Using the symmetrical values I am trying to evalute the following circuit only f
ID: 2083318 • Letter: U
Question
Using the symmetrical values I am trying to evalute the following circuit only for fault 1.
The circuit that follows was simulated.
The simulation returned the following measured results:
To analyze the circuit with the symmetrical values, the following equivalent circuit was used:
Using this method I am getting values that look similar to an A-ground fault while the measured values appear to be a B-ground fault. What could be causing this descrepancy?
Fig. 1 Equivalent System B1 uiv. Source 500 kV, 60 Hz 2 j30 Q. Internal equivalent voltage source re-fault power flow E 31.002 12.5 p.u. 500 kV transmission lines 50 mi 100 mi F1 Relay under study is the one associated with this CB 500-kV Line Parameters 0.073 j0.8 2/ mi L1 L2 0.1+ j2.6 2/mi C 0.013 A /mi B3 Equiv. Source 500 kV, 60 Hz Internal equivalent voltage source E -0.994Lo p.ru.Explanation / Answer
Going through the snapshots you have attached, i have the following observations
1. The equivalent circuit which you have drawn with all the sequence components contains Es2, Er2, Es0 and Er0. I dont know what values youbhave taken for them but they are suppose to be zero as negative and zero sequence components don't have a voltage source in their equivalent circuits. Only positive sequence components have voltage source in their equivalent circuits.
3. In the equivalent circuit which you have shown, for F1 the full line impedance of Zl1 will come into the picture and d part of impedance of Zl2 will come into picture. So Zl1 will come fully in all the three networks and mZl2 will come on the left side of the fault and (1-m)Zl2 will come on the right side of the fault. You have not shown Zl2 in your any of your networks which would lead to an error. Include the positive, negative and zero sequence component of Zl2 as i mentioned above and consider full impedance value of Zl1 and recalculate.
3. The fact that you are getting values which appear to be B-ground fault as per measured value in simulation and a A-ground fault as per your method can be due to a mistake while doing simulation. Instead of a A-ground fault you might have selected a B phase-ground fault in the software so causing a discrepancy in the results obtained.
Other than these three mistakes there seems to be no other reason as to the values will differ.
Kindly check these three observations and see for any changes you might get.
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