Hi, I have a 22kV source transformer 66/22 Dyn3, and downstream of the 22 I have a 22/11 grounded auto-transformer Yna0. If I have a single phase to ground fault on the 11kV side of the auto-transformer of magnitude (say) 100A, how many earth fault amps will the 22kV relay back at the source...
Hi
What are the advantages and disadvantages of solidly grounding the negative pole of a substation DC system. The DC system would be operating at 48V DC and would be used for protection & control systems. The ground/earth would rise as a result of AC system ground faults and the likes, but...
The problem,
Pole Mounted Transformer (Delta-Star), 22000/415V.
Proposal is to install lightning arresters on 22kV side, mounted to tank.
Tank earthed to pole earth, LV cable also connected to same earth.
If lightning arrester discharges then possibility that HV voltage transferred into LV...
Thanks Kiribanda you've confirmed what i had theorised. We have a relay on the 11 side which covers 11 & 22, i will set the earth fault to a sensitive value of 5 Amps now that i don't have to worry about unbalanced loads on th 22.
Here's the picture. An 11kV 3 phase overhead system is supplied from a 33/11kV Dyn transformer. All along the route of the 11kV line are Dyn connected distribution transformers 11/0.4kV. A few kilometres down the 11kV line is connected an auto transformer with ratio 2:1 to step the 11kV voltage...
All of the distribution transformers (i.e. 22/0.4kV or 11/0.4kV) are either phase to phase or three phase delta connected. So correct me if i'm right or wrong but theoretically with this arrangement there should be no unbalanced condition, i.e. the current magnitudes in each phase may be...
With the solidly grounded neutral of the auto tranny the 11 kV system in effect becomes a 3 phase 4 wire system due to the star points being bonded through ground. Can the ground carry any imbalance current back to the source?
At the zone substation there is a 33/11 Dyn11 supplying the 11 kV bus. About 2 miles away from the sub on one of the sub's 11 kV feeders we're putting in a 2 MVA 11/22 auto stepup.
I have to apply protection to an 11/22 kV step up 3 phase auto transformer. The protection relay is a MiCOM with basic OC & EF elements. The autotransformer is solidly grounded so there is in effect a zero sequence source in front of thew relay. The source side is solidly earthed i.e the 33/11...
Thanks for all your help, it remains a mystery. ScottyUK, if there had been a movement of the winding to earth then our transformer dif prot would have operated and it didn't. 11kV relay operated in 0.45 secs as the fault current was around 2kA (do the maths guys). So the 33kV earth fault trip...
33 kV OC set to 330A (33 kV) with a 0.4 TMS Standard Inverse, 33 kV EF set to 26 A at 1 sec DT.
11 kV OC Set to 210A (11 kV) with a 0.15 TMS Standard Inverse. The 33 kV HV CB on the 33kV side of the Dyn11 transformer is set to 20 A EF and it didn't see a thing, so i'm leaning towards some sort...
A 33kV feeder of ours connects to a remote substation B with a single 33/11kV Dyn11 transformer connected at B, and an 11kV distribution board at B. The relay on the 33kV feede CB at Substation A has Overcurrent & Earth Fault protection. There was a phase to phase fault and the 11kV CB at...
Thanks for all the responses, but here is my predicament, the systems we buy come negative (not positive as i said eariler) earthed, and only have MCB protection on the positive distribution rail, i.e. no negative protection. If i used a floating system then i'd have to fuse the positive and...
What are the advantages & disadvantages of solidly earthing one pole of a 48VDC substation battery? I have a system that i'd like to tie the positive to the substation earth mat, is this a good or bad idea?
