⚡💡UNDERGROUND AND OVERHEAD CABLES IN TRANSMISSION LINES ⚡💡
♂️INTRODUCTION
⚡the Transmission and distribution of electrical power can be with the help of overhead transmission lines or by underground cables it has been mentioned that in thickly populated areas like towns and cities the use of overhead lines is not practicable in such cases electrical energy is transmitted and distributed with the help of underground cables. in its basic form and underground cable is a conductor provided with proper insulation as the voltage level increases the cost of the insulation increases rapidly and does the use of underground cable is restricted to low and medium voltage distribution.
✏️UNDERGROUND CABLES
⚡there are generally two types of cables they are underground cables and overhead cables.First we are going to discuss about underground cables:
👉the interruptions due to lightning Storms and other weather conditions are eliminated.
👉the cost of the cable is extremely high.
👉it requires less maintenance
👉the cables are insulated and hence very safe.
👉the size of the cable is high.
👉the insulation cost is very high.
👉long distance transmission is not possible as laying of cables is costly difficult and complicated.
👉the beauty of cities and towns gets maintained.
👉the voltage drop is less.
👉the possibility of accidents is less.
✏️OVERHEAD CABLES
⚡next we are going to discuss about overhead lines:
👉 the interruptions due to lightning Storms and other weather conditions are possible.
👉the conductors are less expensive.
👉it requires more maintenance.
👉the conductors are there and not insulated which is unsafe.
👉the size of the conductor is less.
👉no insulation cost as a itself access an insulation.
👉the long distance transmission is possible.
👉the beauty of cities and towns get affected as trees are required to be cut.
👉the voltage drop is more.
👉the possibility of accidents is more.
✏️comparison of underground cables and overhead lines✏️
💁♂️ compared to overhead lines the underground cables are the following advantages
1) it ensures non interrupted continuity of supply the possibility supply interruptions due to lightning Storms and other weather conditions are eliminated because of underground cables.
2) it requires less maintenance.
3) the accidents caused due to breakage of overhead line conductors are eliminated due to use of underground cables.
4) the voltage drop in the underground cable is less.
5) the life of underground cable is long compared to the overhead lines
6) the beauty of cities and towns get maintained due to the underground network of cables.
7) the overhead lines used bare conductors which is unsafe in thickly populated areas and from safety point of view the underground cables are more advantages advantageous.
⚡the only drawback of the underground cables are the extremely high initial cost and insulation problems at high voltages in India the big cities have adopted the system of underground cables for the Transmission and distribution purpose .
⚡Thus the use of underground cables is mainly for the distribution of an electrical power it low and medium voltages. its use is almost compulsory at the location where use of overhead lines is not practicable due to the safety reasons such as congested urban areas crossing over Wide Road near gas plants and Refineries near substation etc.
1) long distance transmission is possible only by means of overhead lines
2) the conductor in overhead lines is less expensive compared to that of underground cables.
3) the size of the conductor in overhead lines is less than that of underground cables due to the good heat dissipation in overhead lines.
4) the installation cost is very less as the air itself acts as an insulation between the conductors the gas or oil is not required for the overhead lines for high voltage level spacing in air can be easily adjusted in case of overhead lines to obtain the proper installation insulation.
5) the election cost is much less for the overhead lines the underground cable laying is difficult and very much complicated depending upon our requirement we can use either the underground or the overhead transmission system.
⚡✨REQUIREMENTS OF THE CABLES⚡
✏️an underground cable can be defined as the group of individual insulated one or more conductors which is put together and finally provided with the number of layers of insulation to keep proper mechanical support.
✏️the conductors used in the cables are usually aluminium or annealed copper wire insulation is commonly PVC or other chemical compositions many types of cables are available depending upon the nature of conductors number of conductors type of insulation used except the basic necessary requirements of the cables are :
1) the size of the conductor used must be such that it should carry the specific load without overheating and keeping the voltage drop well within the permissible limits.
2) at the voltage level for which cable sir design the insulation thickness must be proper so as to provide high degree of safety and reliability tree
3) the cables must be surrounded by number of layers of an additional insulation so as to give proper mechanical strength and protection. cables can withstand the rough use at the time of lay in them.
4) the materials used in the manufacturing of cables must be said that there is complete chemical and physical stability throughout
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