Zero-sequence voltage - Shorebrook PE Power Exam Problems 66 and 62

[akyip]

Hi guys,

On Shorebrook PE Power Exam problem 66 solution, where does the formula (Ca + a^2 Cb + a Cc)/(Ca + Cb + Cc) come from when calculating the zero-sequence voltage En in the grounded Y system? Is there an explanation behind this formula?

Can this same formula also be applied to the ungrounded delta zero-sequence voltage En in Shorebrook Problem 62?

Thanks for any input! I'm just trying to understand this, since I haven't seen this in other practice PE exams or materials...

 

[Orchid PE]

On Shorebrook PE Power Exam problem 66 solution, where does the formula (Ca + a^2 Cb + a Cc)/(Ca + Cb + Cc) come from when calculating the zero-sequence voltage En in the grounded Y system? Is there an explanation behind this formula?

No idea. In the very unlikely event you come across this problem, guess and move on lol! Unless someone else can explain it.

Can this same formula also be applied to the ungrounded delta zero-sequence voltage En in Shorebrook Problem 62?

No. The first problem was relating to the capacitance of the lines. This second problem is merely a conceptual problem to make sure you understand symmetrical components and what the different quantities can tell you about the system.