9257M-100-CN-1621-002 Rev. A

RASGAS DOC NO. TPME DOC NO

LOC Disc Type Sr. No Sht Rev Project No. Unit Document

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RASGAS PROJECT NO. : RGCP-256 TPME PROJECT NO. : 9257M-100

NEW OPERATIONS OFFICE BUILDING (NOOB)

RASGAS CONTRACT Nº CT/RG16/G103/05 TECHNIP CONTRACT Nº 9257M

CALCULATION FOR LOW VOLTAGE CABLE SIZING

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CONTENTS

1. GENERAL ......................................................................................................................4

2. PURPOSE......................................................................................................................4

3. DEFINITIONS & ABBREVIATIONS ...............................................................................4

3.1 DEFINITIONS.....................................................................................................4

3.2 ABBREVIATIONS ..............................................................................................5

4. APPLICABLE CODES & STANDARDS.........................................................................6

4.1 RASGAS STANDARDS .....................................................................................6

4.2 PROJECT DOCUMENTS ..................................................................................6

4.3 INTERNATIONAL CODES AND STANDARDS .................................................6

5. ATOMOSPHERIC SERVICE CONDITIONS..................................................................7

6. ELECTRICAL SYSTEM DETAILS ................................................................................7

7. VOLTAGE GRADE OF CABLES ...................................................................................7

8. MINIMUM AND MAXIMUM CABLE SIZE ......................................................................7

9. CABLE INSTALLATION.................................................................................................7

10. SIZING CALCULATIONS...............................................................................................8

11. CABLE DATA.................................................................................................................8

11.1 CONTINUOUS CURRENT CARRYING AMPACITIES......................................8

11.2 CORRECTION FACTORs..................................................................................8

11.3 RESISTANCE AND REACTANCE OF CABLES ...............................................9

11.4 SHORT CIRCUIT withstand capacity.................................................................9

11.5 VOLTAGE DROP CALCULATION...................................................................11



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APPENDIX 1 - RESISTANCE AND REACTANCE OF CABLES (1 PAGE).................................13

APPENDIX 2 - SHORT CIRCUIT RATING OF CABLES (1 PAGE).............................................14

APPENDIX 3- CABLE SELECTION CHART FOR MOTOR AND POWER FEEDER (6 PAGES).....................................................................................................................................................15



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1. GENERAL

RasGas (RG) has awarded TECHNIP (TP) for the Front End Engineering & Design (FEED) of New Operations Office Building (NOOB) in Ras Laffan Industrial City, in the State of Qatar.

The objective of this Project is to carry out Engineering, Procurement and Construction of a New Operations Office Building located west of the existing RasGas plant fence in the area just south of the New Maintenance Workshop Building.

The building is required to provide a sufficient number of offices and auxiliary rooms required for the current RasGas site development incorporating operating plans for RL, RL II, RL III, He, and AKG.

Under the project, the FEED for the Building shall be carried out by Technip- Abu Dhabi, who is the FEED EPC CONTRACTOR for RG.

2. PURPOSE

This document defines the technical basis, parameters and criteria used for determining the required sizes of electrical Low Voltage Cables for the New Operation office building to be installed for Rasgas at state of Qatar.

3. DEFINITIONS & ABBREVIATIONS

3.1 DEFINITIONS

For the purpose of this document, the words and expressions listed below shall have the meanings assigned to them as follows:

PROJECT : NEW OPERATION OFFICE BUILDING (NOOB) COMPANY : RASGAS FEED CONTRACTOR

: TECHNIP France – Abu Dhabi, U.A.E.

EPC EPC CONTRACTOR who will carry out all the required



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CONTRACTOR : Detailed Engineering, Procurement , Installation / Commissioning under a separate EPIC CONTRACT to be assigned (Project Stage –II)

SUB- CONTRACTOR

: Entity, COMPANY or group of companies entrusted by the EPC CONTRACTOR to perform part of the PROJECT

VENDOR :

Means any and all persons, firms, partnerships, companies, bodies, entities or a combination thereof including Sub-VENDORs, who are providing Equipment, material and services to perform duties specified by EPC CONTRACTOR.

3.2 ABBREVIATIONS

For the purpose of this document, the words and expressions listed below shall have the meanings assigned to them as follows:

ABBREVIATION : FULL DESCRIPTION

AC : Alternating Current CB : Circuit breaker FLC : Full Load current EPC : Engineering Procurement and Construction FEED : Front End Engineering & Design Hz : Hertz IEC : International Electrotechnical Committee kA : Kilo ampere kV : Kilo Volts LV : Low Voltage MVA : Mega Volt Ampere NOOB : New Operation Office Building GSWA : Galvanised Steel Wire Armoured UPS : Uninterruptible Power Supply XLPE : Cross Linked Poly Ethylene



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4. APPLICABLE CODES & STANDARDS

4.1 RASGAS STANDARDS

Rasgas project specification indicated below shall form a part of this technical specification

Doc. No: Document Title

RGX-S-91-1380-003 : Electrical requirement for building RGX-S-91-1382-005 : Low Voltage cables

4.2 PROJECT DOCUMENTS

Doc.No Description

9257M-100-ACT-16-05 : Design basis memorandum 9257M-100-JSS-1600-001 : Specification for building electrical 9257M-100-JSS-1621-002 : Specification for LV Power and Control Cables 9257M-100-SP-1621-002 : Data sheet for LV cables

4.3 INTERNATIONAL CODES AND STANDARDS

The following codes and standards shall be applied. Any deviations or conflicts shall be reported in writing and shall require prior approval.

IEC 60364 Part 5-52 : Selection and erection of electrical equipment wiring system

IEC 60228 : Conductors of insulated cables

Should any conflict arise between the various codes and standards, the following ranking precedence shall apply. However, EPIC CONTRACTOR shall identify the conflict and bring it to the attention of COMPANY with suitable recommendation.

♦ Qatar National Standards.

♦ COMPANY engineering standards applicable to this project

♦ Other International Standards



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5. ATOMOSPHERIC SERVICE CONDITIONS

Atmospheric & site conditions are as follows

♦ Ambient Temperature : 49 °C Max / 4 ° C Min

♦ Relative Humidity : 90%

♦ Direct sun shine Temperature : 82 ° C

♦ Atmospheric conditions : Dusty, Sulphurous, Corrosive, as commonly encountered in petrochemical installations in close proximity to sea.

♦ Altitude : Less than 1000m

6. ELECTRICAL SYSTEM DETAILS

LV Supply Voltage 415V Frequency 50Hz System Earthing Solidly Earthed

7. VOLTAGE GRADE OF CABLES

♦ Low Voltage cables shall be rated for 600/1000 volts.

8. MINIMUM AND MAXIMUM CABLE SIZE

Minimum cross section of cable shall be 4 Sq.mm.

Maximum cross section of multicore cable shall be 185 Sq.mm.

Maximum cross section of single core cable shall be 630 Sq.mm. (Single core cable shall be used where 2 runs of 185 Sq.mm. multicore cables is not sufficient).

9. CABLE INSTALLATION

The methods of cable installation shall be as per “Design basis memorandum, 9257M-100-ACT-16-05” and “Specification for Building electrical, 9257M-100-JSS-1600-001”.



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10. SIZING CALCULATIONS

LV cables shall be sized in accordance with the following criteria and the relevant standards listed in this document.

♦ Short circuit withstand capacity for a specific duration.

♦ Admissible current ampacity of cables considering derating factors.

♦ Admissible voltage drop.

11. CABLE DATA

11.1 CONTINUOUS CURRENT CARRYING AMPACITIES

The current carrying capacities for XLPE multicore cables as per IEC 60364-5-52, Table A.52-5 and Table A52-12 are used for calculation with the following parameters

Ambient air temperature : 49°C

Ground thermal resistivity : 1.2°C.m/W

Ground temperature : 40°C

Depth of laying : 0.8m

Max. Conductor Operating temperature : 90°C

11.2 CORRECTION FACTORs

Tables A.52-14 to A.52-18 in IEC 60364 Part 5-52 give the various Correction Factors under different conditions like variation of Ground temperature, Soil thermal resistivity, grouping of cables and Variation in Ambient temperature.

Based on the installation conditions, the following derating factors have been considered.

For LV cables laid in ground as per IEC 60364-5-52

a Rating factor for ground temperature of 40°C (Table 52-15) Kt =0.85 b Rating factor for soil thermal resistivity of 2.5 °K.m/W (Table

52-16) Ks =1.00



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c Rating factor for direct burial at a depth of 0.8 metre (Table 52-16)

K1 =1.00

d Rating factor for grouping of cables (6 cables with 0.125m spacing) (Table 52-18)

Kg = 0.6

e Overall admissible ampacity correction factor Df = Kt X Ks X K1 X Kg = 0.51

For LV cables laid in ground as per IEC 60364-5-52

a Rating factor for ambient temperature of 49 °C (Table 52-14) Kt =0.82 b Rating factor for grouping of cables (7 cables touching) (Table

52-17) Ks =0.73

c Overall admissible ampacity correction factor Df = Kt X Kg = 0.6

11.3 RESISTANCE AND REACTANCE OF CABLES

The Appendix – 1 gives the resistance and reactance of various sizes of cables which is part of IEC 60228 and manufacturer’s data respectively.

11.4 SHORT CIRCUIT withstand capacity

MINIMUM CROSS SECTION OF CABLE, BASED ON SHORT CIRCUIT CURRENT

The cable short circuit current capacity is evaluated as

++

=βφβφ

0

122

2 logeSC TSKI

Where

Isc = short circuit current (r.m.s) in Amp T = duration of short-circuit in seconds

K = Constant for the material of conductor

S = area of conductor in mm²



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∅1 = final temperature in °C

∅0 = initial temperature in °C

β = reciprocal of the temperature coefficient of resistance of conductor in °C at 0°C

The constant K and β for copper cables and ∅1 and ∅0 for Copper / XLPE cables are:

K = 226 β = 234.5

∅1 = 250°C (for XLPE cable)

∅0 = 90°C (for XLPE cable)

On substituting the above values in the given formula, the short circuit currents for Copper, XLPE cables shall be given as:

TSI SC

×=

143

And minimum cross section shall be derived as follows,

143TIS SC ×=

Based on the above, the short circuit withstand of cables shall be calculated based on switchboard short circuit rating and fault clearing time as below:

Item Description Short Circuit Current

level (kA)

Short Circuit

Duration (sec)

Minimum Cable Size

(sq.mm)

415V incomer 80 0.5 400

Notes:

1) Short circuit current level means rated interrupted current of each switchgear

2) Short circuit duration is determined as follows:



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415V Incomer

= Relay (51) operating time + CB interrupting time + allowance

= 0.2 sec. (10 cycle) + 0.08 sec (4 cycle) + 0.2 sec. (10 cycle)

= 0.48 sec (0.5 sec selected for cable sizing)

The Copper, XLPE cable size required for various short circuit current and clearance times are tabulated in Appendix -2.

Incomer connected to transformer rated 1 MVA and above shall be connected through suitably rated busduct.

11.5 VOLTAGE DROP CALCULATION

ALLOWABLE VOLTAGE DROP

The following are the permissible voltage drop as per “Design basis memorandum, 9257M-100-ACT-16-05”.

Cable between transformer and switchgear fed by the transformer 0.5% Cable between switchgear and local distribution panels 1.0% Cable between LV switchgear and LV Motor 5.0% Cable between LV switchgear and LV Loads 4.0% Cable between switchgear and lighting panel fed by the switchgear 1.0% Cable between lighting panel and farthest lighting fitting fed by the lighting panel

4.0%

Outgoing feeders from AC UPS 4.0%

Transient voltage variations occurring during starting or re-acceleration of a motor or group of motors shall be limited to

♦ Not more than 15% from rated equipment voltages at equipment (motor) terminals for LV equipment.

♦ Not more than 10% from the rated voltages at switchgear bus bars.



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VOLTAGE DROP

( ) LIXSinCosRxn

V ...10003 ϕϕ +=∆ (For 3 phase loads)

Where

∆V = Voltage drop in volts (v) L = Length of cable in metres n = Number of cables running in parallel per phase R = Resistance in Ohm/km @50Hz X = Reactance in Ohm/km @ 50Hz l = Load current in Amps Cosϕ = Load Power factor

CABLE SELECTION

Breaker operated feeder cables shall be selected based on short circuit rating, Full Load Current (FLC) and permissible voltage drop.

Cable selection feeder chart for 415V motor feeder and power feeder is provided in Appendix-3.



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APPENDIX 1 - RESISTANCE AND REACTANCE OF CABLES (1 PAGE)

CALCULATION FOR ELECTRICAL LOW VOLTAGE CABLE SIZING

DOC. NO.: 9257M-100-CN-1621-002 REV. A Page 1 of 1

APPENDIX 1

RESISTANCE AND REACTANCE OF LV, XLPE CABLE:

Resistance (Ref. Table II, column-8 of IEC

60228)

Reactance at 50 Hz (Ref. Cable Manufacturers

catalogue)

R in ohm/km

Nominal area of

Conductor (mm2)

20°C 90°C (ref. Note 1)

mH/km ‘L’

Ohm/km ‘X’ (2)

2.5 7.41 9.50 - 0.105

4 4.61 5.91 - 0.098

6 3.08 3.95 - 0.094

10 1.83 2.35 - 0.088

16 1.15 1.47 0.118 0.084

25 0.727 0.93 0.112 0.083

35 0.524 0.67 0.107 0.081

50 0.387 0.50 0.104 0.080

70 0.268 0.34 0.101 0.079

95 0.193 0.25 0.098 0.077

120 0.153 0.20 0.096 0.077

150 0.124 0.16 0.096 0.077

185 0.0991 0.13 0.096 0.077

240 0.0754 0.10 0.094 0.077

300 0.0601 0.08 0.093 0.077

400 0.0470 0.06 0.093 0.076

500 0.0366 0.047 0.093 -

630 0.0283 0.036 0.090 -

800 0.0221 0.0283 0.092 -

Notes: 1) The temperature correction factor for copper conductor

=t+5.2345.254

(Ref. IEC 60 228, Cl. 6)

= 0.78 (t = for 90°C)

2) ‘X’ can be derived by the formula

X = L.2πf / 1000 (where f = 50Hz)



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APPENDIX 2 - SHORT CIRCUIT RATING OF CABLES (1 PAGE)

CALCULATION FOR ELECTRICAL LOW VOLTAGE CABLE SIZING

DOC. NO.: 9257M-100-CN-1621-002 REV. A Page 1 of 1

APPENDIX 2

SHORT CIRCUIT RATING OF CABLES The below chart is prepared based on the clause 9.2 of this document.

Short Circuit

current in ampere

Cu, XLPE cable Size in sq.mm for durations

0.01 sec.

0.025 sec.

0.050 sec.

0.100 sec.

0.200 sec.

0.250 sec.

0.500 sec.

1.000 sec.

80000 70 95 150 185 300 300 400 630

70000 50 95 120 185 240 300 400 500

60000 50 70 95 150 240 240 300 500

50000 50 70 95 120 185 185 300 400

40000 35 50 70 95 150 150 240 300

31500 25 35 50 70 120 120 185 240

25000 25 35 50 70 95 95 150 185

15000 16 25 25 35 50 70 95 120

10000 10 16 16 25 35 35 50 70

5000 6 6 10 16 16 25 25 35

2500 2.5 4 4 6 10 10 16 25



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APPENDIX 3- CABLE SELECTION CHART FOR MOTOR AND POWER FEEDER (6 PAGES)

9257M-100-CN-1621-002 Rev. A

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