The distances between conductors of transmission lines are big. Therefore the inductivity is big also and the ratio R/X is small. The distances between conductors of cables in distribution systems are very small and their conductor square could be equal to that of transmission lines. Therefore the inductivity is small also and the ratio R/X is bigger than that of transmission lines.
In transmission systems the distance between conductors is much greater than in the distribution, therefore, the flux linkages between the conducting phases are greater, so that the external component of the line inductance is much higher in these systems than in the distribution; for this causes inductive reactance transmission line is three or more times higher than resistance making its contribution to the modular impedance value negligible as well as the phase angle feeding. In the distribution systems external inductance component is small and its reactance value is comparable with the resistance, which is why a significant error is introduced by not taking into account the resistance to calculate these systems.
can any one tell me the typical value of r/x ratio of distribution lines and high voltage transmission lines
Dear Srikanth,
From the conceptual point of view any transmission line has four parameters per meter. It has an inductance L .of its conductors , a resistance R of its conductors, a capacitance C between its conductors and a leakage conductance G between its conductors. The value of these parameters depends on the construction of the the transmission line; the cross section of its conductors, the material of its conductors, the distance between its conductors and the insulator between its conductors. The transmission line used to transmit electric power works at much higher voltage than the the distribution wire. There fore the distance between the wires is made much larger than the distribution line which leads to much higher magnetic energy storage and consequently its inductance per unit length will be higher.
Concerning the resistance which depends on the cross section and material type it will be comparable for the same carrying capability because the cross section's sized to limit the ohmic losses.
Accordingly the L/R ratio of the transmission line will be higher than that of the distribution line for the same current ratings.
OTHER WAY EXPRESSED, ONE CAN CONSIDER X IS DOMINANT IN TRANSMISSION LINES COMPARED TO THE RESISTANCE AND THE OPPOSITE IS TRUE FOR THE DISTRIBUTION LINES.
wish you success
I think, it takes place mainly due to predominate of per unit resistances for lower rated voltage systems (distribution systems).
In the same context, can anyone suggest me numerical value of inductance of a small distribution line.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Inorganic Materials
- Ceramics
- Glass