We have already discussed so many articles regarding some of the greater features of high voltage overhead transmission lines. Such as Transportation of Transmission Line, Skin effect of power lines etc. Today we are going to discuss another important feature of high voltage transmission lines which are the Corona Effect in High Voltage Transmission Line and the Electric and magnetic Field effect.
Corona Effect in High Voltage Transmission Line
Voltage up gradation of the existing lines results into increase in the surface gradient of the existing conductors which may be more than the corona onset gradient for the existing conductor configuration, thereby resulting in an escalation of radio noise, television noise, audible noise and corona loss.
Voltage up gradation of transmission lines Situated in regions with high density of rainfall, snowfall & local contaminations may pose a greater challenge with respect to the corona & its effects.
order to mitigate the increase in radio noise, television noise, audible, etc., it may be required to replace the existing Conductor with a larger inductor or bundled with another similar Conductor In such situations the mechanical assessment of the transmission line becomes more challenging.
since the existing structure loads will be much higher. The existing Structures may have to be reinforced or replaced.
Studies shall also be carried out to assess the adequacy of the present line hardware for operation at the higher voltage. Armor rods may go into Corona at the ends of the rods and be a source of radio and television noise.
The type of conductor clamps is also significant for Corona Effect in High Voltage Transmission Line . Replacement of standard hardware with corona-free hardware may be necessary for operation at the higher field levels.
Electric and magnetic Field in Transmission Line
Since, the strength of the electric & magnetic fields depends on both line voltage, line current and on conductor geometrical parameters, up gradation of an existing transmission line results into subsequent increase in the ground level electric and magnetic fields.
The electric field decreases rapidly with lateral distance from the line and is further reduced by grounded objects like trees, lamp posts, buildings & other structures. The magnetic field also decreases rapidly with lateral distance from the line.
The electric field decreases rapidly with lateral distance from the line and is further reduced by grounded objects like trees, lamp posts, buildings & other structures. The magnetic field also decreases rapidly with lateral distance from the line.
In cases where upgrading results in closer conductor spacing, the electric field near ground level is reduced due to the mutual partial cancellation of individual electric fields of the conductor.
As a result, it may not be necessary to Increase the height of the conductor due to voltage upgradations. In some cases, the right of way width may be increased to allow lower EMF fields at the edge of the right of way.
Live Line Maintenance in HV Line
Higher voltages require greater clearances for live working, and the upgrading may change work practices, or even make live working impossible. Increasing the voltage of a transmission line necessarily increases the minimum approach distance (MAD) that is required for live line working.
When contemplating modifications to an existing transmission line to make operation at a higher voltage technically feasible, it is appropriate to review the changes to determine if there are any low-cost modifications that could be employed to help facilitate live line working.
