29-01-2013, 02:05 PM
Transmission lines parameters
[attachment=48725]
Constants of transmission lines
A transmission line has resistance, inductance and capacitance uniformly distributed along the whole length of the line.
Resistance: it is the opposition of line conductors to current flow. The resistance is distributed uniformly along the whole length of the line.
Inductance: when an A.C flows through a conductor a changing flux is set up which links the conductor. due to this flux linkages conductor possesses inductance.
Classification of overhead transmission lines
Short transmission lines:
when the length of an overhead transmission line is up to about 50km and line voltage is comparatively low(<20kv) it is usually considered as a short transmission line.
due to smaller length and low voltages capacitance effect are small and can be neglected.
So in the performance of short transmission lines only resistance and inductance of the line are taken .
Medium transmission lines:
when the length of overhead transmission line is about 50-150km and line voltage is moderately high
(>20kv <100kv) it is considered as a medium transmission line.
Due to sufficient length and voltage capacitance effects are taken in account.
Performance of single phase short transmission lines
As earlier said the effects of capacitance are neglected
for short transmission lines. The equivalent circuit of short transmission are as
[attachment=48725]
Constants of transmission lines
A transmission line has resistance, inductance and capacitance uniformly distributed along the whole length of the line.
Resistance: it is the opposition of line conductors to current flow. The resistance is distributed uniformly along the whole length of the line.
Inductance: when an A.C flows through a conductor a changing flux is set up which links the conductor. due to this flux linkages conductor possesses inductance.
Classification of overhead transmission lines
Short transmission lines:
when the length of an overhead transmission line is up to about 50km and line voltage is comparatively low(<20kv) it is usually considered as a short transmission line.
due to smaller length and low voltages capacitance effect are small and can be neglected.
So in the performance of short transmission lines only resistance and inductance of the line are taken .
Medium transmission lines:
when the length of overhead transmission line is about 50-150km and line voltage is moderately high
(>20kv <100kv) it is considered as a medium transmission line.
Due to sufficient length and voltage capacitance effects are taken in account.
Performance of single phase short transmission lines
As earlier said the effects of capacitance are neglected
for short transmission lines. The equivalent circuit of short transmission are as