How would you describe a fault like that ?

[usercan]

Recently, I got fault records from a relay to analyze it. But I don't understand the phasor diagram of the fault. The angle between Ib and Ic is 178. The angle between Vb and Vc is 118. Now is this a L-L or L-L-G fault ? I'm also putting the picture here.

 

[Palletjack]

What kind of fault?
I don’t see the expected voltage collapse if it were a BC fault, which is about what it looks like.
Also, the expected 0 reference isn’t noted.

 

[davidbeach]

How about providing the osscilography, or better yet the event file? There's so much that a single phasor plot doesn't show.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[RRaghunath]

Currents IA & IC are in phase and adding up to be equal and in phase opposition to IB.
But there seems to be no impact on voltage vectors absolutely, in terms of magnitude as well as phase angle??
If you can share comtrade file, we can try to analyse better I suppose. Trip / Event records also help.

 

[usercan]

Hello, sorry for late reply. I'm sharing the oscillographic records here. This is a cable + OHL line. The line is three terminal line but protected from only two terminals with cable differential relay. Because there is no generation on the third terminal. So the current flows to the third terminal is not known by the relays on other terminals. The differential current threshold is set 600 A so the relays will not operate during load conditions. (400 kV line , 125+125 MVA installed power on the third terminal ) In fact, this was a relay misoperation due to improper setting because only the load conditions was considered on the third terminal but fault conditions should've been considered too. On the other hand, I thought there was a fault on the low voltage side of the third terminal substation and it was seen as a differential current by relays on other terminals. But when I ask them if there was any fault in the low voltage side of the third terminal substation, they told me there wasn't. And I don't get it how this happened. There is an electric arc furnace on the third terminal substation. Is there any possibility that the load side caused some kind of transient overcurrent with a vector diagram like that?

 

[davidbeach]

What is a “rar” file? COMTRADE format might make it easier for others to look at the event. Also, shouldn’t there be two events if it was an 87L trip?

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[thermionic1]

Rar is a file compression format, similar to Zip. 7 Zip supports it. Synchrowave doesn't show any analogs available for a phasor diagram.

 

[jghrist]

Possibly a phase-ground fault on the low side of the third terminal substation (with B & C current on high side of delta-wye transformer), turning into a 3-phase fault. Phase A seems to be load current. Fault could have been temporary and cleared after the 400 kV tripped. What is KARSI_DIF_SLK that asserted at about 920 ms. After that, it seems like a low level 3-phase fault.