Vector jump 1

[Denan]

Hi all,

I hope to get some tips on vector jump, and ROCOF. How to find correct setting for a genset, and what is safe setting.

Situation: On a plant they get trip on vector jump, and the setting is 11deg. I have a settings file showing 6deg for vector jump, and have no idea who changed it to 11 (5-year old plant, I had nothing to do with it until now)

Thanks for any comments!

D.

 

[Runsor]

You requirement for "correct settings" for ROCOF and vector jump is quite tough, because of the nature of these two protection criteria.

Here's a link to a recommendation for ROCOF and vector jump settings for distributed generation by John E Nielsen, ELTRA. Table 2.8.2 on page 32 states the settings.

Note, that these are more coarse settings, than ELTRA used to recommended before an event in the Danish network 1996-02-18. This event is described on page 33. There were a lot of unwanted simultaneous ROCOF trippings all around the distribution network, because of a fault in the transmission newtwork.

http://www.energia.fi/content/root ...ionUri=/fi/julkaisut/sahkovoimatekniikanpooli

 

[Denan]

Thanks Runsor, I will check it out.
I am aware of the difficulty to find correct seting, I was hoping to get a tip where to look for theory on this.
But I found something at SEG.

 

[Denan]

I got a question if I coud suggest another setting, but I don't believe that it would be ok to increase even more (from 11deg), this vector jump happens several times a day.

 

[Runsor]

Here's a link to an IEEE article "A practical method for assessing the effectiveness of vector surge relays for distributed generation applications"

http://www.multi.fi/~saunaaho/Files/VectorSurgeRelayEffectiveness.pdf

But I think - and your case implies the same - that theory won't help, unless you know enough of the affecting parameters of the network including the load behaviour and do analyze the possible fault situations, which may cause a loss of grid situation. In practice combining ROCOF, f<, U< (especially U1<, i.e. positive sequence undervoltage) with the dphi/dt could help.

 

[slavag]

Hi.
I totally agree with Ransor. Ransor are right!!!!!
"Theory won't help", as Ransoe saied,in this case.
Only combination, as ROCOF and f< or U< and f< and df/dt help.
U1<, it's intresting function, but have some problem ( this is a reason, why we don't use it). Not so simple calculation, you must know grid parameters (X, R, etc.). But, as I heart, U1< or PPS ( positive phase seq. )is very popular function in Scandinavien countries.
Voltage shift or dphi/dt, I don't know, many unwanted trips. From other side, I think in German, you must used it.
Best regards.
Slava

 

[Denan]

thanks for replays.
I will see if is possible to get more info about the situation, but it is little bit difficult to find out enough, and probably it is not possible to change relays (upgrade something) because of the extra cost, but i'll see

 

[slavag]

Hi Denan.
See, you have two prblems:
1. several trips of generators per day.
2. extra cost for the other relay.
What is a size of you generator and what is a price of
your non-operated generator?
simple calculation.
new , some very good relay ( I told about generator protection relay with loss of main functionality) with installation and commissioning maybe you can closed with price up to 6000Euro/7500$.
next option, more cheaper, you can bay freq relay 81, that have option f< and df/dt together.
Now, very important points, what is your export power ( average per day) and size of generator. Are power of generator enough for feed your plant, are you have LS functionality? Line from grid to your plant is dedicate line ? Whith AR or w/o?
Regards.
Slava