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2. What are the limitations of HVAC transmission ?
EHV transmission lines are used to transmit large blocks of power over long distances.
It is used to supply power in those areas having large fuel shortage
Following factors are needed to be considered while designing EHV transmission line
1) Large cost is needed for converter substations.
Following factors are considered while designing of EHV lines
Method of Earthing : EHV lines are need to have solid permanent connection with ground. This allows the user to use lower rated lighting arresters.
Voltage level : Voltage level selection depends on the future good growth, loading level of transmission line.
Conductor : Transmission line conductors are selected depending on :
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Surge Impedance Loading Formula |
Z and Y are series impedance and shunt admittance per Km respectively.
Transmission loss : It need to be considered at varying load factors
Right of Ways (RoW) : These are based on the voltage of transmission line, cost required for Rows, safety level and environmental factors etc.
Reliability : Reliability level should be as large as possible to ensure each customer have access to electricity.
Voltage regulations : Keep as possible as low voltage regulation.
Insulation co-ordination : Proper insulation co-ordination results into reliable operation of transmission line, less damage of equipments etc.
Radio : interferences are need to be minimum.
Insulator failure : Insulator can easily operate at normal voltage level. During the operation due weather effects insulator developes flashover cracks on the surface. Due this during flashover insulator may get damaged. To have proper operation insulator maintenance should be done regularly.
(2) For erection of transmission line, same times trees are need to cut.
(3) Also during erection of tower, there is a need of digging the earth for tower footing which affects the stability of soil near it.
(4) Soil erosion is a major problem due transmission line erection.
(5) Largest climate change occurs due to energy loss during electricity transmission.
(6) Restrictions on land use : Building and structures are not permitted in transmission line areas due to electrical safety.
In bundled conductor, two or more strands are used in one phase. These are mainly used in system having voltages larger than 230 kV.
Due to bundling of conductors, reactance of bundle conductor is reduced because of self GMD which helps to transmit larger /maximum power.
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