Transformer calc

[Gibby106141]

Can anyone help, been given the following question:

• What fault level would be present at the source, feeder 1 and at the load for a system comprising:

Source = 0.050pu.
Transformer = 0.15pu.
Transformer = 0.30pu.
Feeder 1 = 0.50pu.
Feeder 2 = 2.0pu.
Feeder 3 = 7.0pu.

Anyone got any ideas?

 

[breezer]

Anyone got any ideas?

when being taught, if you don't understand ASK!

this is a diy forum, not an information beaureau

 

[Gibby106141]

Breezer, I suppose I deserved that, could anyone point me in the right direction though?

Regards

Mark

 

[ricicle]

Try the Power sector forum on the IET website.I think you have some parameters missing from that question!

 

[Jaymack]

If the transformers were in parallel, unlikely due to the difference in the pu values of impedance, and the feeders are from a common bus after the tfrs: -
Fault Level Source = 0.050pu.
Fault Level Transformer = 0.050 + (0.15 × 0.30)/0.45 = 0.1pu.
Fault Level Feeder 1 = 0.50 + 0.1 + 0.05 = 0.65pu.

Again, I doubt whether the transformers are in series, if you had a SLD, it would be clearer. The p.u. values are calculated similar to resistances in parallel or series.

Jaymack

 

[Gibby106141]

It is also based on a 10MVA base, can someone at least help me with the calculation?