FIGURE 3 shows part of an electrical supply system. Draw the impedance diagrams reducing to a single impedance. Calculate the fault MVA levels in each unit for a fault on the left 3.3 kV bus with the bussection switch B open and A closed. Use a base MVA of 10 and show the fault MVA levels on a diagram. Comment on the result and suggest a method of improving the system to limit the fault MVA through T1 to approximately 5 × FL current. (It is not necessary to recalculate.)
Is 30 ok? i do not require a great level of detail, yes the fault is indicated to be on 3.3 kv busbar so by sqrt 3. I have calculated x pu for transfomers and generators, i just lose it when considering what is parrallel and series because of the switch being closed.
Here are answers in the following link. G3 rating is assumed as 16MW. Enlarge figures for reading.word file
The fault MVA through T1 IS 116.67MVA. To reduce it to 5* full load current, we will have to introduce impedance in series with T1.
kindly rate the answers.
Sorry G3 is 1.6 MW
Yes this is fine , it is greatly appreciated .