Forces on Gantry-34

Annexure-2 Page-1

NEW MELLI GIS 220 KV SUBSTATION

S.N. 1

SHORT CIRCUIT CALCULATIONS

FOR MAX. TEMPERATURE AND NO WIND I.E. AT MINIMUM TENSION AS PER SAG TENSION CHARTS

Description

Notation/ Formula

Unit

Value

kV Arms kArms Sec. Hz

220 2000 40 1 50

m/sec

47 1 0.85 1.0 50 34 .3g

INPUT DATA AC System Data Rated Voltage, Vac Rated continuous current, Ic Rated short time current, Isc Duration of short time current, t AC system frequency, f Site Data Wind speed, v Risk Coefft., K1 Terrain Roughness Factor, K2 Topography factor, K3 Design ambient temperature, Td Distance between supports, L Horizontal seismic coefficient, hsc

Taken from IS-875 Pt-3

ºC m

Conductor Data Type Number of sub conductors/phase Mass per Unit length of one conductor Weight of Spacer Distance of Spacers No. of Spacers Spacer Weight / Conductor/ Meter Mass per Unit length of one conductor with spacer

kg/m

ACSR Moose 2 1.57 1.6 2.5 12 0.32 1.92

Cross Section Area Diameter Young's modulus, E

sq mm mm Kg/cm2 N/m2

570 31.05 5.40E+05 5.30E+10

Min creepage Distance between discs Conductor temp. at the begining of short circuit, Ti Conductor temp. at the end of short circuit, Tf Type of span (=1 for single span beam, =2 for double span beam)

mm mm ºC ºC

6125.00 146 85 200 2

Distance between phase conductors, A Length of insulator chain No. of discs Tension on Conductor at maximum temperature 85 deg and no wind load (as per sag tension charts)

M M kg

4.50 3.114 15 564.04

N

9332.35

as ls

M mm mm m

1.5 250 2500

Characteristic Electromagnetic Load per unit Length on flexible conductor in Three phase system pi Permeabaility in free space

F' = μo/2*π X 0.75X (Ik)2/a X lc/l

N/m

3 Ph short circuit

Ik

A

40000

Distance between phases Conductor span Clear Condcutor length

a l lc

M M M

4.50 34.00 26.27

Hence

F'

N/m

41.21

Ratio of Electromagnetic force under short circuit ϒ = F'/ (n*m's *gn) conditions to the gravitational force on a conductor where Number of sub-conductors n Mass per unit length of one sub-conductor m's

Kg/M

2 1.92

Acceleration of Gravity

gn

m/s2

9.81

Hence

r

Girder width Distance between subconductors Distance between spacers Length of Turn Buckle a.

b.

n kg/m kg M

π μo =4π*10-7

3.14 1.25714E-06

1.094

Annexure-2 Page-2

NEW MELLI GIS 220 KV SUBSTATION SHORT CIRCUIT CALCULATIONS

FOR MAX. TEMPERATURE AND NO WIND I.E. AT MINIMUM TENSION AS PER SAG TENSION CHARTS

Description

Notation/ Formula

Unit

Value

c.

Direction of resulting Force exerted on the conductor

δ1=arctan(ϒ)

rad

0.8303

deg

47.5508

d.

Equivalent static conductor sag at midspan

S.N.

2

where Static Tensile Force in flexible conductor

bc= n* msc*gn * l / (8*Fst) Fst=

M N

9332.35

Hence

bc=

M

0.5833

e.

Period of Conductor oscillations

T=2π√(0.8/(bc/gn)

s

1.3709

f.

Resulting period of conductor oscillation during short circuit current flow

Tres= T/(√√(1+ϒ 2) (1-(π2/64)*(δ1/90)2 s

1.1767

g

Actual Youngs Modulus

Es=E*((0.3+0.7*sin(Fst/(n*As*бfin)*90)) for Fst/(n*As)