hinljr00bua-ed00002a dc cable sizing calculation

8/19/2019 HINLJR00BUA-ED00002a Dc Cable Sizing Calculation

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TABLE DES MODIFICATIONS / MODIFICATIONS TABLE

REVETABLI

ESTABLISHED

VERIFIE

CHECKED

APPROUVE

APPROVED DATE MODIFICATIONS STAT.

A MURUGIAH DHS VIKAS 19.7.10 FIRST ISSUE. GFE


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CONTENTS

1 PURPOSE 4

2 REFERENCE DOCUMENT 4

2.1 REFERENCE STANDARDS 4

3 BASIC DATA 5

3.1 ENVIRONMENTAL CONDITIONS AND DESIGN CRITERIA 53.2 ELECTRICAL NETWORK DATA 5

4 TECHNICAL SPECIFICATION: 5

4.1 TYPE OF CABLE 5

4.2 INSTALLATION METHOD 6

5 CABLE SIZING METHOD 6

5.1 CURRENT CARRYING CAPACITY CRITERIA 6

5.2 SHORT CIRCUIT CRITERIA 8

5.3 VOLTAGE DROP CRITERIA 9

6 CIRCUIT BREAKER SELECTION 9

7 CALCULATION SHEET 9

8 ANNEXURE-I : CURRENT RATING, RESISTANCE & REACTANCE 10

9 ANNEUXRE-II : TEMPERATURE CORRECTION FACTOR 11

10 ANNEUXRE-III : GROUP RATING FACTORS 12

ATTACHMENT 1: CALCULATION SHEETS (220V DC SYSTEM)

ATTACHMENT 2: CALCULATION SHEETS (48V DC SYSTEM)


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1 PURPOSE

The purpose of the document is to define the basis of calculation of 220V & 48V DC Power Cable

Sizes for all the DC Distribution boards.

2 REFERENCE DOCUMENT

1 HINLJR20BUA-FD00001: 220 V DC System Single Line Diagram

2 HINLJR20BUA-FE00001: 220 V DC System Design memorandum

3 HINLJR20BUA-ED00001: 220 V DC System Power Balance

4 HINLJR20BUD-FD00001: 48 V DC System Single Line Diagram

5 HINLJR20BUD-FE00001: 48 V DC System Design memorandum

6 HINLJR20BUD-ED00001: 48 V DC System Power Balance

2.1 REFERENCE STANDARDS

1 IEC 60364-4-43 Electrical Instalations of Building – Protection Against Over Current

2 IEC 60364-5-52Electrical Instalations of Building – Selection and Erection of

Electrical Equipment Wiring System

3 IEC 60364-5-54

Selection and Erection of Electrical Equipment Earthing

Arrangements, Protective Conductors and Protective Bonding

Conductors

4 IEEE Std 241Recommended Practice For Electrical Power System In Commercial

Building

5 IS 1554 - Part 1PVC insulated (heavy duty) electric cables specification: For working

voltages upto and including 1 100 V


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3 BASIC DATA

3.1 ENVIRONMENTAL CONDITIONS AND DESIGN CRITERIA

In particular, the electrical and control equipment will be designed for the following ambient

conditions:

1 Pollution level Level III as per IS

2 Altitude


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4.2 INSTALLATION METHOD

Cable ..........................................................................Perforated Tray / Ladder Type

Single core cables ...............................................................Single layer laying with trefoil formation

[Refer Doc. HINLJR000BB FE00001]

Multi core cables.................................................................Multi layer laying (without exceeding the90% height of cable tray) and Cable

surfaces are touching [Refer Doc.

HINLJR000BB FE00001]

Buried cables ......................................................................Multi layer laying and Cable surfaces are

touching

5 CABLE SIZING METHOD

Cable sizing and selection is based on the following criteria:-

• Current carrying capacity under normal operating condition

• Current carrying capacity under short-circuit condition and

• Voltage drop

5.1 CURRENT CARRYING CAPACITY CRITERIA

The current carrying capacity of a cable de-rates due to

a) ambient temperature

b) accumulation of cable/installation of cable)

Such adaptation is done considering de-rating factors for ambient temperature and cable installation

d ib d h d


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Where, K θ = correction factor for ambient temperature (Annexure-III)

K 2 = Sun exposition factor which is

= 1 For cable screened from sun rays

= 0.8 For cable exposed to air with black sheath

= 0.9 For cable exposed to air with light colour sheath

K g = Cable installation de-rating factor (Annexure-IV)

The maximum permanent current (In) of a feeder is given as

In = SnU

Where Sn = Nominal apparent power of the feeder

U = System voltage (220V for 220V DC System)

Size of the cable selected shall ensure Id ≤ Iz

Where Iz is the rated current carrying capacity of the cable (Refer Annexure-I).

5.1.1 AMBIENT TEMPERATURE CORRECTION FACTOR

Temperature correction factor for an ambient temperature equal to 50

0

C, will be

K t = 0.9 (Annexure-III)

5.1.2 SUN EXPOSITION FACTOR


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5.1.3 GROUPING FACTOR

Multi core cables

As per the installation method adopted for multi core cables as per IEC 60364-5-52 (Annexure-IV),

the installation group rating factor shall be suitably selected.

Perforated trays, Laying configuration of 6 cables and 3 trays, K g = 0.71

5.2 SHORT CIRCUIT CRITERIA

The minimum cable cross-sectional area S is selected such that the maximum thermal stress in the

cable during short circuit does not reach the maximum permissible limit. The selection criteria is

given as (IEC 60364-4-43)

K 2 S2 ≥ I ² t

Where

i² t :- Energy let-through of the associated circuit breaker (As per

breaker manufacturer data)

K : - Cable constant which is given as

= ))()(1(ln)20(

20 i

i f cQθ β θ θ

θ β

+

−+×+× (IS 3043)

Where

Qc = Volumetric heat capacity of the conductor material in J/oC mm3

(See Annexure IV)

20θ = Electrical resistivity of conducting material at 20oC in Ω. mm. (See Annexure IV)

β = Reciprocal of temperature coefficient of resistivity of the conducting material at

0oC

iθ = Initial temperature of conductor inoC


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5.3 VOLTAGE DROP CRITERIA

The minimum cable cross-sectional area, S (in mm2) is calculated in such a way that the voltage drop

from the station service board / unit auxiliary board up to the consumer is less than or equal to 4%.

(IEC 60364-5-52)

Voltage drop

Δ V = (2 x In x R x L) / 1000

Where R = Resistance of the cable in Ω / Km, (Annexure-II)

In = Current in the feeder current A,

L = Length of cable in meter.

6 CIRCUIT BREAKER SELECTION

Circuit breakers rating is selected as per the connected load (i.e. maximum current in the feeder, I n)

so as to confirm that the rated current of the circuit breaker is greater than the maximum permanent

load in the feeder.

1. Thermal setting (Ith) of the circuit breaker/ current rating of CB is greater than or equal toconnected load, In.

2. Icu with or without association with upstream breaker ≥ Icu Upstream Board.

7 CALCULATION SHEET

Please refer to Attachment 1.


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8 ANNEXURE-I : CURRENT RATING, RESISTANCE & REACTANCE


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9 ANNEUXRE-II : TEMPERATURE CORRECTION FACTOR


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10 ANNEUXRE-III : GROUP RATING FACTORS


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ATTACHMENT 2 : CALCULATION SHEET (48V DC POWER CABLES)

FROM EQUIPMENT TO EQUIPMENTLOAD CURRENT

IN Amp

CABLE

TYPE

No. OF

RUNS

SELECTED

CABLE SIZE

RATED

CAPACITY OF

CABLE

CABLE

RESISTANCE

( Ω/Km)

LENGTH

(m)Kt Ks Kg

REQUIRED

CAPACITY OF

FEEDER (A)

PROTECTIVE

DEVICE RATING

(A)

DESIGNATION DESIGNATION (In) mm2 (Iz) R L (In / Kd) (Ir)

BATTERY BANK 1

48 V BATTERY BANK 48 V DCDB 48 - 15 XLPE-AL 1 2Cx35 1.11 0.0783 20 0.9 1 0.71 0.639 23.47 80 10.82 0.51 0.92 0.68



48V DCDB

48 V DCDB PLCC-1 48 - 2.7 XLPE-AL 1 2Cx2.5 9.5 0.0985 16 0.9 1 0.71 0.639 4.23 16 10.82 0.099 1 0.84



48 V DCDB PLCC4-Future 48 -

Kd = (Kt x

Ks x Kg)

Voltage

[V]

Consumption/O

utput Power

[W]

PERMISSIBLE

VOLTAGE

DROP (Vr)

RUNNING

VOLTAGE

DROP (Vpr)

K2S2

(kA2s)

LET-

THROUGH

(kA2s)

sheet 1 of 1

hinljr00bua-ed00002a dc cable sizing calculation

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