400kv Line Characteristic

Don't you think you would learn more if you did your own homework!

You go back to your textbook, . . find the right chapter and page . . . and figure it out.

I am assuming you are still in "school" . . . and have to do your own homework

If you are not in school, but working somewhere with 400kV lines, how did you ever get the job?

Any Voltage Transmission line Characteristic or surge impedance dose not depends on the transmission line length but depends on its square root of ratio L/C in Ohms. Where L and C are inductance and capacitance respectively of the line.

The question on characteristic impedance of a transmission Line is very important to know.The Characteristic impedance's has other names such as surge impedance, Natural impedance and Nominal impedance. Generally designated as Zo. It has value in 380V, 3-phase system around 480Ohms and 380Kv, 4conductors per phase has around 208 Ohms. This having units of Ohms but dose not make any power loss. This is used in Power System analysis and design in MS degree course for designing of a new transmission line. It has influence in two things 1. SIL( Surge Impedance Load) or power capacity loading or sending of power on a transmission line is given by SIL = V*V/(Sqr(L/C)). where L & C per unit length inductance & capacitance respectively and dose not depend on the material of conductor but depends on the configuration of the 3-phase conductors laid on the transmission Tower. 2. It also has influence on the reflection of the surge voltage( created due to switching of a line) decreasing or building up voltage.That is why when a transmission line joined by other transmission line the both should have same Zo otherwise creates problem reflection.

Similarly in communication cables such as CCTV system its cable( RG6 or RG11)has Nominal impedance or natural impedance values is designated by 75Ohms generally. If this cable is connected to BNC connector or monitor. Then cable, BNC connector and Monitor should have same impedance otherwise signal reflection will take place and picture seen on the screen will be poor.

THERE IS NO CHARACTERISTIC IMPEDANCE FOR ANY LINE. You need to know the conductor length in each phase, size and material of conductor and configuration of conductors i.e. spacing between the three phases. Please refer to any text book on overhead lines for the formulae.

Sounds to me like you know just as little about characteristics as does Nikrdesh Soni. Yes, do go back to your test book.

Dear Mr. Learner42 & Olihwi

I think both of you were absent in the class when TRANSMISSION LINES STEADY STATE OPERATION lecture was in progress. Because, your questions are being represented that you are not present in the class..

Anyhow, I will help you that please buy any power system analysis test book or the best test Book is" Power System Analysis and Design" with personal computer applications BY

J. Duccan Glover / Mulukunta Sarma: Northeaster University

PWS Publisher; Boston; USA

ISBN 0-534-07860-5:

All your doubts material is available in above mentioned Book in CHAPTER-6: "Transmission Lines, Steady - State Operation"

In chapter-6, Equation 6.4.5 states as The characteristic impedance Zc = ( L/C)^.5, commonly called surge impedance for a lossless line, is pure real, that is resistive.

Where L is inductance per unit length & C is capacitance per unit length. So Ratio L/C cancels the per unit length. That indicates the characteristic impedance does not depend on length but on L & C values.

I have 6 books in my shelf on Power system Analysis and design.

However, statement of Mr. Olihwi " Yes, do go back to your test book".

Please note that at present that time Text book is not available with me now as I studied in 1970(Just estimate your age) and I passed my Engineering in 1972.

Thank you sir for reminding my college life