Grading of cables Definitions of Grading of cables There is unequal stress distribution in cable is undesirable for the following reasons: Insulation of greater thickness is required which increases the cable size. Unequal stress distribution may leads to the breakdown of insulation. To overcome this drawbacks it is necessary to have a uniform stress distribution … Read more
Underground cables Underground cables are used to transmit or distribute electric power. Mainly overhead system or underground system are used to transmit or distribute electric power. An underground cable essentially consists of one or more conductors covered with suitable insulation and surrounded by a protecting cover. undergrounds cables has many advantages compared to overhead system … Read more
Long Transmission Line Lines having length more than 200 km are called long transmission line. As the line constants of the transmission line are uniformly distributed over the entire length of the line . However ,reasonable accuracy can be obtained in line calculations for short and medium transmission lines by considering these constants as lumped. … Read more
Primary Distribution system Primary distribution operates at the high voltage such as (3.3,6.6 and 11 KV).Primary distribution is usually carried out by 3-phase,3-wire system.Electric power from the generating station is transmitted through extra high tension transmission lines at voltage from 33 to 765 kv,to the substations.At the substations called secondary substations the voltage is stepped … Read more
Comparison between DC and AC system for transmission and distribution Transmission of electric power by high voltage dc system is superior to that by high voltage ac system in many respects. DC system requires only two conductors for transmission and it is also possible to transmit the power through only one conductor by using earth … Read more
Substation Introduction Substation receives the energy transmitted at high voltage from the generating stations and reduces the voltage to a value appropriate for local distribution and also provides facilities for switching. Substation are mainly of switching and converting.In switching substation different connections between various transmission lines are made.Whereas in converting substations converts ac into dc … Read more
Three-Wire DC Distribution System When the voltage is increased the efficiency of the transmission line increases and the cost of conductor material in feeder cables gets reduced but in case of dc system it is not possible to change the voltage between feeders and distributors without using rotating machinery which is undesirable,so the feeders and … Read more
Skin Effect The distribution of current over the cross section of the conductor is uniform for dc only.An alternating current flowing through a conductor does not distribute uniformly but tends to concentrate near the surface of the conductor.In case of an ac system no current flows through the core and the entire current is concentrated … Read more
Bundled conductors Transmission of large amounts of power over long distances,can be accomplished most economically by using extra high voltage(EHV).An increase in transmission voltage results in reduction of electrical losses,increase in transmission efficiency,improvement of voltage regulation and reduction in conductor material requirement.At the high voltage above 300Kv ,a round single conductor per phase is used,corona … Read more
what is Transposition of lines? Transmission line transmits bulk power at relatively higher voltages.These lines gives rises to electromagnetic and electrostatic fields of sufficient magnitudes which induces currents and voltages in the neighboring telephone lines.The currents so induced are superimposed on the true speech currents in the neighboring telephone wires and set up distortion,while the … Read more