Question 7.8: For the system of Example 7.5, find the short-circuit curren...

Electrical Energy Systems

For the system of Example 7.5, find the short-circuit currents at the fault point for a balanced three-phase fault through three impedances each having a value of $Z_{f}= j0.05 p.u.$

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Question: 7.6

For the system of Example 7.5 find the voltages and currents at the fault point for a double line-to-ground fault. Assume Zf=j0.05 p.u. Zg=j0.033 p.u. ...

Verified Answer:

The sequence network connection is as shown in Fig...

Question: 7.7

For the system of Example 7.5, find the voltages and currents at the fault point for a line-to-line fault through an impedance Zf = j0.05 p.u. ...

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The sequence network connection is as shown in Fig...

Question: 7.10

Consider the 11-kV radial system shown in Figure 7.42. Assume that all loads have the same power factor. Determine relay settings to protect the system assuming relay type CO-7 (with characteristics shown in Figure 7.43) is used. ...

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Question: 7.4

Obtain the sequence networks for the system shown in Figure 7.17. Assume the following data in p.u. on the same base. Generator G1: X+ =0.2P.u. X- =0.12 P.u. X0 = 0.06 P.u. Generator G2: X+ = 0.33 P.u. X- = 0.22 P.u. X0 =0.066 P.u. Transformer T1: X+ = X- = X0 = 0.2 p.u. Transformer T2: X+ =X- = X0 ...

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Question: 7.9

Consider a Δ/Y-connected, 20-MVA, 33/11-kV transformer with differential protection applied, for the current transformer ratios shown in Figure 7.37. Calculate the relay currents on full load. Find the minimum relay current setting to allow 125 percent overload. ...

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I_{P} ...

Question: 7.5

Consider a system with sequence impedances given by Z+ = j0.2577, Z- = j0.2085, and Z0 = j0.14; find the voltages and currents at the fault point for a single line-to-ground fault. ...

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The sequence networks are connected in series for ...

Question: 7.2

Given that V0=100 V+=200∠ 60° V-=100∠ 120° find the phase voltage VA, VB, and VC. ...

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V_{A}=V_{+}+V_{-}+V_{0}

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Question: 7.1

The following currents were recorded under fault conditions in a three-phase system:IA=150∠45° A IB=250∠150° A IC=100∠300° A Calculate the values of the positive, negative, and zero phase sequence components for each line. ...

Verified Answer:

I_{0} =\frac{1}{3} \left(I_{A}+I_{B}+I_{C}\...

Question: 7.3

Draw the zero sequence network for the system shown in Figure 7.15. ...

Verified Answer:

The zero sequence network is shown in Figure 7.16.