Questions practice unit iv
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Power System Analysis, Symmetrical fault,
![Unit IV Practice Questions
Q1. A symmetrical short circuit occurs on the 22KV load bus bar. Find the fault apparent power and the
fault current. Choose a base of 150MVA. Also draw the reactance diagram
[1.91KA, 73MVA]
Q2. A 50 MVA, 11KV, 3 phase alternator was subjected to different types of faults. The fault currents
were: 3 phase fault 1870A,LL fault 2590A and SLG fault 4130A. The alternator is solidly grounded. Find
the per unit values of the 3 phase sequence reactances. [1.403, 0.351, 0.151]
Q3. A generator connected through a 5 cycle circuit breaker to a transformer, is rated 100MVA, 18KV
with 19%, 26% and 130% as sub- transient, transient and steady state reactances respectively. It is
operating under no load and rated voltage when a three phase short circuit occurs between the breaker
and transformer. Find:
(i) The sustained short circuit current [2467]
(ii) The initial rms current in the breaker [16882]
(iii) The maximum possible DC component of the short circuit current in the breaker
Q4.
A 3 phase fault occurs at
point F. The reactances
are marked in per unit
values based on 100MVA.
Neglecting the pre fault
power and losses,
calculate the fault MVA at
F. Allow a multiplying
factor of 1.4.
[1430, 2000]](https://image.slidesharecdn.com/questionspracticeunitiv-130507003022-phpapp02/85/Questions-practice-unit-iv-1-320.jpg)
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Questions practice unit iv
- 1. Unit IV Practice Questions Q1. A symmetrical short circuit occurs on the 22KV load bus bar. Find the fault apparent power and the fault current. Choose a base of 150MVA. Also draw the reactance diagram [1.91KA, 73MVA] Q2. A 50 MVA, 11KV, 3 phase alternator was subjected to different types of faults. The fault currents were: 3 phase fault 1870A,LL fault 2590A and SLG fault 4130A. The alternator is solidly grounded. Find the per unit values of the 3 phase sequence reactances. [1.403, 0.351, 0.151] Q3. A generator connected through a 5 cycle circuit breaker to a transformer, is rated 100MVA, 18KV with 19%, 26% and 130% as sub- transient, transient and steady state reactances respectively. It is operating under no load and rated voltage when a three phase short circuit occurs between the breaker and transformer. Find: (i) The sustained short circuit current [2467] (ii) The initial rms current in the breaker [16882] (iii) The maximum possible DC component of the short circuit current in the breaker Q4. A 3 phase fault occurs at point F. The reactances are marked in per unit values based on 100MVA. Neglecting the pre fault power and losses, calculate the fault MVA at F. Allow a multiplying factor of 1.4. [1430, 2000]