Negative sequence directional element

[johndaniel]

Hello Folks,

I am new to the field of power system protection. I am working on a project where I have to calculate the values of 'Negative sequence directional element' for a radial system. I've successfully calculated the values of various parameters like pick up current, forward and reverse threshold but finding the positive sequence line impedance angle is troubling me. I have Z bus matrix for the line impedances between two buses. I have uploaded image of the single line diagram of the system.Does anybody have any idea how to calculate this?

Thanks

 

[davidbeach]

What type of relay? What is the impedance of a line section?

 

[johndaniel]

We are suing SEL 351S relay. They have not given any impedance as such what they have given is Z bus matrices between bus 800-802, 802-803,802-804.....to 806-807.

 

[davidbeach]

How does the Z-bus matrix differ from a table of impedances?

 

[Hector04]

Hi, By overlapping , you open the first line CB1 and CB2 then , "forward " and " backward " , then you determine the coordination ansi50 / 51 for each each given a value of negative sequence that is tolerable. In my review Appropriate value I2 is the one Who is not Reflected in the secondary of the transformer (in Dy1 for example) or in the case of Determining the voltage (U2 ) IEC 61000 2% or standard IEEE 1159 2%(less accurate ) .