Surge Impedance Loading or SIL

Surge Impedance Loading is a very essential parameter when it comes to the study of power systems as it is used in the prediction of maximum loading capacity of transmission lines. However before understanding SIL, we first need to have an idea of what is Surge Impedance (Zs). It can be defined in two ways … Read more

Ground Clearance of Different Transmission Lines

Indian Electricity Rule 1956, Clause No 77, mentions, the minimum distance between bottom conductor and ground of different overhead transmission lines. As per Indian Electricity Rule 1956, Clause No 77, the minimum distance between bottom conductor and ground of a 400KV transmission line is 8.84 meter. As per this clause, of IE 1956, minimum ground … Read more


Let us first go through some important terms which associated with the topic admittance. We all know that resistance (R) has only magnitude but no phase. We can say that it is the measure of opposition for the flow of current. In AC circuit; in addition to the resistance, two impeding mechanisms (inductance and capacitance) … Read more

Performance of Transmission Line

There are three main types of Overhead Transmission Lines: Short transmission line – The line length is up to 60 km and the line voltage is comparatively low less than 20KV. Medium transmission line – The line length is between 60 km to 160 km and the line voltage is between 20kV to 100kV. Long … Read more

ABCD Parameters of Transmission Line

A major section of power system engineering deals in the transmission of electrical power from one particular place (eg. generating station) to another like substations or distribution units with maximum efficiency. So it’s of substantial importance for power system engineers to be thorough with its mathematical modeling. Thus the entire transmission system can be simplified … Read more

Advantages of Bundled Conductors

What are Bundled Conductors? We can often see the transmission lines where instead of a single conductor per phase multiple conductors per phase are being used. A metallic structure called spacers groups the conductors of a phase. These spaces help to maintain a constant distance between the conductors throughout their length, avoid clashing of conductors … Read more

Sag in Overhead Conductor

What is Sag? Sag is defined as the different in level between points of supports and the lowest point on the conductor. Here AOB is the transmission line conductor. Two supports are at point A and at point B. AB is the horizontal line and from this horizontal line to point O, S is the … Read more

Bundled Conductors Used in Transmission Line

Single stranded conductors are used in transmission system usually up to 220 KV. But it is not possible to use single-stranded conductor for the voltage above 220 KV systems. For very high voltage system, hollow conductor can be used to optimize the flow of current through it. But erection and maintenance of hollow conductors in … Read more