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2 X 600 MW SINGHITARAI THERMAL POWER PROJECT SINGHITARAI - CHHATTISGARH
Owner:
ATHENA CHHATTISGARH POWER PVT. LTD., In Front of Carmel School, Near Guru Building, Govind Garden, Laxmipur, Raigarh, Chhattisgarh - 496001
Owners Engineer:
ENERGY INFRATECH PVT.LTD. Thermal Power Divison, 7-1-24, B Block, 5th Floor, Roxana Towers, Greenlands, Begumpet, Hyderabad-500016 Ph No.:91-40-66570881, Fax No.:91-40-66570888
EPC Contractor:
ABIR Infrastructure Private Limited, Thermal Power Divison, 7-1-24, B Block, 5th Floor, Roxana Towers, Greenlands, Begumpet, Hyderabad-500016 Ph No.:91-40-66570881, Fax No.:91-40-66570888
Consultant To EPC Contractor:
TPSC(I) PRIVATE LIMITED (Wholly owned subsidiary of Toshiba Plant Systems & Services Corporation, Tokyo, Japan)
A-1 Module, D - Quadrant, 2nd Floor, Cyber Towers, Hi-Tec City, Madhapur, Hyderabad - 500 081, INDIA
Document Title: DBR FOR CABLE SELECTION AND SIZING
ABIR Document No.:
STPP-5311-E-11-03-3001, Rev-00
Consultant Doc. No.
E-TSC1-725-14-3001, Rev. 0
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 1 of 17
DOCUMENT CONTROL SHEET
0 20-04-11 First Issue AM RB DN MS
REV
NO DATE STATUS
INTLS SGN INTLS SGN INTLS SGN INTLS SGN
PREPARED BY CHECKED BY APPROVED BY ISSUE
AUTHORISATION
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 2 of 17
CONTENTS
Sl. No Particulars Page No.
1.00.00 PURPOSE 2
2.00.00 PLANT INFORMATION 3
3.00.00 REFERENCE DOCUMENTS:- CODES & STANDARDS 4
4.00.00 CABLE SELECTION & SIZING CRITERIA 5
5.00.00 ELECTRICAL NETWORK CHARACTERSTICS 5
6.00.00 TECHNICAL REQUIREMENT OF CABLE 6
7.00.00 SIZING OF POWER CABLE 9
8.00.00 SIZING OF CONTROL CABLE 16
9.00.00 CONCLUSION 16
ANNEXURE POLYCAB CATALOGUE FOR DERATING FACTOR 1 SHEET
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 3 of 17
1.00.00 PURPOSE
1.01.00 The aim of this document is to give the method and parameters enabling the calculation for selection and sizing of power cables taking into account the rated current, length between main distribution switchboard and electrical consumers, and the de-rating factors due to site and installation conditions and philosophy for selection of control cables for 2X600 MW Coal based Thermal Power Plant at Singhitarai in Chhattisgarh State of India.
2.00.00 PLANT INFORMATION
1 Owner : ATHENA CHHATTISGARH POWER
PVT LTD.
2 Project Name : 2X600 MW SINGHITARAI THERMAL
POWER PROJECT.
3 Location : Singhitarai, Chhattisgarh
4 Ambient Temperature :
(i) Minimum : 8 degree C
(ii) Maximum : 46.5 degree C
6 Relative Humidity : 35% Min , 88 % Max
6 Seismic Zone : Zone – III, as per 1893-2002
7 Auxiliary Power Supply :
(i) Motors rated 1500 KW &
above.
: 11000 V (±10%), 3 phase, 3W, 50 Hz,
non-effectively earthed.
(ii) AC motors at 200 KW &
below 1500 KW.
: 3300 V (±10%), 3 phase, 3W, 50 Hz,
non-effectively earthed.
(iii) AC motors upto 200 kW. : 415 V, (±10%), 3 phase, 3 wire, 50 Hz,
effectively earthed
(iv) DC alarm control & Protective
devices.
: 220 V DC, 2W, unearthed
(v) DC motors. : 220 V (±10%), 2 wire, unearthed DC
(vi) Lighting fixture and Space
Heaters.
: 240 V, 1 phase, 50 Hz, AC effectively
earthed
(vii) DCS Power supply : 240 V AC, 1 phase, 50 Hz, UPS
(viii) Solid state controls &
annunciation/ local control
panel
: 240 V AC, 1 phase, 50 Hz, non UPS
(ix) Construction Power : 415 V (±10%), 3 phase, 4 wire, 50 Hz
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 4 of 17
±5%, AC with effectively earthed
8 Suitability for Power Supplies
:
(i) AC Supply : Voltage variation ±10%,
Frequency variation ±5%;
Combined Voltage and Frequency
variation 10%
(ii) DC Supply : 198 V to 242 V
9 Design Ambient for Electrical Equipment
: 50.0 degree C
3.00.00 REFERENCE DOCUMENTS-: CODES & STANDARDS
IS-1554-1 : PVC insulated electric cables for working voltages up to and
including 1100V.
IS-7098-1 : Cross linked polyethylene insulated PVC sheathed cables
for working voltages up to and including 1100V.
IS:7098-II : Cross linked polyethylene insulated PVC sheathed cable for
working voltage from 3.3kV upto & including 33 kV.
IS:9968-I : Specification of Elastomer Insulated cables for rated
voltages upto and including 1100V
IS:6380 : Specification of elastomeric insulation and sheath of electric
cables
IS : 3961 : Recommended current ratings for cables
IS : 3975 : Low Carbon Galvanized steel wires, formed wires and tapes
for armouring of cables.
IS : 5831 : PVC insulation and sheath of electrical cables.
IS : 8130 : Conductors for insulated electrical cables and flexible cords.
IEC:287 : Calculations of the continuous current rating of cables(100%
load factor)
IEC:228 : Conductors for insulated cables
IEC:502
: Extruded solid dielectric insulated power cables for rated
voltages from 1.00 kV upto 30 kV
IEC-754-I : Test on gases evolved during combustion of electric cables.
IEEE-383 : Standard for type test of Class IE Electric Cables.
IEC -332 Tests on Electric cables under fire conditions.
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 5 of 17
Part-3 : Tests on bunched wires or cables (category -B)
IEC: 230 Impulse tests on cables and their accessories
IEC-331 Fire resisting characteristics of electric cables
IEC-364-5-
52
Current-carrying capacities in wiring systems-Section 523
Second Edition 2001-08
4.00.00 CABLE SELECTION AND SIZING CRITERIA
4.01.00 Cable sizing criteria for Power cable
The calculation and technical choice of power cables consist of the determination of the normalized conductor in applying simultaneously the three following conditions:
a) Continuous current capacity: The overheating, in permanent overload (thermal
protection current setting), taking into account the site and installation conditions, so
that cable components are not exposed to excessive temperature value.
b) Short time rating: The possibility to carry without degradation, an accidental over
current at the end of the cable, taking into account protection devices.
c) Voltage drop criteria: The voltage drop caused by the current flowing in cores
restricted to a value allowing the starting and the permanent loading of the consumers.
The conditions (a) and (b) give the minimal cross section of the conductor. Condition (b) will be applied for all HT feeders and for feeders controlled by ACB’s in case of LV system. Cables shall be sized for rated short circuit current of the respective Swgrs/Boards/MCCs. Feeders controlled by fuses/MCB’s/MCCB’s will not be sized for short circuit rating.
The condition (c) gives the maximum length, which can’t be exceeded, in order to comply with the maximum admissible voltage drop. If the length permitted by conditions (c) is insufficient, it will be necessary to increase the cable cross-section consequently.
5.00.00 ELECTRICAL NETWORK CHARACTERISTICS
5.01.01 Electrical Network Characteristics
A For HT system
Rated voltage (General network) : 11 kV AC 3 phase & 3.3 kV AC 3 phase.
Frequency : 50 Hz
Maximum Voltage drop in the
cable from transformer to
Panel.
: 2% (rated conditions)
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 6 of 17
Maximum Voltage drop in the
cable from Panel to Motor
: 3% (full load running conditions)
Maximum voltage drop in the
cable during starting of motor. :
15%
Short Circuit Current for HT
Switchboard. :
40kA for 1 sec for both voltage grading.
(Shall be decide as per short circuit study)
Calculated Maximum Short
Circuit Current. : As per short circuit study
B For LT system
Rated voltage (General network) : 415 V AC three phase / 240V AC Single phase
/ 220V DC.
Frequency : 50 Hz
Maximum Voltage drop in the
cable from transformer to MCC. : 2% (rated conditions)
Maximum Voltage drop in the
cable from MCC to Motor. : 3% (full load running conditions)
Maximum voltage drop in the
cable during starting of motor. : 15%
Maximum voltage drop from
UPS to load end. 5% (full load running conditions)
Short Circuit Current for LV
Switchboard :
50 /65 kA rms
(Shall be decide as per short circuit study)
Calculated Maximum Short
Circuit Current. : As per short circuit study
6.00.00 TECHNICAL REQUIREMENT OF CABLES
A.For HT System
Core : Single/Multi core, Multi stranded bare
Aluminum
Shape of conductor : Compacted Round
Grade : 11/11(UE) kV for 11 kV System & 3.3/3.3
(UE) kV for 3.3 kV System.
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 7 of 17
Conductor Screen : Triple Extruded semi-conducting
compound.
Insulation : Extruded XLPE
Insulation Screen : Extruded semi-conducting compound in
combination with a layer of lapped copper
tape.
Maximum permissible conductor
temperature:
A ) For continuous operation
B ) Short circuit condition
:
:
90 deg C
250 deg C
Inner sheath : Extruded PVC Compound type ST-2
Armouring (Directly buried cable)
A ) For single core cable
B ) For multi core cable
Aluminium round wire Galvanised steel round wire
External sheath : Extruded FRLS, anti termite & anti rodent
PVC type ST-2. Flame retardant property
shall be as per IEC-60332 Cat C.
Oxygen index : Min. 29 (As per ASTMD 2863)
Acid gas emission : Max. 20% (As per IEC-754-I)
Smoke Density : Light transmission of min. 40% after the
Test.
** For Cable area >= 240 sqmm, shall be considered as single core cable.
B. For LT System (Power Cable)
Core : Single core/ Multi core, Multi-stranded
bare compacted plain aluminium
for sizes greater or equal to 6 sq. mm.
Less than 6 sqmm shall be copper
Conductor.
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 8 of 17
Grade : 1100 V
Insulation XLPE:- For area >= 120 sqmm.
PVC:- For area < 120 sqmm
Maximum permissible conductor
temperature:
A ) For continuous operation
B ) Short circuit condition
90 deg C for XLPE, 70 deg C for PVC
250 deg C for XLPE, 160 deg C for PVC
Inner sheath Extruded PVC compound type- ST2 for
XLPE insulated cable.
Extruded PVC compound type- ST1 for
PVC insulated cable.
Armouring (Directly buried cable)
A ) For single core cable
B ) For multi core cable
Aluminium round wire Galvanised steel round wire
External sheath Extruded FRLS, anti termite & anti rodent
PVC compound type- ST2 for XLPE
insulated cable. Flame retardant property
shall be as per IEC-60332 Cat C.
Extruded FRLS, anti termite & anti rodent
PVC compound type- ST1 for PVC
insulated cable. Flame retardant property
shall be as per IEC-60332 Cat C.
Oxygen index Min. 29 (As per ASTMD 2863)
Acid gas emission : Max. 20% (As per IEC-754-I)
Smoke Density : Light transmission of min. 40% after the
Test.
Cores of the cables shall be identify by coloring of insulation. Following color scheme shall be adopted:
1 core - Black
2 core - Red & Black
3 core - Red, Yellow & Blue
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 9 of 17
4 core - Red, Yellow, Blue and Black
For reduced neutral conductors the core shall be black.
** For Cable area >= 240 sqmm, shall be considered as single core cable.
C. For Control Cables
Core : Multi stranded plain annealed copper.
(Class-2 as per IS 8130)
Shape of conductor : Circular
Conductor cross section : 2.5 sq. mm
Grade : 1100 V
Insulation : Extruded PVC compound type-A
Maximum permissible conductor temperature:
A ) For continuous operation
B ) Short circuit condition
: 70 deg C : 160 deg C
Inner sheath : Extruded PVC compound type ST-1
Armouring ( Directly buried cable) For multi core cable
: Galvanised steel round wire
External sheath
: Extruded FRLS, anti termite & anti rodent PVC compound type –ST1. Flame retardant property shall be as per IEC-60332 Cat C.
Oxygen index
: Min. 29 (As per ASTMD 2863)
Acid gas emission : Max. 20% (As per IEC-754-I)
Smoke Density : Light transmission of min. 40% after the
Test.
Cores of the cables of upto 5 cores shall be identified by colouring of insulation. Following colour scheme shall be adopted.
2 core - Red & Black
3 core - Red, Yellow & Blue
4 core - Red, Yellow, Blue and Black
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 10 of 17
5 core - Red, Yellow, Blue, Black and Grey
For cables having more than 5 cores, core identification shall be done by numbering the insulation of cores sequentially, starting by number 1 in the inner layer (e.g. say for 10 core cable, core numbering shall be from 1 to 10). All the numbers shall be of same color. The color of insulation for all cores shall be grey only.
7.00.00 SIZING OF POWER CABLE
A. Cable sizes based on short circuit current consideration
Short circuit current and the time duration are related with the following formula :
I12t1 = I2
2t
Where,
2
I1 = Short circuit current for t1
I
second
2 = Short circuit current for t2
The short circuit current & interrupting time shall be as under:
second
1. For 11kV – 40kA – 0.2 sec for outgoing motor feeders.
40kA – 0.2 sec for outgoing transformer feeders
40kA – 1 sec for tie feeders
2. For 3.3kV – 40kA – 0.2 sec for outgoing motor feeders
3. For 415V--- 50/65kA – 0.2 sec for outgoing motor feeders
50/65kA – 0.2 sec for outgoing transformer feeders
50/65kA – 1 sec for tie feeders
For Fuse/MCB/MCCB protected feeders, minimum cross section criteria will not apply. In
that feeders continuous current rating and voltage drop will be the deciding factor for
selecting the suitable cables.
Also Outgoing feeders where only IDMTL protection is provided, 1 sec shall be considered
for cable sizing.
With the above formula the equivalent fault current for 1 second is calculated and the
corresponding cable cross sectional size is selected from cable catalogue.
B. Cable sizes based on maximum continuous load current
(1) The allowable continuous current rating of cable shall be calculated using the
following formula:
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 11 of 17
Io ≥ Ie / K
R
Where
Io - Allowable continuous current rating of cable in Amps
Ie - Rated current of equipment in Amps
KR
Cables
- Overall Derating factor due to temperature and grouping of
(2) Derating factors
a) Ambient temperature derating factor : K
T
3 - 21 - 2 = KT ΘΘ
ΘΘ
Θ2 = Core maximum temperature (90° C for XLPE insulation)
(70° C for PVC insulation)
For cables in trays, trenches, racks
Θ 1 = Design temperature for aerial cables: 50° C
Θ 3 = Reference ambient air temperature: 40° C (as per vendor catalogue)
40 - 9050- 90 = KT = 0.89 (For XLPE cable)
40 - 0750- 07 = KT = 0.81 (For PVC cable)
For cables laid directly in ground
Θ 1 = Design temperature for aerial cables: 40° C
Θ 3 = Reference ambient ground temperature: 30° C (as per vendor catalogue)
30 - 9040- 90 = KT = 0.91 (For XLPE cable)
30 - 0740- 07 = KT = 0.86 (For PVC cable)
b) Cable Group derating factor: KL
This factor depends on the type of laying (touching / spaced), type of cable (single / multi
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 12 of 17
core), number of trays and number of cables.
The cable group derating factor is considered in line with manufacturer`s catalogue & the
same is attached as ANNEXURE-I. As per manufacturer`s recommendations, the group
derating factor for cables in cable trays are listed below.
Sl. No.
Type of Cable Type of laying Group Derating Factor
(KL)
1 Single Core
Cables
Trefoil formation with 2
Dia Spacing 0.79
2 Multi Core
Cables Touching Formation 0.66
3
Single core
cable directly
laid in ground
Touching formation 0.73
4
Multi core
cable directly
laid in ground
Touching Formation 0.75
c) Overall Derating Factor: KR
Overall Derating factor (K
For cables in trays, trenches, racks
R ) = Temperature Derating factor (KT
Group Derating Factor (K
) X
L
Sl.No.
)
Type of Cable
Type of laying Overall Derating Factor (KR) for
XLPE cable
Overall Derating Factor (KR) for
PVC cable
1 Single Core
Cables
Trefoil formation
with 2 Dia
Spacing
0.70
Not required
2 Multi Core
Cables
Touching
Formation 0.59
0.53
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 13 of 17
Overall Derating factor (K
For cables laid directly in ground
R ) = Temperature Derating factor (KT
Group Derating Factor (K
) X
L
Thermal resistivity of soil.
) X Derating for depth of laying X
For 11kV / 3.3kV cables, depth of laying is considered as 0.9M as per IS 1255 and Thermal
resistivity of soil is 2000
Sl.No.
Ccm/W (assumed). Based on Manufacture’s catalogue attached in
Annexure-1, derating factor for depth of laying and thermal resistivity of soil are considered
1 & 0.89 respectively.
Type of Cable
Type of laying Overall Derating Factor (KR) for
XLPE cable
Overall Derating Factor (KR) for
PVC cable
1 Single Core
Cables
Spacing of 45cm
between trefoils,
directly laid in
ground
0.59 Not required
2 Multi Core
Cables
Spacing of 45cm
between trefoils,
directly laid in
ground
0.60 0.57
(3) Rated Current Computation:
The rated current (Ie) of the equipment shall be calculated using the following equation.
(a) At normal operation. P x 1000 Ie =
Ki x V x η x Cosθ Where:
Ie = Rated current of equipment in Amps.
P = Rated output of equipment in kW
V = Rated voltage in Volts.
η = Efficiency.
Cosθ = Power factor.
Ki = Coefficient
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 14 of 17
(b) At starting of the motor
Is = Ks x Ie Where:
Is = Starting current of motor
Ks = Starting current ratio
The rated values of equipment (Ie, Is, Cosθ etc.) shall be obtained from the single line
diagrams, motor data sheet etc. or the same may be taken as per Table-1.
TABLE-1
RATED CURRENT OF EQUIPMENT
ITEM 415V / 240V MOTOR
MOTORISED VALVES & DAMPERS
TRANSFORMER & OTHER FEEDERS
DC MOTOR
& FEEDER
S SYSTEM AC DC CIRCUIT 3φ 3W 1φ2W 1φ2
W 3φ3W & 4W 1φ 2W
Ki √ 3 1 1 √ 3 1 RATED
CURREN
T (AT
NORMAL
OPERATI
ON) , Ie
(Amps)
P (kW)
P x 1000
√ 3 x V x η x Cosθ
Px1000
V x η x Cosθ P x1000
√3xVxηx Cosθ
Px1000
V P
(KVA) P x 1000
√ 3 x V x η Px1000
V x η
Px1000
V Px1000
√ 3 x V x η
Power Factor & Efficiency
P(kW) η Cosθ P(kW)
η Cosθ ηxCosθ ηxCosθ ηxCosθ
<2.2 0.65 0.8 <2.2 0.65 0.65 1
0.8
1 >2.2 to
<15 0.85 0.8 >2.2 0.85 0.65
>15 to <90
0.93 0.8
>90 0.94 0.85 Ks 6.0 6.0
1.0 2
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 15 of 17
For 11Kv / 3.3kV MV Motors, efficiency of 0.95 and power factor of 0.9 can be considered and the starting current can be taken as 6 times of full load current for motor rated upto and including 1500kW, 5 times of full load current for motor rated above 1500kW and 4.5 times of full load current for motor rated above 5000kW.
NOTE : THE ABOVE DATA IS BASED ON INFORMATION FROM VARIOUS MANUFACTURERS
AND OUR STANDARDS USED FOR VARIOUS PROJECTS.
C. Cable sizes based on voltage drop calculation criteria
The allowable voltage drop of cable over the rated voltage of equipment shall be limited to
2% between Transformer to MCC and 3% between MCC to Motor at full load running
condition and 15% during motor starting condition. Lighting cables shall be sized to limit the
voltage drop from main lighting distribution board (MLDB) to lighting panel (LP) as 3%.
The voltage drop is calculated using the maximum size calculated in 7.00.00(A) and
7.00.00(B) above by the following formula.
(a) At normal/running operation
Vn = Kv x Ie x L x (R Cosθ + Xc Sinθ)
(b) At starting of motor
Vs = Kv x Is x L x (R Cosϕ + Xc Sinϕ) Where:
Vn, Vs = Voltage drop of cable
Kv = Coefficient
Ie = Rated current of equipment
Is = Starting current of equipment
L = Length of cable in KM
R = Resistance of cable (Ω / Km) at max continuous
temperature of conductor Rac- for AC circuit & Rdc- for
DC circuit
Xc = Cable reactance (Ω/ Km)
Cosθ = Normal/running Power factor
Cosϕ = Starting Power factor
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 16 of 17
TABLE-2
VOLTAGE DROP IN THE CABLE
ITEM 415V MOTOR MOTORISED VALVES
&
DAMPERS
TRANSFORMER &
OTHER FEEDERS
DC MOTOR &
FEEDERS
SYSTEM AC DC
CIRCUIT
3φ 3W
1φ 2W
1φ 2W
3φ 3W &
4W
1φ 2W
Kv √ 3 2 2 √ 3 2
VOLTAGE
DROP OF
CABLE
(V)
Vn
AT NORMAL OPERATION
√3 x Ie x L x (Rac Cosθ+ Xc
Sin θ )
AT NORMAL OPERATION
2 x Ie x L x (Rac Cosθ+
Xc Sin θ )
2 x
Ie x Lx
(Rac Cosθ
+
Xc Sin θ )
√3 x
Ie x Lx
(Rac Cosθ +
Xc Sin θ )
2x Ie x L x Rdc
Vs
AT STARTING OF THE
MOTOR
√3 x Is x L x (Rac Cosϕ+ Xc
Sin ϕ )
AT STARTING OF THE
MOTOR
2 x Is x L x (Rac Cosϕ+
Xc Sin ϕ )
For Motor feeders
2x Is x L x Rdc
POWER FACTOR
Cosθ
&
Sin θ
P
KW
Sinθ Cosθ P
KW
Sin θ Cosθ
Sin θ = 0.52
Cosθ = 0.85
----
AT NORMAL OPERATION
<90
0.6
0.8
<2.2
0.76
0.65
>90
0.53
0.85
>2.2
0.76
0.65
AT STARTING OF MOTOR
----
----
<90
0.93
0.35
<2.2
0.76
0.65
>90
0.95
0.30
>2.2
0.76
0.65
For 11Kv / 3.3kV MV Motors, running power factor of 0.9 and starting power factor of 0.3 will be considered. NOTE : THE ABOVE DATA IS BASED ON INFORMATION FROM VARIOUS MANUFACTURERS AND
OUR STANDARDS USED FOR VARIOUS PROJECTS.
DBR FOR CABLE SELECTION & SIZING
Project
2 X 600 MW SINGHITARAI THERMAL POWER PROJECT
AT SINGHITARAI, CHHATTISGARH Doc. No.: E-TSC1-725-14-3001
Rev 0
Date 18-04-2011 Page 17 of 17
8.00.00 SIZING OF CONTROL CABLE
Minimum size proposed for control cables will be 1.5 sq. mm. For current transformer secondary circuits 4.0 sq. mm minimum cross section shall be used for each phase and for potential transformer secondary circuits, the minimum cross section of the conductors shall be 4 sq. mm. The minimum number of spare cores in control cables shall be as follows:
No. of cores in cable
2C, 4C NIL
Min. No. of spare cores
5C-6C 1
7C-13C 2
14C & above 3
9.00.00 CONCLUSION
According to 7.00.00(A) & 7.00.00(B) calculations the cable cross section is sufficient to
carry the current during normal as well as short circuit conditions.
As per 7.00.00(C) calculation the cable voltage drop with the cross sections calculated will
always be limited to 2-3% during normal operation and 15% during the motor starting
condition.
The above criterion defines the basis for selection and sizing of the cables. For package
vendors, this will be used as a broad guideline. The final selection of the cables shall be the
maximum of the sizes calculated according to 7.00.00(A),(B) &(C) and shall be standardized so
as to optimize the number of cables sizes proposed for this project. The cable sizing calculation
shall be submitted as a separate document.
ANNEXURE-I
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ANNEXURE-I
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