ABSTRACT
Once the complicated network of power system is formed, the performance of the system has to be analyzed under load condition and also upon the occurrence of the fault. To analyze the system a simplified diagram is to be prepared using the various system components connected to the system. This is called single-line diagram, which provides significant information. From the single-line diagram, the reactance diagram is formed. Since an electrical system/network operates at different voltage level taking the advantage of transformer as per requirement, to calculate various operating parameters per unit representation is required. Choice of the voltage level required for transmission and distribution of electricity and how selection of frequency came into effect are mentioned in this chapter. Continuous changes to meet the requirement of the increased demand and the uninterrupted power supply necessitated continuous search of suitable cost-effective conductive material for bare overhead conductors, which is oldest and exists till today. The high temperature low sag conductor, which is a truly interconnected network, for transmission and distribution is gradually entering in place of conventional aluminum conductor steel reinforced ACSR conductor. In the early days of the transmission of electric power the conductors were usually copper, but aluminum conductors have completely replaced copper for overhead lines because of the much lower cost and lighter weight of aluminum conductors compared with copper conductors of the same resistance. Options are being explored to increase the transmission capacity with adequacy to increase the voltage which is going up and up from 132 to 220 to 400 KV and more. Nowadays modern micro-grids have been part of the grid that can be regarded as a controlled entity within the power system and can be operated as a single aggregated load.
