symmetrical components

[Emadshaaban1987]

Dear ALL

I have difficults to clearly understand fault and their components , Can you please correct my thoughts about the symmetrical components

Earth fault current is created because by Zero sequence currents !
Current unbalance create negative sequence components !

What is different between earth fault VS zero sequence ? can the current unbalance create negative sequence
component?

 

[cuky2000]

. Yes, an unbalance current creates a negative sequence of components. Only In a balanced system, there is no negative or zero-sequence current. For example: For SLG, the positive, negative, and zero-sequence impedance networks are connected in series. For DLL fault- The positive and negative-sequence impedance networks are connected in parallel.

A ground connection is a required condition to create a zero sequence path. No all unbalance current can create zero-sequence. For instance, transformer configurations, such as ungrounded wye-ungrounded wye, grounded wye-ungrounded wye, ungrounded wye-delta, and delta-delta will not allow zero-sequence currents to flow and will have an open path in the zero-sequence network model. (See example below)

 

[HamburgerHelper]

You need too look at how to build sequence networks of a system to understand which components are involved in each type of fault. Sequence networks are used to determine the fault currents of unbalanced faults. The sequence network is created and then can be transferred back to regular phase components. You to get a book called Symmetrical Components by Blackburn. It is the best book that I know that runs through using symmetrical components.

https://powerprotection.fandom.com/wiki/Symmetrical_Components

Simulator of phasors

http://www.powerstandards.com/PQTeachingToyIndex.php

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