Economical Voltage for Power
Transmission:
§ Economic
generation voltage is generally limited to following values (CBIP Manual).
Economic generation voltage (CBIP Manual)
|
|
Total Load
|
Economical Voltage
|
Up to 750 KVA
|
415 V
|
750 KVA to 2500 KVA
|
3.3 KV
|
2500 KVA to 5000 KVA
|
6.6 KV
|
Above 5000 KVA
|
11 KV or Higher
|
§ Generally
terminal voltage of large generators is 11 kV in India. Step up voltage depends
upon Length of transmission line for interconnection with the power system and
Power to be transmitted.
§ High voltage
increases cost of insulation and support structures for increased clearance for
air insulation but decreases size and hence Cost of conductors and line losses.
§ Many
empirical relations have been evolved to approximately determine economic
voltages for power evacuation. An important component in transmission lines is
labor costs which are country specific.
§ An empirical
relation is given below.
§ Voltage in kV (line to line)
= 5.5x√0.62L + kVA/150
§ where kVA is
total power to be transmitted;
§ L is length
of transmission line in km.
§ American
practice for economic line to line voltage kV (based on empirical formulation)
is
§ Voltage in kV line to line =
5.5x√0.62L + 3P/100
§ For the
purpose of standardization in India transmission lines may be classified for
operating at 66 kV and above. 33 kV is sub transmission, 11 kV and below may be
classified as distribution.
§ Higher
voltage system is used for transmitting higher amounts of power and longer
lengths and its protection is important for power system security and requires
complex relay systems.
Required Power Transfer (MW)
|
Distance (KM)
|
Economical Voltage Level (KM)
|
3500
|
500
|
765
|
500
|
400
|
400
|
120
|
150
|
220
|
80
|
50
|
132
|
Factor affected on Voltage Level of system:
§ Power
carrying capability of transmission lines increases roughly as the square of
the voltage. Accordingly disconnection of higher voltage class equipment from
bus bars get increasingly less desirable with increase in voltage levels.
§ High
structures are not desirable in earthquake prone areas. Therefore in order to
obtain lower structures and facilitate maintenance it is important to design
such sub-stations preferably with not more than two levels of bus bars.
Size of
Cable according to Short circuit (for 11kV,3.3kV only)
§ Short
circuit verification is performed by using following formula:
§ Cross Section area of Cable
(mm2)S = I x√t / K
§ Where:
§ t = fault
duration (S)
§ I = effective
short circuit current (kA)
§ K = 0.094
for aluminum conductor insulated with XLPE
§ Example: Fault duration(t)=
0.25sec,Fault Current (I) = 26.24 kA
§ Cross
Section area of Cable =
26.24 x √ (0.25) / 0.094= 139.6 sq. mm
§ The selected
cross sectional area is 185
sq. mm.
Ground Clearance:
§ Ground Clearance in Meter =
5.812 + 0.305 X K
§ Where K=
(Volt-33) / 33
Voltage
Level
|
Ground
Clearance
|
<=33KV
|
5.2
Meter
|
66KV
|
5.49 Meter
|
132KV
|
6.10 Meter
|
220KV
|
7.0
Meter
|
400KV
|
8.84
Meter
|
Voltage Rise in Transformers
due to Capacitor Bank:
§ The voltage
drop and rise on the power line and drop in the transformers. Every transformer
will also experience a voltage rise from generating source to the capacitors.
This rise is independent of load or power factor and may be determined as
follows:
§ % Voltage Rise in
Transformer=(Kvar / Kva)x Z
§ Kvar
=Applied Kvar
§ Kva = Kva of
the transformer
§ z =
Transformer Reactance in %
§ Example: 300 Kvar bank given to 1200 KVA transformer with 5.75% reactance.
§ % Voltage
Rise in Transformer=(300/1200)x 5.75 =1.43%
Thumb Rule-11
Size of Cable on Secondary Side of Transformer (11KV/433V)
|
||||
Ref: KSEI Handbook
|
||||
Rating of T/C (KVA)
|
Primary
current (Amp)
|
Secondary
Current (Amp)
|
Min. Size
of Neutral Earthing Conductor (mm2)
|
Minimum
Size of Cable (mm2)
|
63
|
3.3
|
84
|
25X3
|
50mm2
|
100
|
5.25
|
133.3
|
25X3
|
95mm2 or
(2×50 mm2)
|
160
|
8.4
|
213.3
|
25X3
|
185mm2 or
(2×95 mm2)
|
200
|
10.49
|
266.6
|
25X3
|
300mm2 or
(2×120 mm2)
|
250
|
13.12
|
333
|
25X3
|
2×185 mm2
|
315
|
16.53
|
420
|
31X3 or
25X4
|
(2×300
mm2) or (3×185 mm2)
|
400
|
21.80
|
533
|
38X3
|
(3×300
mm2) or (2×400 mm2)
|
500
|
26.20
|
666.5
|
25X6
|
(3×400
mm2) or (4×240 mm2)
|
630
|
33
|
840
|
31X6
|
4×400 mm2
|
750
|
39.36
|
1000
|
50X4
|
Bus Bar
Trucking (min. Isc 50KA)
|
1000
|
52.50
|
1333
|
210mm2
|
Bus Bar
Trucking (min. Isc 50KA)
|
1250
|
65.50
|
1667
|
290mm2
|
Bus Bar
Trucking (min. Isc 50KA)
|
1600
|
83.98
|
2133
|
380mm2
|
Bus Bar
Trucking (min. Isc 50KA)
|
2000
|
105.00
|
2666
|
450mm2
|
Bus Bar
Trucking (min. Isc 50KA)
|
HT Fuse on Primary Side of Transformer (11KV/433V)
|
||||
Rating of T/C (KVA)
|
Primary
current (Amp)
|
Secondary
Current (Amp)
|
HT Fuse
|
|
Min (Amp)
|
Max(Amp)
|
|||
63
|
3.3
|
84
|
10
|
16
|
100
|
5.25
|
133.3
|
16
|
25
|
160
|
8.4
|
213.3
|
16
|
40
|
200
|
10.49
|
266.6
|
25
|
40
|
250
|
13.12
|
333
|
32
|
40
|
315
|
16.53
|
420
|
40
|
63
|
400
|
21.80
|
533
|
40
|
63
|
500
|
26.20
|
666.5
|
50
|
100
|
630
|
33
|
840
|
63
|
100
|
750
|
39.36
|
1000
|
75
|
160
|
1000
|
52.50
|
1333
|
100
|
160
|
1250
|
65.50
|
1667
|
100
|
200
|
1600
|
83.98
|
2133
|
160
|
250
|
2000
|
105.00
|
2666
|
200
|
250
|
Capacitor Bank for Power Supply Voltage
|
|
System Voltage
|
Minimum
rating of capacitor bank
|
3.3 KV ,
6.6KV
|
75 Kvar
|
11 KV
|
200 Kvar
|
22 KV
|
400 Kvar
|
33 KV
|
600 Kvar
|
Capacities of PVC conduits
|
||||
Nominal conductor Size mm
|
16 mm
|
20 mm
|
25 mm
|
32 mm
|
Number of
Cables (maximum)
|
||||
1.0
|
6
|
5
|
19
|
30
|
1.5
|
5
|
4
|
15
|
24
|
2.5
|
3
|
3
|
11
|
17
|
4
|
2
|
2
|
8
|
13
|
6
|
2
|
–
|
6
|
10
|
10
|
–
|
–
|
4
|
6
|
16
|
–
|
–
|
3
|
4
|
25
|
–
|
–
|
2
|
3
|
35
|
–
|
–
|
–
|
2
|
System Highest and Lower Voltage
|
||
Ref: NEC(India) :2011
|
||
System
Voltage
|
Highest
Voltage
|
Lowest
Voltage
|
240 V
|
264 V
|
216 V
|
415 V
|
457 V
|
374 V
|
3.3 kV
|
3.6 kV
|
3.0 kV
|
6.6 kV
|
7.2 kV
|
6.0 kV
|
11 kV
|
12 kV
|
10 kV
|
22 kV
|
24 kV
|
20 kV
|
33 kV
|
36 kV
|
30 kV
|
66 kV
|
72.5 kV
|
60 kV
|
66 kV
|
72.5 kV
|
60 kV
|
132 kV
|
145 kV
|
120 kV
|
220
|
kV 245 kV
|
200 kV
|
400 kV
|
420 kV
|
380 kV
|
Number of Points for Dwelling Unit
|
||||||
Ref: NEC(India) :2011
|
||||||
No.
|
Description
|
Area for
the Main Dwelling Unit (m2)
|
||||
35 mm2
|
45 mm2
|
55 mm2
|
85 mm2
|
140 mm2
|
||
1
|
Light
points
|
7 No
|
8 No
|
10 No
|
12 No
|
17 No
|
2
|
Ceiling
fans Pont
|
2 No
|
3 No
|
4 No
|
5 No
|
7 No
|
3
|
Ceiling
fans No’s
|
2 No
|
2 No
|
3 No
|
4 No
|
5 No
|
4
|
6A Socket
outlets
|
2 No
|
3 No
|
4No
|
5 No
|
7 No
|
5
|
16A Socket
outlets
|
–
|
1 No
|
2 No
|
3 No
|
4No
|
6
|
Call-bell
(buzzer)
|
–
|
–
|
1 No
|
1 No
|
1 No
|
Recommended Schedule of Socket-Outlets
|
||
Ref: NEC(India) :2011
|
||
Description
|
Number of
Socket
|
|
6A Socket
|
16A Socket
|
|
Bedroom
|
2
|
1
|
Living
room
|
2
|
2
|
Kitchen
|
1
|
2
|
Dining
room
|
2
|
1
|
Garage
|
1
|
1
|
For
refrigerator
|
–
|
1
|
For
air-conditioner
|
–
|
1 for each
|
Verandah
|
1 per
10mter2
|
1
|
Bathroom
|
1
|
1
|
Power requirements of the building
|
||
Ref: NEC(India) :2011
|
||
Part of ElectricalInstallation
|
Part of
the Total Power Requirement in %
|
DiversityFactor
|
Ventilation,
heating (air-conditioning)
|
45%
|
1.0
|
Power
plant (drives)
|
52%
|
0.65
|
Lighting
|
30%
|
0.95
|
Lifts
|
20%
|
1.0
|
Kitchen
|
10%
|
0.6
|
Laundry
|
5%
|
0.6
|
Lift Car Speed
|
||
Ref: NEC(India) :2011
|
||
Occupancy
|
No. of
Floors Served
|
Car
Speed m/s
|
Office
building
|
4 to 5
|
0.5 to
0.75 m/sec
|
Office
building
|
6 to 12
|
0.75 to
1.5 m/sec
|
Shops and
departmental stores
|
13 to 20
|
More than
1.5 m/sec
|
Passenger
lifts for low and medium lodging houses
|
–
|
0.5 m/sec
|
Hotels
|
4 to 5
|
0.5 to
0.75 m/sec
|
Normal
load carrying lifts
|
–
|
2.0 to 2.5
m/sec
|
Hospital
passenger Lift
|
4 to 5
|
0.5 to
0.75 m/sec
|
Hospital
passenger Lift
|
13 to 20
|
More than
1.5 m/sec
|
Hospital
bed lifts (Short travel lifts insmall hospitals)
|
–
|
0.25 m/sec
|
Hospital
bed lifts (Normal)
|
–
|
0.5 m/sec
|
Hospital
bed lifts (Long travel lifts inGeneral hospitals)
|
|
0.6 to 1.5
m/sec
|
Capacitor Ratings at Rated Voltage
|
||||||
Ref: NEC(India) :2011
|
||||||
Motor Rating(Kw)
|
Capacitor
Rating in kVAR for Motor Speed
|
|||||
3
000rev/min
|
1
500rev/min
|
1
000rev/min
|
750rev/min
|
600rev/min
|
500rev/min
|
|
2.25
|
1
|
1
|
1.5
|
2
|
2.5
|
2.5
|
3.7
|
2
|
2
|
2.5
|
3.5
|
4
|
4
|
5.7
|
2
|
3
|
3.5
|
4.5
|
5
|
5.5
|
7.5
|
3
|
4
|
4.5
|
5.5
|
6
|
6.5
|
11.2
|
4
|
5
|
6
|
7.5
|
8.5
|
9
|
15
|
5
|
6
|
7
|
9
|
11
|
12
|
18.7
|
6
|
7
|
9
|
10.5
|
13
|
14.5
|
22.5
|
7
|
8
|
10
|
12
|
15
|
17
|
37
|
11
|
12.5
|
16
|
18
|
23
|
25
|
57
|
16
|
17
|
21
|
23
|
29
|
32
|
75
|
21
|
23
|
26
|
28
|
35
|
40
|
102
|
31
|
33
|
36
|
38
|
45
|
55
|
150
|
40
|
42
|
45
|
47
|
60
|
67
|
187
|
46
|
50
|
53
|
55
|
68
|
76
|
:Maximum Current Demand for Motor:
|
||
Ref: NEC(India) :2011
|
||
Nature of supply
|
Size of
installation
|
Maximum
current demand
|
Single
phaseor Three phase
|
Up to and including
0.75 kW
|
Six times
the full load current
|
Above 0.75
kW and up to 7.5 kW
|
Three
times the full load current
|
|
Above 7.5
kW up to and up to11 kW
|
Two times
the full load current
|
|
Above 11
kW
|
One and
half times the full load current
|
Rated Basic Insulation Level (BIL)
|
|
Ref: NEC(India) :2011
|
|
Nominal System Voltage (kV)
|
Rated BIL
(kVp)
|
33 KV
|
170
|
22 KV
|
125
|
11 KV
|
75
|
6.6 KV
|
60
|
3.3 KV
|
40
|
Illumination Level
|
|
Ref: NEC(India) :2011
|
|
Location
|
Illumination
Level (Lux)
|
Residence
|
|
Entrance /
Hallways
|
100
|
Living
room
|
300
|
Dining
Room
|
150
|
Bed Room
(General)
|
300
|
Bed Room
(Dressing , Bed Heads)
|
200
|
Kitchen
|
200
|
Kitchen
sink
|
300
|
Bathroom
|
100
|
Sewing
|
700
|
Workshop
|
200
|
Staircase
|
100
|
Garage
|
70
|
Study Room
|
300
|
Office
Building
|
|
Entrance
hall / Reception
|
150
|
Conference
Room / Executive Office
|
300
|
General
Office Space
|
300
|
Business
Machinery Operation
|
450
|
Drawing
Office
|
450
|
Corridors
|
70
|
Stairs
|
100
|
Lift
landing
|
150
|
Hospital
Building
|
|
Reception
& Waiting
|
150
|
General
ward
|
100
|
Bed Side
|
150
|
Toilet
|
70
|
Stairs
|
100
|
Operation
Theatre (General)
|
300
|
Operation
Theatre (Operation Table)
|
Special
|
Laboratories
|
300
|
Radiology
|
100
|
Causality
|
150
|
Dispensaries
|
300
|
Laundry
|
200
|
Dry
Cleaning
|
200
|
Ironing
|
300
|
General
Office
|
450
|
Kitchen
|
200
|
Assembly
& Concert Halls
|
|
Foyers
|
100 to 150
|
Auditoria
|
100 to 150
|
Platform
|
450
|
Corridors
|
70
|
Stairs
|
100
|
Cinema
Halls
|
|
Foyers
|
150
|
Auditoria
|
50
|
Corridors
|
70
|
Stairs
|
100
|
Theatres
|
|
Foyers
|
150
|
Auditoria
|
70
|
Corridors
|
70
|
Stairs
|
100
|
School /
College Building
|
|
Assembly Halls
|
|
General
|
150
|
Examination
center
|
300
|
Platform
|
300
|
Classes
|
|
Desktop
|
300
|
Blackboard
|
200 to 300
|
Libraries
|
|
Shelves
|
70 to 150
|
Reading
Room
|
150 to 300
|
Reading
Table
|
300 to 700
|
Cataloguing
|
150 to 300
|
General
|
|
Office
|
300
|
Staff Room
|
150
|
Corridors
|
70
|
Stairs
|
100
|
Lamp’s Lumen Data
|
||
Rating (Watt)
|
Life
(Hours)
|
Initial
Lumens
|
Incandescent
Lamp
|
||
60
|
1000
|
870
|
100
|
750
|
1750
|
150
|
2000
|
1740
|
200
|
2000
|
2300
|
500
|
2000
|
6500
|
Fluorescent
Lamp
|
||
18
|
7000
|
1120
|
20
|
7000
|
1020
|
36
|
7000
|
2800
|
40
|
7000
|
2700
|
2X40
|
7000
|
4000
|
Compact
Fluorescent Lamp
|
||
5
|
10000
|
220
|
7
|
7000
|
380
|
11
|
7000
|
560
|
13
|
7000
|
680
|
15
|
7000
|
810
|
18
|
7000
|
1050
|
23
|
7000
|
1500
|
26
|
7000
|
1800
|
32
|
7000
|
2400
|
Mercury
Vapour Lamp
|
||
100
|
18000
|
3700
|
175
|
24000
|
8600
|
250
|
24000
|
12100
|
400
|
24000
|
22500
|
1000
|
24000
|
57000
|
Metal
Halide Lamp
|
||
50
|
15000
|
3400
|
70
|
15000
|
5600
|
100
|
15000
|
9000
|
150
|
10000
|
13500
|
175
|
10000
|
15000
|
250
|
10000
|
20500
|
400
|
20000
|
36000
|
1000
|
12000
|
110000
|
High
Pressure Sodium Vapour Lamps
|
||
35
|
16000
|
2250
|
50
|
24000
|
4000
|
70
|
24000
|
5800
|
100
|
24000
|
9500
|
150
|
24000
|
16000
|
250
|
24000
|
27500
|
400
|
24000
|
47500
|
1000
|
24000
|
140000
|
Pulse
Start Metal Halide Lamp
|
||
50
|
15000
|
3400
|
70
|
15000
|
5600
|
100
|
15000
|
9000
|
150
|
15000
|
15000
|
175
|
15000
|
17500
|
200
|
15000
|
21000
|
250
|
15000
|
26300
|
320
|
20000
|
34000
|
400
|
20000
|
44000
|
450
|
20000
|
50000
|
:Duty Type of Motor:
|
||
Ref: IS-325
|
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Duty Type Symbol
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Duty Type
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Application
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S1
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Continuous
Duty
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Pumps,
Bowers, Compressors, Fans
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S2
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Short Time
Duty
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Siren,
Flood relief Gates
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S3
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Intermittent
Periodic Duty
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Valve,
Actuators, Wire drawing machine
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S4
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Intermittent
Periodic Duty with starting
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Hoist,
Cranes, Lifts, Escalators
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S5
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Intermittent
Periodic Duty with starting / Breaking
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Hoist,
Cranes (with electronics Breaks), Rolling mills
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S6
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Continuous
Duty with Intermittent Periodic Duty
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Machine
tools, Conveyors
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S7
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Continuous
Duty with starting / Breaking
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Machine
tools,
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S8
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Continuous
Duty with periodic load changes
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Pole
Channing Applications
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Type of Distribution System
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As per IEC 60364-3
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Unearthed System
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Earthed
System
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IT
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TT / TN (TN-S,TN-C,TN-C-S)
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First
Letter (the neutral point in relation to earth):T= directly earthed neutral
(from the French word Terre)I =unearthed or high impedance-earthed neutral
(e.g. 2,000 Ω)
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Second
letter (Exposed conductive parts of the electrical installation in relation
to earth):T =directly earthed exposed conductive partsN =exposed conductive
parts directly connected to the neutral conductor
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Totally copy past from www.electricalnotes.wordpress.com
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