Questions unit4
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The document contains 5 practice questions related to fault analysis in power systems. Question 1 asks to calculate the fault current and healthy line voltage for a DLG fault at the terminals of a 50MVA generator. Question 2 asks to calculate the line-to-ground fault currents for a fault on a transformer winding with given system reactances. Question 3 asks to calculate the fault current for a SLG fault at a given point in a system shown in a figure. Question 4 asks to determine the fault current, bus voltages, and line currents for a 3-phase fault with a given fault impedance in a system shown in a diagram. Question 5 asks to calculate the fault current for a DLG fault at a given point considering a generator
![Unit IV Practice Questions
Q1. A 50 MVA, 11KV unloaded generator has the following data:
Xg0 = 0.04pu, X1 = 0.3pu, X2= 0.25pu, Xn = 0.1pu, Xf = 0.3pu. Find the fault current and the
voltage of the healthy line if there is a DLG type of fault on the terminals of the generator which is
maintained at 80% of the rated voltage. [2.067KA]
Q2. The given figure shows a power network with two generators connected in parallel to a transformer
feeding a transmission line. The far end of the line is connected to an infinite bus through another
transformer. Star point of each transformer. Generator 1 and infinite bus are solidly grounded. The
positive, negative and zero sequence reactance of various components in per unit on a common
base are :
Positive Negative Zero
Generator 1 0.15 0.15 0.08
Generator 2 0.25 0.25 0.06(neutral
isolated)
Each 0.15 0.15 0.15
Transformer
Infinite Bus 0.15 0.15 0.05
Line 0.20 0.20 0.40
With both generators and infinite bus operating at 1.0 pu voltage on no load, a line-to-ground fault occurs
at one of the terminals of the star-connected winding of the transformer A.
Calculate the currents flowing in the fault.
[-j6.74pu]
Q3. For a power system shown in figure below, find the fault current at point F for a SLG type of fault,
assuming that the pre- fault current in the circuit is zero :
The rating of the components are:
machines(generator as well as motor) : 1200KVA, 600V, X1 = X2 = 10% and X0 = 5%
Transformers : 1200 KVA, 600/3300V and leakage reactance is 5%](https://image.slidesharecdn.com/questionsunit4-130406084039-phpapp01/85/Questions-unit4-1-320.jpg)
![Transmission lines : Reactance is 20% on a base of 1200KVA and 3300V
Q4. Determine the fault current, the bus voltages and the line currents during the fault when a 3φ fault
occurs with a fault impedance of Z f = j0.16 pu. The negative sequence reactance is same as positive
sequence reactance mentioned in the diagram, the zero sequence reactance is 5% and neutral
reactance is 4% for both the machines.
Q5. For the power system shown in the figure, there is a DLG fault at the point F. Calculate the fault
current by taking a base of 100MVA and 11KV in the generator circuit. Rating of generator is
100MVA, 11KV, X1=20%, X2=15% and X0=10%.the voltage at the load point is 60KV prior to the fault.
The neutral reactance of the generator is 5% on its rating.
.
[3.255< 97deg pu]](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
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Questions unit4
- 1. Unit IV Practice Questions Q1. A 50 MVA, 11KV unloaded generator has the following data: Xg0 = 0.04pu, X1 = 0.3pu, X2= 0.25pu, Xn = 0.1pu, Xf = 0.3pu. Find the fault current and the voltage of the healthy line if there is a DLG type of fault on the terminals of the generator which is maintained at 80% of the rated voltage. [2.067KA] Q2. The given figure shows a power network with two generators connected in parallel to a transformer feeding a transmission line. The far end of the line is connected to an infinite bus through another transformer. Star point of each transformer. Generator 1 and infinite bus are solidly grounded. The positive, negative and zero sequence reactance of various components in per unit on a common base are : Positive Negative Zero Generator 1 0.15 0.15 0.08 Generator 2 0.25 0.25 0.06(neutral isolated) Each 0.15 0.15 0.15 Transformer Infinite Bus 0.15 0.15 0.05 Line 0.20 0.20 0.40 With both generators and infinite bus operating at 1.0 pu voltage on no load, a line-to-ground fault occurs at one of the terminals of the star-connected winding of the transformer A. Calculate the currents flowing in the fault. [-j6.74pu] Q3. For a power system shown in figure below, find the fault current at point F for a SLG type of fault, assuming that the pre- fault current in the circuit is zero : The rating of the components are: machines(generator as well as motor) : 1200KVA, 600V, X1 = X2 = 10% and X0 = 5% Transformers : 1200 KVA, 600/3300V and leakage reactance is 5%
- 2. Transmission lines : Reactance is 20% on a base of 1200KVA and 3300V Q4. Determine the fault current, the bus voltages and the line currents during the fault when a 3φ fault occurs with a fault impedance of Z f = j0.16 pu. The negative sequence reactance is same as positive sequence reactance mentioned in the diagram, the zero sequence reactance is 5% and neutral reactance is 4% for both the machines. Q5. For the power system shown in the figure, there is a DLG fault at the point F. Calculate the fault current by taking a base of 100MVA and 11KV in the generator circuit. Rating of generator is 100MVA, 11KV, X1=20%, X2=15% and X0=10%.the voltage at the load point is 60KV prior to the fault. The neutral reactance of the generator is 5% on its rating. . [3.255< 97deg pu]