Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Comparison of Conductor Material in Underground Electric System
Underground Electric Transmission System
The system of electric power transmission uses underground cables for transmitting the electric power from the generating station to the consumers is known as underground electric transmission system.
Underground cables have low visibility and are not affected by bad weather. However, the cost of these cables is comparatively high and their laying process is also time consuming.
Types of Underground Transmission System
Based on the type of supply (i.e. AC or DC) and the number of conductors used, the underground electric transmission system can be classified into the following types −
Underground DC System
- Two-Wire DC System
- Two-Wire DC System with Mid-Point Earthed
- Three-Wire DC System
Underground 1-Phase AC System
- 1-Phase Two-Wire AC System
- 1-Phase Two-Wire with Mid-Point Earthed
- 1-Phase Three-Wire AC System
Underground 2-Phase AC System
- 2-Phase Three-Wire AC System
- 2-Phase Four-Wire AC System
Underground 3-Phase AC System
- 3-Phase Three-Wire AC System
- 3-Phase Four-Wire AC System
Comparison of Conductor Material in Underground Systems of Transmission
In underground system, if the electric power is transmitted using the multi-core belted type cables, then the chief electric stress on the insulation is between conductors. Therefore, under such situations, the comparison of conductor material is made on the basis of maximum voltage between the conductors.
For comparing the conductor material needed in the underground electric power transmission system, the following assumptions are to be made −
The same amount of electric power (say P watts) is transmitted by each system.
The maximum voltage between conductors (say Vm) is the same in each system.
The length (say l meters) over which the electric power is transmitted remains the same in each case.
The line losses (say W watts) are the same in case of each system.
The table given below shows the ratio of conductor material required in any underground system with respect to the underground 2-wire DC system. Here, cos𝜙 is the power factor of the load in AC System.
| System | Volume of Conductor Material (Same maximum voltage between conductors) |
|---|---|
| DC System | |
| (i) 2-wire system | 1 |
| (ii) 2-wire with mid-point earthed | 1 |
| (iii) 3-wire system | 1.25 |
| Single-Phase AC System | |
| (i) 1-phase 2-wire system | $\mathrm{\frac{2}{cos^{2}\, \phi }}$ |
| (ii) 1-phase 2-wire with mid-point earthed | $\mathrm{\frac{2}{cos^{2}\, \phi }}$ |
| (iii) 1-phase 3-wire system | $\mathrm{\frac{2.5}{cos^{2}\, \phi }}$ |
| Two-Phase AC System | |
| (i) 2-phase 3-wire system | $\mathrm{\frac{2.914}{cos^{2}\, \phi }}$ |
| (ii) 2-phase 4-wire system | $\mathrm{\frac{2}{cos^{2}\, \phi }}$ |
| Three-Phase AC System | |
| (i) 3-phase 3-wire system | $\mathrm{\frac{1.5}{cos^{2}\, \phi }}$ |
| (ii) 3-phase 4-wire system | $\mathrm{\frac{1.75}{cos^{2}\, \phi }}$ |
242 Views
