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A, The Average Voltage of The Conductors Is Same And, Therefore, The Capacitance Is Also The

This document discusses the capacitance of transmission lines. It provides formulas to calculate capacitance per meter and capacitance per kilometer for a transmission line. It also gives an example calculation of capacitance and charging current per kilometer for a 132 kV transmission line with a conductor radius of 0.4 cm and mutual geometric mean distance of 2.015 meters between conductors.

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54 views1 page

A, The Average Voltage of The Conductors Is Same And, Therefore, The Capacitance Is Also The

This document discusses the capacitance of transmission lines. It provides formulas to calculate capacitance per meter and capacitance per kilometer for a transmission line. It also gives an example calculation of capacitance and charging current per kilometer for a 132 kV transmission line with a conductor radius of 0.4 cm and mutual geometric mean distance of 2.015 meters between conductors.

Uploaded by

ragupa
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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CAPACITANCE OF TRANSMISSION LINES 49

3
a abc
= ln
2 0 r
a GMD
= ln
2 0 r

a 2 0
or C= = F/metre (3.28)
Va ln GMD
r
Since the conductors b and c also occupy the same three positions as occupied by conductor
a, the average voltage of the conductors is same and, therefore, the capacitance is also the
same.
For a symmetrical spacing of the conductors,
a=b=c=h
2 0
C= (3.29)
h
ln
r
Example 3.1: Determine the capacitance and the charging current per km when the
transmission line of example 2.2 is operating at 132 kV.
Solution: The radius of conductor = 0.4 cm.
The mutual GMD of conductors, Dm = 2.015 metres.
2 0
Capacitance per phase per metre = F/metre
2.015
ln 10 2
0.4
10 9
= = 8.928 pF/metre
201.5
18 ln
0.4
= 8.928 1012 103 F/km
= 8.928 109 F/km
132 1000
The charging current = 8.928 109 314
3
= 0.2136 amp/km. Ans.

3.6 CAPACITANCE OF A DOUBLE CIRCUIT LINE

Normally two configurations of conductors are used: (i) hexagonal spacing, and (ii) flat vertical
spacing. First of all an expression of capacitance for hexagonal spacing is derived.
Hexagonal Spacing
Since the conductors of the same phase are connected in parallel the charge per unit length is
the same (Fig. 3.7). Also, because of the symmetrical arrangement the phases are balanced

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