21
ELECTRICAL CABLE SIZING

Electrical Cable Sizing(2)

Embed Size (px)

Citation preview

Page 1: Electrical Cable Sizing(2)

ELECTRICAL CABLE SIZING

Swastioko Budhi
Migas Indonesia
Page 2: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 2 of 21

Page 2 of 21

Table of Contents

1.0 G E NE R AL C ONS IDE R AT IONS 3

1.1 S hort C ircuit C urrent R ating 3

1.2 Voltage Drop 3

1.3 C able C urrent R ating 3

1.4 Other F requency 6

1.5 R es is tance Data 6

2.0 ME THODOL OG Y 6

2.1 F ull L oad C urrent (IF L) C alculations 6

2.2 C able Volt Drop C alculations 7

2.3 HV C able s izing (S hort C ircuit R ating) 8

3.0 S AMP L E – OXY P R OJ E C T 9

3.1 G eneral Data 9

3.2 C as e S tudy I - HV C able S izing 9

3.3 C as e S tudy II - L V C able S izing 13

4.0 C AB L E E L E C TR IC AL DAT A 18

4.1 C able R es is tance (Nexans Technical Data for OXY P roject) 18

4.2 C able R eactance (Nexans Technical Data for OXY P roject) 19

4.3 C able C urrent R ating (Nexans Technical Data for OXY P roject) 20

4.4 C able S hort C ircuit R ating (Nexans Technical Data for OXY P roject) 20

5.0 C ONC L US ION 21

6.0 AP P E NDIE S 21

Page 3: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 3 of 21

Page 3 of 21

1.0 GENERAL CONSIDERATIONS

o Thermal short circuit capacity (for H.V Cables)

o Voltage drop

o Current rating

o Maximum cable loop impedance for earth faults shall not exceeding 1s under solider earth fault conditions. It is meanly for long distance cables.

1.1 Short Circuit Current Rating

The short circuit breaking current of the source switchboard also takeing into account the short circuit limiting characteristics of, e.g., fuse, relays, CBs.

The fault clearance time associated with operation of the primary, see section 2.2.

1.2 Voltage Drop

Voltage drop under steady state and motor starting condition with standard (DEP 33.64.10.10-Gen.) and project requirements. In normally shall be follows

o Less than 5% based on continuous maximum current loading and rated voltage in A.C cables.

o Less than 20% of the rated equipment voltage during motor starting

o Less than 5% from min. system voltage at distribution board and the min. equipment operation voltage in DC cables.

1.3 Cable Current Rating

1.3.1 Rating factor for cable ampaciry

o Onshore

• Depth of laying (IEE wiring regulations 16th 19991)

Correction factor shall be considered if cables in enclosed trench 450mm wide by 300mm deep minimum. Correction factor shall be applied based on Table 4B3- Method 18 (Refer to appendix – C)

Correction factor shall be considered if cables in enclosed trench 450mm wide by 600mm deep minimum. Correction factor shall be applied based on Table 4B3-Method 19 (Refer to appendix – C).

Correction factor shall be considered if cables in enclosed trench 450mm wide by 760mm deep minimum. Correction factor shall be applied based on Table 4B3-Method 20 (Refer to appendix – C).

Page 4: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 4 of 21

Page 4 of 21

For example:

A correction factor of 0.80 shall be applied for conductor cross-section area 10mm2 cables if 6 single-core cables, 4 two-core cables or 3 three or four-core cables are laying the ground.

• Soil thermal resistively

• Ground/ambient temperature (see offshore statement)

o Offshore

• Ground/ambient temperature (IEE wiring regulations 16th 19991)

This derating (correction) factor is determined by design temperature.

♦ Correction factor for ambient temperature where protection is against short-circuit. Refer to Table 4C1 (Refer to appendix - D)

♦ Correction factor for ambient temperature where the overload protective device is a semi-enclosed fuse to BS3036. Refer to Table 4C2 (Refer to appendix - D)

Table 4C1 & 4C2 show correction factor is 1 if cable in air based on ambient temperature on 300C, For example a correction factor of 0.91 shall be applied for XLPE & EPR cables and 0.87 for PVC if maximum design ambient temperature is 400C required by project. The choice of the type of insulation of the cables shall also consider the ambient temperature correction factor.

• Grouping of cables

There are many methods of installation of cables: such as Open and clipped direct (Method 1), Cables embedded direct in building materials (Method 1), in conduit (Method 3 & 4), in trucking (Method 3), on trays (Method 11), in free air, on cleats, brackets or a ladder (Method 12 & 13), Correction factor for grouped cables shall be applied refer to Tables 4B1, 4B2 and 4B3. (Refer to IEE wiring regulations 16th 19991)

Generally, cable installation offshore shall be laying in cable ladder/tray.

Case 1: in free air – Refer to Table 52-E4 (IEC 60364-5-523) see appendix E

As per IEC60092-352, the current rating values may be considered applicable, without correction factor, for cables bunched together on cable trays, unless more than 6 cables (Diagram 1), which may be expected to operate simultaneously at their full rated current, are laid close together in a cable bunch in such a way that there is an absence of free air circulation around them.

Page 5: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 5 of 21

Page 5 of 21

In this case, a correction factor of 0.79 should be applied on current rating value.

Diagram 1 – Cables bunched (6 cables bunch) and clipped direct to a non-metallic surface

♦ Single core cables – Refer to Table 52-E5 (see Appendix F)

Both HV and LV single core cables shall be arranged in the trefoil formation and shall have a distance of half cable diameter, ½De, from the side of the cable ladder or tray. Multiple runs of trefoils shall also have a space of separation of two cable diameter, 2De, as shown in the Diagram 2 below:

½De De 2De

Diagram 2 – Single core cables installation

All single core cables shall be bunched in trefoil formation, as shown in Diagram 2 above. Since there are less than six cables bunched together, the cable grouping correction factor is 1 applicable in one layer ladder here. However, correction factor 0.97/0.96 shall be applied in two (2)/three (3) layers of ladder respectively.

♦ Multicore cables- Refer to Table 52-E4 (see Appendix E)

HV multicore cables shall be installed in a single layer and touching as shown in Diagram 3 below:

Diagram 3 – HV multicore cables installation

The cable grouping correction factor is 1 applicable in one (1) layer of ladder for one cable only. Others grouping factor refer to table 52-E4 (see Appendix E).

Page 6: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 6 of 21

Page 6 of 21

LV multicore cables may not be installed in single layers and may grouped as bunches of 6 cables, as shown in Diagram 1. A grouping factor 0.73 shall be applied in three (3) layers and six (6) circuits requirement.

• As a result

Derating Factor = ambient temperature correction factor × cable grouping correction factor =0.91 x 0.73 =0.66.

1.4 Other Frequency

In our scope of work, cable for Electrical power system usually shall be 50Hz or 60Hz. High frequency will not be applicable and shall not be covered in this presentation.

1.5 Resistance Data

Normally resistance of cable is provided at 200C by Vendor. The formula for actual resistance as a function of temperature is below.

R=R0 (1+ α (t-200C)

R0: Resistance at t=200C

t Conductor temperature 0C

α 0.00393 for copper

The resistances are based on the maximum cable operating temperature of 85oC (EPR) and 90oC (XLPE) for the different cable type codes selected.

For example:

Resistance at 200C of the 3C-4mm2 cables is 4.70 based on Draka Catalogue page 52 see Appendix A, so Resistance of the XLPE cable shall be

2.0 METHODOLOGY

2.1 Full Load Current (IFL) Calculations

2.1.1 Refer to vendor data or Handbook

2.1.2 Formula

o 3phase circuit for AC system:

FFSYSFL ECOSV

kWI×××

×=

θ31000

R= 4.70 x (1+0.00393 x (900C-200C)) =4.975ohm/km

Page 7: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 7 of 21

Page 7 of 21

Where:

kW Equipment Load

VSYS System voltage (V)

IFL Full load current (A)

θ Angle in which the current lags the voltage (degree)

Eff Power Efficiency

o Single phase circuit for AC system

FFSYSFL ECOSV

kWI××

×=

θ1000

o DC system:

SYSFL V

kWI 1000×=

2.2 Cable Volt Drop Calculations

2.2.1 3phase circuit for AC system:

Where:

VSYS System voltage (V)

%VDROP Volt drop (%)

l Length (m)

IFL Full load current (A)

R Cable resistance (Ω / km)

X Cable reactance (Ω / km)

θ Angle in which the current lags the voltage (degree)

n Number of cables in parallel per phase

1000100)sincos(3

%××

×+×××=

nVXRIl

VSYS

FLDROP

θθ

Page 8: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 8 of 21

Page 8 of 21

2.2.2 Single phase circuit for AC system:

2.2.3 DC system:

2.3 HV Cable sizing (Short Circuit Rating)

HV power cables will also be sized based on their short circuit withstand capability.

ktIA ×

=

where :

A Cable conductor cross-sectional area (mm2)

I Short circuit current (A)

t Duration of short circuit (s).

For feeders protected by circuit breakers, t = 0.4s.

For feeders protected by fuses, t = 0.25s.

K cable conductor material, insulation and the safe temperature rise of the insulation. See-Appendix

1000100)sincos(2

%××

×+×××=

nVXRIl

VSYS

FLDROP

θθ

10001002%

××××××

=nV

RIlVSYS

FLDROP

Page 9: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 9 of 21

Page 9 of 21

3.0 SAMPLE – OXY PROJECT

3.1 General Data

o Correction factor for HV & LV single cable shall be 0.94 x 1 = 0.94

o Correction factor for HV & LV multicore cables shall be 0.94 x 0.85 =0.80.

o All 6.6kV motors shall have starting current not greater than 550%. The starting current of the low voltage motors shall not exceed 600% of full load current.

o Voltage drop under steady state and motor starting conditions with the following limitations:

• 4% during steady state condition from origin of supply and user terminals

• 20% during motor starting

• 2% on feeders to lighting and small power distribution boards

• 2.5% average on lighting and small power sub-circuits

• 4% for d.c. systems

o The cable data refer to the Nexans cable technical data

3.2 Case Study I - HV Cable Sizing

3.2.1 Short Circuit Conditions

6/10kV electrical cables shall be used for the 6.6kV power distribution system. Cables for power distribution shall be sized based on the total current, steady state volt drop and short circuit capacity. Motor feeders shall be sized based on the total current, steady state and motor starting volt drops.

The short circuit rating of 6.6kV Switchboard is 50kA and for feeders protected by circuit breakers, the cable short circuit duration is 0.4 second. 143 refer to table 43A – Values of K for common materials, for calculation of the effects of fault current – (Refer to appendix – B)

2217146

4.050000 mmA =×

=

Therefore, the minimum cable conductor area shall be > 217mm2

For feeders protected by fuses, the cable short circuit duration is 0.25 second.

2172146

25.050000 mmA =×

=

Therefore, the minimum cable conductor area shall be > 172mm2.

Page 10: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 10 of 21

Page 10 of 21

3.2.2 6.6kV Cable Sizing Calculations

G ~

6/10kV Cable 31-E-HD40003

GT-3101A 16.034MVA

6.6kV Switchboard SB-3102A 3150A, 3P 50kA

M ~

PM-3156kW

6/10kV Cable 31-E-HP40225

Page 11: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 11 of 21

Page 11 of 21

o Cable 31-E-HP40003 from Gas Turbine Generator GT-3101A to 6.6kV Switchboard SB-3102

Gas Turbine Generator data

• Rated power = 16.034MVA

• Rated current @ 6.6kV = 1403A

• Cable sizing current = 1403 x 1.15 = 1613A

• Estimated cable length = 60m

• Resistance at 90oC – Refer to Table xx

Cable sizing

No. of cores 1 core per phase

Conductor cross-section area (mm2) 400 (Max.size allowed)

Rated current at 45°C (A) 677

Derating factor 0.94

Derated ampacity (A) 0.94 x 677 = 636

Quantity of cables per phase (round up) 1613 ÷ 636 = 2.54 ≈ 3

Total cable cross-sectional area (mm2) (VCB protected) 3 × 400 = 1200 > 217

Total number of cables installed 3 cables per phase

Resistance at 90oC (Ω/km) (XLPE) 0.0636

Reactance at 50Hz (Ω/km) 0.093

Power factor, Cos θ 0.80

Sin θ 0.60

Percentage volt drop (%) 0.08<4%

Sample calculation:

%08.0660031000

100))60.0093.0()80.00636.0((6014033% . =××

××+××××=∴ − STATESDROPV

Page 12: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 12 of 21

Page 12 of 21

o Cable 31-E-HP40225 Seawater Injection Pump Motor (PM-3156)

Motor data

• Rated motor power = 3750kW

• Full load current = 382A (Vendor data)

• Limited starting current = 1528A (Vendor data)

• Cable sizing for full current = 382 x 1.15 = 439A

• Estimated cable length = 80m

Cable sizing – steady state & motor starting

No. of cores 1 core per phase

Conductor cross-section area (mm2) 300

Rated current at 45°C (A) 565

Derating factor 0.94

Derated ampacity (A) 0.94 x 565 = 531

Quantity of cables per phase (round up) 439 ÷ 531 = 0.85 ≈ 1

Total cable cross-sectional area (mm2) (VCB protected) 1 x 300 = 300 > 217

Total number of cables installed 1 cable per phase

Resistance at 90oC (Ω/km) (XLPE) 0.0797

Reactance at 50Hz (Ω/km) 0.095

Steady state power factor, Cos θ (Vendor data) 0.89 (Sinθ = 0.46)

Motor starting power factor, Cos θ (Vendor data) 0.14 (Sinθ = 0.99)

Percentage volt drop (%) – steady state 0.09<4%

Percentage volt drop (%) – motor starting 0.33<20%

Calculations:

%09.0660011000

100))49.0095.0()87.00797.0((803823% . =××

××+××××=∴ − STATESDROPV

Page 13: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 13 of 21

Page 13 of 21

%33.0660011000

100))99.0095.0()14.00797.0((8015283% . =××

××+××××=∴ − STARTMDROPV

3.3 Case Study II - LV Cable Sizing

3.3.1 Short Circuit Conditions

The short circuit conditions for LV systems are normally not calculated as there are many cables at the downstream to disperse the fault current in the event of a fault. Therefore, the short circuit rating for cables will not be used here.

3.3.2 415V Cable Sizing Calculations

0.6/1kV Cable 31-E-LP40320

0.6/1kV Cable 31-E-LD40101

0.6/1kV Cable 31-E-LP40137

CP

0.6/1kV Cable 31-E-LP40480

Crane

TR-3105 1.6MVA LNAN

ECP-1118A

EH-1118A M-3154

415V Switchboard SB-3103A

Page 14: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 14 of 21

Page 14 of 21

o Cable 31-E-LP40137 from 6.6/0.44kV 1.6MVA Transformer (TR-3105A) to 415V Switchboard (SB-3103)

Transformer data

• Rated power = 1.6MVA LNAN

• Full load current @ 440V= 2099A

• Cable sizing current = 2099 x 1.15 = 2414A

• Estimated Cable length = 45m

Cable sizing

No. of cores 1 core

Conductor cross-section area (mm2) 630

Rated current at 45°C (A) 899

Derating factor 0.94

Derated ampacity (A) 0.94 x 899 = 845

Quantity of cables per phase (round up) 2414 ÷845 = 2.86 ≈ 3

Total number of cables installed 3 cables per phase = 9

Resistance at 90oC (Ω/km) (XLPE) 0.0580

Reactance at 50Hz (Ω/km) 0.097

Steady state power factor, Cos θ 0.80 (Sinθ = 0.60)

Percentage volt drop (%) – steady state 1.29 < 4%

Calculations:

%29.144031000

100))6.0097.0()8.00580.0((4520993% . =××

××+××××=∴ − STATESDROPV

Page 15: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 15 of 21

Page 15 of 21

o Cable(s) 31-E-LP40320 from 415V Switchboard (SB-3103) to Pedestal Crane Package (M-3154)

Motor data

• Motor rating = 200kW

• Full load current = 342A (Vendor data)

• Cable sizing current = 342 x 1.15 = 393A

• Starting current = 6 x 342A = 2052A

• Estimated cable length = 110m

Cable sizing

No. of cores 1 core

Conductor cross-section area (mm2) 240

Rated current at 45°C (A) 492

Derating factor 0.94

Derated ampacity (A) 0.94 x 492 = 462

Quantity of cables per phase (round up) 393 ÷ 462 = 0.85 ≈ 1

Total number of cables installed 1 cable per phase = 3

Resistance at 90oC (Ω/km) (XLPE) 0.108

Reactance at 50Hz (Ω/km) 0.101

Steady state power factor, Cos θ 0.86 (Sinθ = 0.51)

Motor starting power factor, Cos θ 0.30 (Sinθ = 0.95)

Steady state volt drop (%) 2.57 < 4%

Motor starting volt drop (%) 12.09 < 20%

Calculations:

%57.241511000

100))51.0101.0()86.0108.0((1103873% . =××

××+××××=∴ − STATESDROPV

%09.1241511000

100))95.0101.0()30.0108.0((11020523% . =××

××+××××=∴ − STARTMDROPV

Page 16: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 16 of 21

Page 16 of 21

o Cable 31-E-LP40137 from 415V Switchboard (SB-3103) to Fuel Gas Superheater A Thyristor Control Panel (ECP-1118A)

• The voltage drop will be calculated in two stages – from the MCC to the Fuel Gas Superheater Thyristor Panel (35m) and from the Thyristor Panel to the Fuel Gas Superheater A (125m).

• Rated power for Fuel Gas Superheater A (E-1118A) = 385kW

• Full load current = 535A (Vendor data)

• The heater is protected by a breaker whose amp trip rating is 800A. Therefore the cable is sized to withstand 800A.

Cable sizing

No. of cores 1 core

Conductor cross-section area (mm2) 300

Rated current at 45°C (A) 565

Derating factor 0.94

Derated ampacity (A) 0.94 x 565 = 531

Quantity of cables per phase (round up) 800 ÷ 531 = 1.51 ≈ 2

Total number of cables installed 2 cables per phase = 6

Resistance at 90oC (Ω/km) (XLPE) 0.0904

Reactance at 50Hz (Ω/km) (HOLD) 0.100

Steady state power factor, Cos θ 1.00 (∴sin θ = 0)

Percentage volt drop (%) – steady state 0.35

Calculations:

%35.041521000

100))0100.0()00.10904.0((355353% . =××

××+××××=∴ − STATESDROPV

Page 17: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 17 of 21

Page 17 of 21

Cable 31-E-LP40480 from Fuel Gas Superheater A Thyristor Control Panel (ECP-1118A) to Fuel Gas Superheater A (E-1118A)

Cable sizing

No. of cores 1 core

Conductor cross-section area (mm2) 400

Rated current at 45°C (A) 677

Derating factor 0.94

Derated ampacity (A) 0.94 x 677 = 636

Quantity of cables per phase (round up) 615 ÷ 636 = 0.97 ≈ 1

Total number of cables installed 1 cables per phase = 3

Resistance at 90oC (Ω/km) (XLPE) 0.0763

Reactance at 50Hz (Ω/km) (HOLD) 0.100

Steady state power factor, Cos θ 1.00 (∴sin θ = 0)

Total percentage volt drop (%) – steady state 2.13

Calculations:

%13.241511000

100))0100.0()00.10763.0((1255353% . =××

××+××××=∴ − STATESDROPV

Therefore, the final volt drop from SB-3103 to E-1118A = 0.35 + 2.13 = 2.48% < 4%

Page 18: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 18 of 21

Page 18 of 21

4.0 CABLE ELECTRICAL DATA

4.1 Cable Resistance (Nexans Technical Data for OXY Project)

The resistances are based on the maximum cable operating temperature of 85oC (EPR) and 90oC (XLPE) for the different cable type codes selected.

Table 1 – Cable Resistance @ 85oC (EPR) or 90oC (XLPE)

Conductor area

(mm2)

Cable Resistance (Ω/km)

Cable Type Codes

H1 H3 H4 H5 H8 L1 L2 L4 L5

2.5 - - - - - 9.6 9.64 9.49 -

4 - - - - - 5.99 5.99 5.90 -

6 - - - - - 3.97 3.97 3.91 -

10 2.36 - - - - 2.35 2.35 - -

16 1.49 1.48 1.48 - - 1.48 1.48 1.46 -

25 0.944 0.936 0.936 - 0.922 0.939 0.937 - -

35 0.683 0.675 0.675 - 0.664 0.677 0.676 0.664 -

50 0.508 0.499 0.499 - 0.491 0.502 0.500 - -

70 0.354 0.345 0.345 - 0.339 0.349 0.346 - -

95 0.260 0.249 0.249 - 0.245 0.254 0.251 0.245 0.245

120 0.208 0.197 0.197 - 0.194 0.203 0.200 0.193 -

150 0.173 0.162 0.162 - 0.159 0.168 0.165 - -

185 0.142 0.129 0.129 - 0.127 0.137 0.133 - -

240 0.113 0.0990 0.0996 - 0.0979 0.108 0.103 - -

300 0.0971 0.0797 - 0.0779 - 0.0904 - - -

400 - 0.0636 - - - 0.0763 - - -

500 - 0.0510 - - - 0.0660 - - -

630 0.0635 0.0416 - - - 0.0580 - - -

Page 19: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 19 of 21

Page 19 of 21

4.2 Cable Reactance (Nexans Technical Data for OXY Project)

Table 2 – Cable Reactance @ 50Hz

Conductor area

(mm2)

Cable Reactance (Ω/km)

Cable Type Codes

H1 H3 H4 H5 H8 L1 L2 L4 L5

2.5 - - - - - 0.158 0.093 0.0892 -

4 - - - - - 0.148 0.086 0.0833 -

6 - - - - - 0.143 0.084 0.0783 -

10 0.138 - - - - 0.134 0.079 - -

16 0.130 0.136 0.113 - - 0.125 0.0753 0.0683 -

25 0.123 0.128 0.106 - 0.179 0.119 0.0754 - -

35 0.118 0.123 0.102 - 0.174 0.117 0.0734 0.0650 -

50 0.114 0.119 0.099 - 0.170 0.114 0.0731 - -

70 0.109 0.113 0.095 - 0.164 0.111 0.0709 - -

95 0.105 0.109 0.091 - 0.159 0.107 0.0694 0.0625 0.0817

120 0.102 0.105 0.088 - 0.155 0.105 0.0691 0.0608 -

150 0.0987 0.102 0.086 - 0.153 0.104 0.0703 - -

185 0.0967 0.101 0.084 - 0.151 0.104 0.0707 - -

240 0.0935 0.096 0.081 - 0.147 0.101 0.0697 - -

300 0.0934 0.095 - 0.118 - 0.100 - - -

400 - 0.093 - - - 0.100 - - -

500 - 0.090 - - - 0.099 - - -

630 0.0879 0.088 - - - 0.097 - - -

Page 20: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 20 of 21

Page 20 of 21

4.3 Cable Current Rating (Nexans Technical Data for OXY Project)

Table 3 – Cable Current Ratings / Ampacity @ 45oC Ambient

Conductor area

(mm2)

Current Rating (A) Conductor area

(mm2)

Current Rating (A)

1 Core 3 Core 1 Core 3 Core

2.5 28 20 95 276 193

4 38 27 120 319 223

6 49 34 150 367 257

10 68 47 185 418 293

16 91 63 240 492 344

25 120 84 300 565 -

35 148 103 400 677 -

50 184 129 500 778 -

70 228 159 630 899 -

4.4 Cable Short Circuit Rating (Nexans Technical Data for OXY Project)

Table 4 – Cable Short Circuit Ratings @ t = 1 Second

Conductor area (mm2)

Short Circuit Rating (kA)

Conductor area (mm2)

Short Circuit Rating (kA)

2.5 0.365 95 13.9

4 0.583 120 17.5

6 0.875 150 21.9

10 1.46 185 27.0

16 2.33 240 35.0

25 3.65 300 43.7

35 5.10 400 58.3

50 7.29 500 72.9

70 10.2 630 91.9

Page 21: Electrical Cable Sizing(2)

ELECTRCIAL CABLE SIZING Page 21 of 21

Page 21 of 21

5.0 CONCLUSION

For cable sizing, the following point shall be considered:

o Current Rating

Correction of the Cable current ampacity shall be more than full current

o Voltage drop

Calculated voltage drop value shall be less than project requirement

o Thermal short circuit capacity

Calculated short circuit value shall be more than system’s short circuit rating

The largest cable size shall be used based on the above point.

6.0 APPENDIES

Appendix A - Draka Cable Data

Appendix B – Table 43A (IEE Wiring Regulation)

Appendix C – Table 4B3 (IEE Wiring Regulation)

Appendix D – Table 4C1 & 4C2 (IEE Wiring Regulation)

Appendix E – Table 52-E4 (IEC 60364-5-523)

Appendix F - Table 52-E5 (IEC 60364-5-523)

Appendix G – Tables of cable sizing