Hi Pete,
is there any automatic transfer system in your load center? (I mean a system which automatically open the incoming on undervoltage and consequently, checking adequate interlocks, close the tie).
If not, to lose coordination between HV and LV side of the transformer can be, in my...
I fully agree with rasevskii.
Ciao
Erminio
The difference between overload and short circuit lies in the nature of the fault, not in the value of the current.
Hi Pete,
I think it is problem to loose coordination between incomer or tie and motor feeder, as the portion of the load center feeds more than one user (motor).
I consider the neighborhood of 5750 A a possible fault value, so I would increase current setting of both the incomer and the tie...
Hi Pete,
I think that, in your "Devil's advocate" position, you mixed two subjects....
1)
For phase faults it means to consider the minimum fault current: ph-ph fault = 0,866*I3phmin (I3phmin calculated with minimum source short circuit power).
For ground faults, if neutral point is solidly...
Hi Living2learn,
in my opinion, as a first approach you'd better consider the sum of the 3 inrush currents.
The reality will be probably slightly different:
- the inrush current value you've indicated is the maximum one and it depends by the instantaneous voltage at the CB closing instant;
-...
Hi,
you should check IEC 364-4 ("Electrical installations of buildings part 4: protection for safety")for safety requirements of houses electrical circuits.
Ciao
Erminio
The difference between overload and short circuit lies in the nature of the fault, not in the value of the current.
Hi,
as Slavag is saying:
- protection systems for grounded star point networks can be based on zero sequence current measurements
- in case of ungrounded star point networks, protection systems will be probably based on zero sequence voltage measurements (it depends by the lines type and length)...
Hi Denan,
the public utility, which the plant is connected to, should have requested to install some protection functions on the grid breaker which are needed both to protect the plant from grid faults and to protect the grid from plant internal faults.
Both actions are done by means of opening...
Hi isquredr,
it is a typical connection for OLTC controller.
More explanations can be found for example at
http://www.reinhausen.com/en/XparoDownload.ashx?raid=16747
(Maschinenfabrik Reinhausen Tapcon 240 Manual page 144).
Ciao
Erminio
The difference between overload and short circuit lies...
Hi Odlanor,
the answer is in the last page of the document (as I googled it):
By using this method it is possible to test the differential protection for an n-winding
transformer by testing in between two windings at a time. However, note that the SrMax
value shall ALWAYS be used for the base...
Hi Denan,
unfortunately I'm not able to get any suggestion by the SCADA logs...
As nothing was found in protection's alarm log, I'll start to consider the possibility of a fault which has occurred after generator CB was open while the machine was de-excited (but with residual flux) and starting...
David, Zogzog
thanks for your explanations.
I asked to delete my post as jps1 was asking for reference to standard and I wasn't able to give precise ones.
I want to check about it in IEC standards, but unfortunately I haven't get it yet.
Thanks
Ciao
Erminio
The difference between overload and...
Hi Denan,
I'm still putting ideas on the table...
According to sld generator CT's are 150 A primary: machine rated current should be less.
The currents measured from 14:58:52,250 is 250 A (peak) = 175 A (rms): overcurrent protection trip is becoming a more real hypothesis.... But I agree with...
...An overcurrent trip???? It could be compatible with the time delay (about 2 s) and it could be caused by malfunction (or absence) of load shedding function in the plant...
We are back to previous questions: which is the generator rated current? And which are the primary values of the traces...
My first impression is that the generator have fed an external 3ph fault (duration around 70 ms).
Then I suppose they've got a disconnection of the grid and the plant started to run in island condition: your generator seem to start to regulate voltage and frequency in the network, if I'm not...
