You usually want the phases ordered A-B-C from top to bottom or from left to right.
The "symbol" is not an actual symbol, it's just three lines crossing each other.
I attached an alternative to how to draw the circuit...
No SCADA system is designed for transient fault measurement. Either you adapt the solution proposed by ZapSib or you need to find an external TFR. Here's a couple readily on the market:
siemens
abb
-SB
1. You need to ground the neutral on the PT primary side. Without a grounded neutral you will not get a earth fault relay to work trough the PT.
I assume the network is isolated or hiZ earthed.
-SB
The standard zero sequence impedance measurment/test won't detect this since the primary neutral is used as return path.
The only way to test this should be by applying 3-phase voltage on the primary terminals with the primary neutral unconnected and one secondary phase shorted to neutral, the...
Ungrounded wye/grounded wye transformer will definitely provide path for zero sequence flux to flow for line to ground fault on secondary side.The flux path is via the tank of the transformet for core type transformets.Zero seq impedance is typically in the range of 50% to 100%.
No,you don't...
bee79;
I think both 10kA and 20kA are a bit too even and round to be the actual short circuit current. I suppose that these are each panels rated s.c.c.?
You really need to calculate the actual s.c.c. in the lighting panel.
Alajji;
To ensure discrimination of CB on individual circuit , the...
As Bill wrote; It depends.
Total discrimination means that no matter how high short circuit current you have (up to max rated s.c. current of the MCCB/MCB) the downstream device will always trip before the upstream.
There is seldom need for total discrimination; if you know the value of the...
Veritas,
The phasor diagram(s) can be thougth of as a representation of the VT windngs, nothing virtual about that.
Regarding the other issue of phasor voltage being negative; I would say no, it's not negative. IF it were negative the phasor arrow of phase "a" would point towards the neutral...
There, I "cleaned" up my scribbles. Enjoy.
-SBhttp://files.engineering.com/getfile.aspx?folder=a4653fb3-ee7e-40d5-9174-5dbd240146af&file=thread238-405639_r1.pdf
Veritas,
Yes, you're right. Actually that part should indicate the pre-fault conditions. I'll correct that and post a new verion later today. I also need to correct the calculations on page two; I'm missing a "3" in the middle part. It doesn't affect the outcome though.
-SB
