Correct Answer - Option 1 : Inductance
Self GMD or GMR:
- Self GMD is also called GMR. GMR stands for Geometrical Mean Radius.
- GMR is calculated for each phase separately.
- self-GMD of a conductor depends upon the size and shape of the conductor
- GMR is independent of the spacing between the conductors.
GMD:
- GMD stands for Geometrical Mean Distance.
- It is the equivalent distance between conductors.
- GMD depends only upon the spacing
- GMD comes into the picture when there are two or more conductors per phase.
The inductance of the single-phase two-wire line is
\(L = \frac{{{\mu _0}}}{\pi } \times \ln \left( {\frac{{GMD}}{{GMR}}} \right) = \frac{{{\mu _0}}}{\pi } \times \ln \frac{D}{{r'}}\) H/m
GMD = Mutual Geometric Mean Distance = D
GMR = 0.7788r
r = Radius of the conductor
The capacitance between two conductors is
\({C_{ab}} = \frac{{\pi \varepsilon }}{{\ln \frac{D}{r}}}\) F/m
In the calculation of the capacitance, the inner radius of the conductor not considered
Therefore, The self GMD method is used to evaluate Inductance only.
- The inductance of the hollow conductor is less when compared to the solid conductor.
- A bundled conductor reduces the reactance of the electric transmission line.
- By making the bundle conductor, the geometric mean radius (GMR) of the conductor increased.
