed type. The above considerations are true only for the conventional loads like pump / fan motors, heaters, lighting etc. However sizing of DG for feeding nonconventional loads like Arc Furnace and Rolling Mills is very complex and not considered here. 6. DEFINATIONS: 1.1.1
System Performance The power generating system shall conform to the following performance requirements:
1.1.1.1
Rating Engine continuous horsepower shall be sufficient to deliver full rated generator set kW/kVA when operated at rated rpm and equipped with all enginemounted auxiliary loads.
1.1.1.2
Start Time and Load Acceptance Upon receiving a start signal, the standby diesel generator shall be capable of starting automatically without local attendance, reaching synchronous speed and rated voltage and frequency within 10 sec and be ready to accept load to its rated capacity under at normal operating temperature, in accordance with NFPA 110. The unit shall be capable of three consecutive starts without recharging. The standby diesel generator set shall be capable of either manual or automatic start and, in either case, check synchronization, automatically synchronize and close to either a live or dead bus.
1.1.1.3
Frequency regulation Engine generator operation shall be isochronous, regulated to within the rated frequency ±0.25 % from no load to full load. © Copyright 2008. Rolta India Limited. All Rights Reserved.
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ELECTRICAL DESIGN PROCEDURES 1.1.1.4
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Voltage regulation Generator terminal voltage shall be maintained at rated voltage ±0.5% for any steady state load between no load and full load.
1.1.1.5
No load operation It is required that the standby diesel generator be capable of operating at full speed, no load, for one hour.
1.1.1.6
Transient Operation When loaded in accordance with the above requirements, the transient voltage drop shall be limited such that the generator voltage is not less than 80 percent of nominal voltage, and frequency is not less than 95 percent of nominal. In addition, the voltage at the generator shall recover to within 90 percent of nominal voltage and the frequency to 98 percent of nominal within 2 sec after load application. During recovery from transients caused by load application, or resulting from 100 percent load rejection, the speed of the generator set shall not exceed nominal speed plus 75 percent of the difference between nominal speed and the overspeed trip set point or 115 percent of nominal, whichever is lower.
1.1.1.7
Load Banks Properly sized threephase load bank, including associated switching equipment, shall be provided for use during periodic exercising of the diesel generator.
7. GENERATOR LOADING: Type of Electrical Load Loads vary according to applications and it is useful to examine and classify their characteristics as follows: Passive Loads Include heating, lighting and domestic type loads. Easily evaluated. Usually expressed in kW on assumption of unity P.F. In sizing generating sets passive loads are usually treated as constant at the specified kW. Cage Induction Motors The most common type of industrial load characterized by a high initial starting kVA at low P.F. and a fairly high peak kW during runup. Motor output usually expressed in kW so that:
F.L. input kW
=
Rated kW output Per Unit F.L. efficiency
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ELECTRICAL DESIGN PROCEDURES and F.L. kVA
input =
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DTPEGEN100600
F.L. input kW
F.L. power factor If the motor output is expressed in HP:
F.L. input kW
=
0.746 X Rated HP Output Per Unit F.L. efficiency
Columns (1) to (6) of Fig. 1 list typical full load performance figures for induction motors from 1.1 to 1000kW output. The method used for starting squirrel cage motors is most important. The simplest method id D.O.L. (directonline) starting at full voltage and a typical motor would drawn an initial starting kVA of about 6.5 times the full load value, and a possible peak input kW during runup of about 3.25 times full load value. A motor supplied from a generating set and started in this way would probably produce serious transient voltage dip problems and might, under some conditions, require an oversize engine to power the runup. To reduce the demand on the supply during starting, cage motors frequently use different forms of reduced voltage starting, the two most common being startdelta and autotransformer starting. Both the initial kVA and the peak kW are substantially reduced but the motor develops reduced torque, which prolongs the run up time. Columns (7) to (12) of Fig. 1 show initial start kVA and peak input kW for typical cage. motors with three methods of starting, D.O.L., autotransformer with 75% tap and startdelta. Slip ring Induction Motors Used where high starting torque is required with a moderate starting current. Starting involves full voltage applied to stator and series rotor resistance which is progressively cut out during run up. Starting kVA is typically between 1.25 and 2.0 times rated input and starting power factor is high, typically 0.9 so that generating set sizing considerations usually centre on engine power rather than transient voltage dip. Columns (13) to (18) of Fig.1 show the kVA and kW input to slip ring motors during starting for three starter settings 1.25, 1.5 and 2.0 times full load input. Rated load input is as for cage. motors and can be taken from columns (1) to (6).
Rectifier and Similar NonLinear Loads Rectifier and thyristor type loads draw a current which is high in harmonics and when the supply is obtained from a generating set the consequence distortion of the alternator voltage wave may be sufficient to affect the operation of other equipment running from the same supply. Generator temperature and © Copyright 2008. Rolta India Limited. All Rights Reserved.
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ELECTRICAL DESIGN PROCEDURES
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voltage control instability may also occur. Because of this, generators supplying nonlinear loads should be generously rated so that the kVA rating should be at least twice the full load kVA input to the rectifier or thyristor.
Regenerative Loads Cranes and hoists sometimes use electrical regeneration as a means of braking. The effect of returning power to a generating set is to reduce the engine power requirement and produce an increase in speed. Small levels of regeneration will be absorbed in the losses of the set but if it becomes appreciable, the speed may rise to an unacceptable extent since the governor can have no effect in limiting the speed under such conditions. To guard against this the net regenerated power should not exceed 20% to 25% of the generating set kW rating, the lower figure for sets above 200 kW, the larger figure for small sets of say 20 kW rating. If this cannot be achieved then a ballast load should be connected across the generator (activated by a reverse power relay) intermittently rated but capable of absorbing the maximum regenerated kW’s.
Capacitive Loads Although not normally a factor in sizing generating sets, mention should be made of the effect of capacitive loads on generating sets. Such loads may result in an overall leading power factor condition which tends to self excite the generator and in extreme cases may lead to excess terminal voltage which the AVR cannot control. Special consideration must therefore be given to such cases.
8. EMPIRICAL FACTORS USED IN SIZING FOR MOTOR LOADS 8.1“K” FACTOR In the absence of Vendor Data the starting kVA for an induction motor may be estimated by the application of the “K” factor to the full load kVA as shown in Fig.1. Thus:a. Initial starting kVA – F.L. kVA x K For cage motors K will depend on the design of the motor and the method of starting. For D.O.L. starting, K may vary between 5.0 and 7.5 a typical average value being 6.5 which may be used in the absence of an actual figure. If reduced voltage starting is used then the K value will be reduced as the square of the voltage so that:b.K for reduced voltage start = K for D.O.L. x V2 c. (where V is the reduced start voltage in P.U. of normal volts). Thus for typical cage motors:
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ELECTRICAL DESIGN PROCEDURES
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Starting Method
Applied Voltage
K Factor
D.O.L.
1.0
6.5
Startdelta
0.58
2.2
Autotransformer (60% tap)
0.60
2.3
Autotransformer (75% tap)
0.75
3.6
DTPEGEN100600
For slip ring motors the starting kVA is restricted by the external starter resistance in the rotor are usually determined by the starting torque requirements of the load. a. A typical valve would lie between 1.25 and 2.0, but the Motor Vendor must advise.
8.2 "E" FACTOR In starting a squirrel cage motor energy is required to accelerate the rotor and its coupled load from standstill to normal running speed. If the load inertia is small, acceleration will be fast and only a small amount of energy will be required, but for high inertia loads, acceleration will be prolonged and energy input correspondingly increase. The peak input kW is however the same. Reduced voltage starting methods will reduce the power input during starting but will prolong the run up time so that energy input for a given load inertia will be the same for all methods of starting including D.O.L. For lightly loaded motors and low inertia type loads the energy required during run up will be small and a significant proportion could be contributed from the kinetic energy of the generating set rotating parts assuming of course that the load on the generating set is sufficient to cause a significant drop in speed. This means that under these conditions a satisfactory motor start can be made even though the peak kW input to the motor is higher than the rated maximum output of the set. However, for high inertia loads the kinetic energy available from the generating set would be too low to be a worthwhile contribution to the total energy required to run the motor and its load up to speed and in these cases all the power must be supplied from the engine which must therefore have sufficient peak load capability. It can be shown that the peak kW input to a squirrel cage motor during run up is approximately half the initial starting kVA and this can therefore be used to determine the engine power requirement for high inertia loads. All cases can be estimated by the use of an empirical “E” factor so that:
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ELECTRICAL DESIGN PROCEDURES Effective peak kW
BATTERY SIZING CALCULATIONS =
Start kVA x E
=
FLkVA x K x E
DTPEGEN100600
a. The value given to E will depend on the application and particularly the motor load inertia. For squirrel cage motors the maximum value will be 0.5 and other values can be found with the aid of Fig.2. For slip ring motors maximum kW occurs at the instance of starting and to allow for the high starting power factor a value of 0.9 should be assigned to E for this class of machine. The same value can be used for squirrel cage motors using special “soft start” techniques. where the run of characteristics obtained from thyristor controls is not unlike that of a slip ring motor. 9.
LOAD ANALYSIS
Figure 3 shows a tabulation, which is the analysis of a load comprising a number of separate elements. At the top of the sheet the load elements are itemised in the order in which they will be applied to the generating set. In the absence of other data the first item should be any passive load such as heating or lighting followed by the dynamic loads (i.e. motors) starting with the machine which imposes the largest starting load and working down in descending order. This is only a general rule and some rearrangement of order may prove advantageous after completing the first assessment. The next lower section of the load analysis table lists the demand on the set as the successive load elements are added. At each application the initial kW is shown, the effective peak kW during run up of the motor and the final kW after the load element is up to speed and running at its stated load. The sequence is repeated until all the elements have been added as shown for the sample installation in Fig. 3. At the bottom of the table are shown three key figures which will be used to determine the recommended plant. Maximum Total Peak kW This is the highest value in line reference 8 of the table and represents the maximum load the engine must handle during the process of connecting the load elements. Maximum Final kW This is the final figure in line reference 9 of the table and is the expected total load when all the load is connected and running at stated value. Normally this figure would represent the plant kW rating.
Maximum Starting kVA This is the highest value in line reference 6 and is the highest suddenly applied kVA increment which the alternator will experience. It must therefore be used to determine the alternator size in relation to transient voltage dip limits.
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After analysing the load as described above it is worth checking to see whether a different sequence of applying the load elements would be beneficial. Clearly it cannot affect the final kW but it could result in a lower maximum total peak kW which frequently determines engine size.
10. Sizing the Set The Engine The engine must meet two requirements. First it must be able to supply all the connected load elements operating at their individual ratings for the required duration. Thus the “final kW” in Figure 3 must not exceed the rating of the set, continuous or standby as appropriate. The second requirement is that the engine must be able to develop sufficient power to meet the “maximum total peak kW” also evaluated in Fig.8. If this is only slightly higher than the plant rating determined above then it may make use of any engine short term reserve power which may be available (such as the ten percent overload capacity for continuously rated sets). In many cases however, it will be substantially greater in which case it will become the deciding factor in choosing the engine. The special, but not uncommon, case of a generating set powering only a single large motor often results in an engine peak power requirement out of all proportion to its continuous power rating. Since no other loads are involved effective economy can sometimes be made using the frequency tied start method in which the load motor and the generating set are run up together. The generating set controls for this, although not complicated are not standard and would only be justified for the larger sets where the special engineering costs could be absorbed. The Generator
The generator must have a continuous (or standby if appropriate) rating comparable with the “final kW” figure used in engine sizing. The load power factor is almost always taken to be 0.8 PF lagging but very occasionally a different operating power factor may be specified and this must be taken into account when choosing the generator. A further requirement is that the generator must be able to handle the largest step kVA load without excessive voltage dip which, in the absence of a prescribed figure should be taken as about 25 percent with 30 percent as an absolute maximum. The three factors which determine transient voltage dip are:a. Alternator reactance b.Load impedance c. Load power factor Considering a simple circuit comprising a generator represented by a voltage source and inductive reactance (generator transient reactance) in series with the load impedance. The simple generator is assumed to develop 1.0 Pu. volts at the terminals before the load switch is closed. On closing the switch a current flows, limited by the load impedance and the generator reactance in series so that part of the original 1.0 Pu volts is now dropped across the generator reactance leaving a reduced voltage at the machine terminals.
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ELECTRICAL DESIGN PROCEDURES Let:
BATTERY SIZING CALCULATIONS
E
=
Generated emf (= 1.0 Pu)
VT
=
Voltage at machine terminals
X
=
Pu transient reactance of generator
ZL
=
Pu. load impedance comprising in series
XL
= Pu load reactance
RL
= Pu load reactance
=
Generator kVA x SIN (COS–1 ∅)
XL
DTPEGEN100600
Step kVA Load RL
=
Generator kVA x COS ∅ Step kVA load
Total impedance
circuit
Z = ZL + X (added vectorially) = RL + j (XL + X) = √R2L + (XL + X)2.Pu Circuit prior to connecting transient load I = E = 1.Pu ZZ Generator terminal voltage on connecting transient load, VT = IZL.Pu
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ELECTRICAL DESIGN PROCEDURES Transient Dip,
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Voltage
= E – VT = 1 – VT.Pu The accurate estimate of running load of DG set can be made considering individual motor rating , efficiency and power factor. KVA =
P * LF PF * η * DF
Where, KVA =
Minimum DG capacity
P
=
Connected KW on DG
DF
=
Diversity Factor (>=1.0).
=
Sum of Individual Max. Demands
Max. Demand on Power Station
The diversity factor is always greater than 1. If it is not available the same can be assumed as 1.
LF
=
Load Factor (0.6 to 0.9) Maximum real power consumed
=
maximum real power that would be consumed
11.0 Performance of Generating Sets Between the required maintenance intervals and under the site ambient conditions. Generating set power outputs are defined in the Codes by one of the following: Continuous Power This is the power that a generating set is capable of delivering © Copyright 2008. Rolta India Limited. All Rights Reserved.
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continuously for an unlimited number of hours. Prime Power This the maximum power available during a variable power sequence which may be run for an unlimited number of hours per year and is the valve normally equal or greater than the calculated emergency or standby loads. The permissable average power during a 24 hour period shall not exceed a percentage, declared by the supplier, of the Prime Power. Limited Time Running Power This is the maximum power that a generating set is capable of delivering for up to 5000 hours per year of which a maximum of 300 hours is continuous. It is accepted that operation at this rating will affect the life of the set. Engine Governing Performance Governors function by detecting a speed change and then automatically adjusting the fuel supply to restore the speed to normal. This means that except where load anticipatory devices are used, governor operation must be preceded by an actual speed change and for a large load change this speed change will usually be considerable. BS7698, 4, recognizes several standards of diesel engine governing, class G1 normally being chosen for generating set applications. Governing performance can be defined by four factors: Steady State Speed Band Total variation of speed under fixed load condition. For G1 governing, 1.0 percent for less than 25 percent load, 0.8 percent for higher values. Transient Speed Variation Maximum deviation of speed following sudden load change measured from mean steady state speed band before load change. For G1 governing, 10 percent for 100 percent load removal, 10 percent for application of a stipulated load which is 100 percent for naturally aspirated engines and a lesser figure for pressure charged engines depending on the engine power (60 percent would be typical for many engines). Recovery Time Measured from the point where speed departs from the initial steady state speed band to the point when the speed returns to and © Copyright 2008. Rolta India Limited. All Rights Reserved.
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remains within the new steady state speed band. For G1 governing 8 seconds maximum for the load changes defined for transient speed variation limits.
Speed Droop Speed change between zero and rated load. For G1 governing, 5 percent of rated speed. Alternator Voltage Control Characteristics The electrical load on a generating set is usually fluctuating, sometimes over wide variations and to maintain a substantially constant output voltage an automatic, fast acting regulating system must be used. In modern brushless alternators this is achieved by the use of a solid state AVR (automatic voltage regulator) which adjusts the exciter field current to compensate for load, speed and temperature changes. As in the case of the engine speed governor, a voltage change must occur before AVR action is initiated and a measurable time elapse before the corrective process is complete. BS.4999, part 40 (and other International Standards) cover voltage regulation and recognizes several different grades. Grade VR2.23 is normally chosen for general purpose use in generating sets. Voltage regulation performance can be defined by three factors. Steady State Limits Limits between which the terminal voltage will lie for any fixed load between no load and rated load at rated power factor. For Grade VR2.23 steady state limits are ±2.5 percent but limits of ±2.0 percent or even ±1.0 percent are frequently specified for special application. Transient Limits Initial voltage change immediately following the sudden application of a specified low power factor load or the sudden removal of rated load. For Grade VR2.23 the figure is 15 percent voltage dip for application of 60 percent rated kVA at 0. To 0.4 lagging and 26 percent overshoot for removal of rated load at 0.8 p.f. (Different transient limits are frequently specified for the application of specified loads such as starting of motors). Recovery Time Time between point of sudden load application and the point at which the voltage returns to 97 percent of rated voltage. For Grade VR2.23 maximum recovery time for load application specified in (b) above is 0.5 second.
Influence of Alternator Reactance on Transient Performance Transient reactance of generators is effective whenever load changes occur. On applying a sudden load it behaves as a series reactance, absorbing some of the generated voltage and © Copyright 2008. Rolta India Limited. All Rights Reserved.
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causing the temporary voltage dip at the alternator terminals. Transient reactance is usually expressed in per unit terms (although sometimes percentage) related to the rated load impedance. Thus a 0.25 Pu (or 25 percent) transient reactance would be numerically equal to a quarter of the impedance of the rated load circuit. Since transient reactance is purely reactive whereas the load impedance usually comprises both resistance and reactance it follows that the effect of transient reactance on voltage dip will depend on the load power factor and zero power factor lagging will produce the greatest transient voltage dip for a given load current. 12
REQUIRED CALCULATION INPUTS:
The following is a summary of the required inputs to the calculation to satisfy this procedure:a. Generator Bus Design Loading kW and KVAR (Motor) kW and KVAR (Non Motor) b.Profile for Load Changes c. Permitted limits for voltage and frequency under steady state and transient conditions.
13
REQUIRED CALCULATION OUTPUTS:
Size of engine and generator required to meet all possible combination of load conditions while remaining within the voltage and frequency limits.
FIG.1 – PERFORMANCE OF TYPICAL INDUCTION MOTORS
Maximum Input during starting and Runup Rated
Typical
Cage Motors
Slip Ring Motors
Output
Full Load Performance
(E = 0.5)
(E = 0.9)
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ELECTRICAL DESIGN PROCEDURES
kW
Appro x HP
P.F .
P.U. Eff
BATTERY SIZING CALCULATIONS Inpu t
Inpu t
kVA
kW
D.O.L. K = 6.5
DTPEGEN100600
Auto Transfor
StartDelta
K = 3.6
K = 2.2
K = 1.25
K = 1.5
kVA
kW
kVA
kW
kVA
kW
kVA
kW
kVA
kW
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
1.1
1.5
0.8 1
0.75
1.81
1.47
11.8
5.88
6.52
3.26
3.98
1.99
2.26
2.04
2.72
2.44
3
4
0.8 3
0.81
4.46
3.70
30
15
16.1
8.03
9.81
4.91
5.58
5.02
6.69
6.02
7.5
10
0.8 3
0.85
10.6
8.82
68.9
34.5
38.2
19.1
23.3
11.7
13.2
11.9
15.9
14.3
15
20
0.8 2
0.885
20.7
16.9
135
67.3
74.5
37.3
45.5
22.8
25.9
23.3
31.1
27.9
30
40
0.8 2
0.905
40.4
33.1
263
131
145
72.7
88.9
44.4
50.5
45.5
60.6
54.5
50
67
0.8 3
0.925
65.1
54.1
423
212
234
117
143
71.6
81.4
73.2
97.6
87.9
80
107
0.8 5
0.935
101
85.6
656
328
364
182
222
111
126
114
151
136
100
134
0.8 5
0.94
125
106
812
406
450
225
275
137
156
141
187
169
125
167
0.8 5
0.942
156
133
1014
507
562
281
343
172
195
175
234
211
150
200
0.8 6
0.945
185
159
1202
601
666
333
407
203
231
208
277
250
170
228
0.8 6
0.945
209
180
1358
679
752
376
460
230
261
235
313
282
200
268
0.8 6
0.945
246
212
1599
800
886
443
541
271
307
277
369
332
250
335
0.8 6
0.945
308
265
2002
1001
1109
554
678
339
385
346
462
416
300
400
0.8 5
0.945
373
317
2424
1212
1343
671
821
410
466
420
559
504
400
536
0.8 5
0.945
498
423
3237
1618
1793
896
1096
548
622
560
747
672
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ELECTRICAL DESIGN PROCEDURES
BATTERY SIZING CALCULATIONS
DTPEGEN100600
500
670
0.8 4
0.945
630
529
4095
2047
2268
1134
1386
693
787
709
945
850
600
804
0.8 4
0.945
756
635
4914
2457
2722
1361
1663
832
945
850
1134
1021
800
1070
0.8 3
0.945
1020
847
6630
3315
3672
1836
2244
1122
1275
1147
1530
1377
1000
1340
0.8 2
0.945
1290
1058
8385
4192
4644
2322
2838
1419
1612
1451
1935
1741
.50
(a)
.45 (b)
.40
(c) .35
10
20
© Copyright 2008. Rolta India Limited. All Rights Reserved.
50
100
200
Issue Date: Uncontrolled When Reproduced
500
Page 17 of 21
ELECTRICAL DESIGN PROCEDURES
BATTERY SIZING CALCULATIONS
Description of Load Elements
Rated kW
DTPEGEN100600
Input kW
Input kVA
K
50
50

A
Lighting and Heating
B
SR Motor – Crusher – 2 x FLC Start
250
265
308
2.0
C
SC Motor – Unloaded Compressor – Auto transf. 75% Top
200
212`
246
3.6
D
SC Motor – Pump – DOL Start
7.5
8.8
10.6
6.5
E
SC Motor – Fan – Y∆ Start
15
16.9
20.7
2.2
F
SC Motor – Fan – DOL Start )
3.0
3.7
4.5
6.5
)
) Started together
G H
Load Elements Line Ref
A
B
C
D
(1)
0
50
315
527
F.L. kW
(2)
50
265
212
F.L. kVA
(3)
50
308
Load
Start K Factor
(4)

Element
Start E Factor
(5)
Start kVA Eff Peak kW
E
F
8.8
16.9
3.7
246
10.6
20.7
4.5
2.0
3.6
6.5
2.2
6.5

0.9
0.38
0.45
0.45
0.4 5
(6) = (3) x (4)
50
616
886
69
46
29
(7) = (5) x (6)
50
554
336
31
20
13
Total Effective Peak kW
(8) = (1) + (7)
50
604
651
591
Final kW
(9) = (1) + (2)
50
315
52.7
556
Initial kW
Applied
Max value of Total Eff. Peak kW (max value of line ref 8)
651
Max value of Final kW (max value of line ref 9)
556
© Copyright 2008. Rolta India Limited. All Rights Reserved.
Sizing Recommendation Cummins KTA 3891
Issue Date: Uncontrolled When Reproduced
Page 18 of 21
G
H
ELECTRICAL DESIGN PROCEDURES
BATTERY SIZING CALCULATIONS
Max value of Start kVA (max value of line ref 6)
886
DTPEGEN100600
577 kW Cont/635 kW O/L with V/H2 AVR functions to handle 651 kW peak.
Rating Class
Cont
K1
°C ambient
30°C
M.ASL
1000
K2
952
Service HZ
Alt temp rise
100°C (F)
K3
1.0
Equiv. kVA
529
Max % V.Dip
Alt Equiv cont kW
14.
1.0
Alt Wdg type
A
.
Service Volts
380 50
Max
start
982
L Low Reactance Alternator Frame E7B Cont kW = 620 Start kVA for 20% dip = 1023
Transient
20
NEUTRAL EARTHING :
DG sets upto 500 KVA solidly earth system is recommended. The earthing is provided so as to minimise the damage to stator winding in the event of an earth fault. If DG is envisaged to operate in parallel with the grid, it is recommended to provide solidly earth system irrespective of KVA rating. In case of isolated operation of DG set, for rating above 500 KVA, resistance earthing is considered for limiting the earth fault current to maximum full load current of the DG set. DG sets of 3.3 / 6.6 / 11 KV are always provided with resistance grounded system. The earth fault current is limited to maximum full load current of the DG set. The value of neutral resistor is given by R = VL √3 * IL Where, VL = Line to Line RMS voltage in Volts IL = Rated Current in Amps © Copyright 2008. Rolta India Limited. All Rights Reserved.
Issue Date: Uncontrolled When Reproduced
Page 19 of 21
T S G S
ELECTRICAL DESIGN PROCEDURES R
BATTERY SIZING CALCULATIONS
DTPEGEN100600
= Resistor value in Ohms
© Copyright 2008. Rolta India Limited. All Rights Reserved.
Issue Date: Uncontrolled When Reproduced
Page 20 of 21
ELECTRICAL DESIGN PROCEDURES
© Copyright 2008. Rolta India Limited. All Rights Reserved.
BATTERY SIZING CALCULATIONS
Issue Date: Uncontrolled When Reproduced
DTPEGEN100600
Page 21 of 21
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