Wood Pole Overhead Lines
Concentrating on the mechanical aspects of distribution wood pole lines, this informative text includes coverage of live line working, environmental influences, climate change and international standards.
TABLE OF CONTENTS Wood Pole Overhead Lines
8.8: Reactance
8.8 Reactance
8.8.1 General
Understanding the behaviour of any system that includes variable currents in a conductor, either as an alternating current or as transients, involves some knowledge of the reactance of the circuits. The intention here is to give a brief introduction to methods of calculating the inductive and capacitative reactances related to overhead conductors in simple configurations. This is not meant to be an exhaustive treatment.
8.8.2 Inductive reactance
The calculation of reactance is simplified if it is to be split into two sources:
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that due to magnetic flux within a radius of 0.3 m, including the internal reactance within the conductor ( X a)
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that due to the flux between 0.3 m radius and the centre of the equivalent return conductor (X d).
The sum of the two terms ( X a + X d) is the inductive reactance of the conductor under normal load conditions. The values X a and X d are also used in calculating the zero sequence impedance (under fault conditions).
The value of X a is an inherent electrical property of the conductor (allowing for the fact that the flux out to 0.3 m is included). The value of X d, however, depends on the spacing of the conductors and is unrelated to the conductor size. This is an important difference.
8.8.2.1 Calculation of X a
This calculation is aided by using the factor geometric mean radius (GMR), which represents the radius of an...
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