Mr. Phil Corso Sir,

We started first time one used turbine alternator of M/S AEG Type S 7085 d4 6.3KV 20MVA. The phase rotation mentioned on name plate are VUW<-. The alternator rotation is anti clock looking from none drive end. There were six terminals with no marking coming out from alternator. I assumed reading from left to right in front of terminals these are U V W and X Y Z. Because of physical obstruction I made Star and ground to UVW and brought XYZ assumed L1 L2 L3 of 6.3KV brought out for supply.

I have had to synchronize these with a 20MVA transformer 6.3V/11KV. In synch check relay both generator and bus PT connected together in order of left to right Gen L1, L2, L3 and bus L1, L2, L3.

The unit synchronized with utility and running satisfactory but the protection relay is displaying Negative sequence voltage 100% and positive sequence voltage 0%. similarly -ve seq current 26% and +seq current 0%. Kindly suggest me where is I am doing something wrong? and how can I rectify it.

I shall be obliged.
Best Regards
Shaheed

 

Mr. Phil Corso
Sir,

I am doing some correction in my above post.

We started first time one used turbine alternator of M/S AEG Type S 7085 d4 6.3KV 20MVA. The phase rotation mentioned on name plate are VUW<-. The alternator rotation is anti clock looking from none drive end. There were six terminals with no marking coming out from alternator. I reading from left to right in front of terminals I assumed that these are W V U and Z Y X. Because of physical obstruction in front of bus bars, I made Star and ground to WVU through NGR and brought out ZYX I assumed them as L3,L2,L1 of 6.3KV.

I have had to synchronized unit with a 20MVA step up transformer 6.3V/11KV. In synch check/ protection relay "Deif" both generator and bus PT connected in order of left to right Gen L1,L2,L3 and bus L1, L2, L3. Please point it that I am considering L1 phase of generator that is placing to my right hand and in Dief synch relay connection L1 PT wire placing to my left hand.

The unit synchronized with utility and running satisfactory but the protection relay deif is displaying Negative sequence voltage 100% and positive sequence voltage 0%. similarly -ve seq current 26% and +seq current 0%. I am doing something wrong? .I think to inter change L1 and L3 the PT wires of gen and bus in Dief protect/ synch rely.

Kindly suggest me.
I shall be obliged.

Best Regards
Shaheed.

 

Shaheed…

reur observation that Neg-Seq relay displayed 100%... with generator under some load, or with zero-load?

Phil Corso

 

Shaheed... can you provide additional detail?

1) Neg-Seq relays are typically connected only to CTs; PTs are not required! Is the Relay Hardwire-based or Microprocessor-based?

2) My earlier question was to determine if it operated without current? If so, and it’s hardware-based, then the Relay is suspect!

3) Is the Relay connected to its own set of CTs, or is it in series with others? If the latter, then its position in the loop is critical!

4) Have you tested it with a Protective-RelayTest Set, i.e., single-phase current injection?

5) If none of the above is pertinent, then I suggest you keep the middle-phase connection, and interchange the outer two!

Regards,
Phil

 

Dear sir,

1- It is Deif company made generator paralleling controller I think microprocessor based. The unit required CTs and PT connections I think without PT connection negative sequence U voltage measurement would not possible.\
2- The relay tripping is disabled but is indicating negative seq U at load. At no load not yet tested.

3- The relay connections are to its own CT and PTs.

4- Not tested through injection test.

5- Thank you for suggestion at the present unit is running at full load I shall inter change L1 & L3 PT wire of both side gen & bus at any down time of the unit.

Best Regards,
Shaheed

 

Shaheed... start with CT exchange first.

Reur your observation that the '46' relay displayed 100% negative and 0% positive. At the time, was the generator deiveringpower?

Phil

 

Sir,

Thank you its your very good point that if I go to inter change the L1 &L3 PT then CTs of L1 & L3 should me first inter change.

You are right sir my observation is that relay 46 is displaying 100% negative U (Volts) and 26% negative I (Current) while 0% positive U & I.

Regards,
Shaheed.

 

Shaheed...

repeating... was the Generator connected to and providing power to 3-phase load at the time the '46' was displaying both pos @ neg-sequence values?

Phil

 

Shaheed...

if you are able to synchronize, then both the power connections and PT connections are OK. The problem is with the Neg-Seq Relay's CT secondary connections.

I’m unfamiliar with how DIEF couples line voltages to the Neg-Seq current function! I strongly urge you to contact DEIF for advice!

Phil

 

Sir,

The unit is running synchronized at 13MW load. The rely 46 is a built in relay in DEIF controller. You are estimating that if unit is synchronized then PT connection are OK no need to change,YES. PT connections are ok in such a way that I have brought anti clock phase sequence PT connection to DEIF (synch/ protect controller) from 11/6.3KV transformer that is my bus bar supply and matched it in same anti clock phase sequence with 6.3KV generator. Now at 6.3KV voltage level sequences of generator and bus bar is anti clock phase rotation, it is reflecting in relay 46 as negative phase sequence 100% but on the other hand the system is running well synchronize because at step up side of the Transformer where voltage level is 11KV the phase sequence of rotation I kept clockwise (positive phase sequence) that is same as of utility or other generators running parallel on same bus of 11KV.

I appreciate your recommendations I shall also get advise from DEIF.

Regards,
Shaheed