Desarrollo de la propuesta Objetivo general y propósito

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the fact that the Mho relay mal-operates whenever faults occur in the presence of FACTS compensation as can be seen in all fault types simulated.

Table 4.1 to 4.4 elucidated the effects of various compensation levels (20%, 40% and 60%) to the fault impedance and location in the power system.

It can be seen from the table that an increase in compensation level further affects fault impedance and consequently the zones coordination of the distance relay.

4.3 A Case of Different Fault types with TCSC (Considering MOV Action)

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Figure 4.37: Mho characteristics of Relay A for 3 phase fault at 50km in the presence TCSC considering MOV protection

Figure 4.38: Mho characteristics of Relay B for 3 phase fault at 50km in the presence TCSC considering MOV protection

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Figure 4.39: Mho characteristics of Relay A for line to ground fault at 50km in the presence TCSC considering MOV protection

Figure 4.40: Mho characteristics of Relay B for line to ground fault at 50km in the presence TCSC considering MOV protection

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Figure 4.41: Mho characteristics of Relay A for line to line fault at 50km in the presence TCSC considering MOV protection

Figure 4.42: Mho characteristics of Relay B for line to line fault at 50km in the presence TCSC considering MOV protection

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Figure 4.43: Mho characteristics of Relay A for three phase fault at 100km in the presence TCSC considering MOV protection

Figure 4.44: Mho characteristics of Relay B for three phase fault at 100km in the presence TCSC considering MOV protection

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Figure 4.45: Mho characteristics of Relay A for line to ground fault at 100km in the presence TCSC considering MOV protection

Figure 4.46: Mho characteristics of Relay B for line to ground fault at 100km in the presence TCSC considering MOV protection

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Figure 4.47: Mho characteristics of Relay A for line to line fault at 100km in the presence TCSC considering MOV protection

Figure 4.48: Mho characteristics of Relay B for line to line fault at 100km in the presence TCSC considering MOV protection

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Figure 4.49: Mho characteristics of Relay A for three phase fault at 250km in the presence TCSC considering MOV protection

Figure 4.50: Mho characteristics of Relay B for three phase fault at 250km in the presence TCSC considering MOV protection

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Figure 4.51: Mho characteristics of Relay A for line to ground fault at 250km in the presence TCSC considering MOV protection

Figure 4.52: Mho characteristics of Relay B for line to ground fault at 250km in the presence TCSC considering MOV protection

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Figure 4.53: Mho characteristics of Relay A for line to line fault at 250km in the presence TCSC considering MOV protection

Figure 4.54: Mho characteristics of Relay B for line to line fault at 250km in the presence TCSC considering MOV protection

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Figure 4.55: MOV characteristics of Phase “a” for three phase fault on the line

Figure 4.56: MOV characteristics of Phase “a” for line to line fault on the line

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The MOV is usually used to protect the FACTS device from very high fault current. Figures 4.37 – 4.54 show examples of the effect of MOV action for different fault locations on a TCSC compensated transmission line. For 40%

compensation on the Ikeja West to Benin transmission line, it is shown that for faults behind the MOV/TCSC, the equivalent MOV/TCSC impedance have small resistive components due to relatively small fault current passing through the TCSC from the source. For faults at 250km (after the MOV/TCSC), the fault current passing the MOV/TCSC becomes more significant. Inaccuracies will be more evident with increase in fault current. Larger fault current has a greater effect on the equivalent impedance as the compensation is reduced and

Figure 4.57: MOV characteristics of Phase “a” for Line to ground fault at 100km on the line

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the MOV partially bypasses the TCSC to protect it from the high fault current.

The compensation level is reduced to nearly zero percent which would have similar effect on the apparent impedance thereby resulting to overreaching or under-reaching of the relay. The effect of distributed parameters was also considered in the system simulations.

In the first case, the fault occurred at the instant of 5.0seconds and was cleared at 5.1667 seconds. For the three phase fault, the result showed that all MOVs (for each of the three phases) have approximately the same conducting currents and absorbed energy. The MOV voltage, current and energy consumption of phase „a‟ for a three phase fault, line to line fault and single line to ground fault are shown in figure 4.55, figure 4.56 and figure 4.57 respectively. Only the MOV on phase „a‟ conducts fault current, while the MOV on phases „b‟ and „c‟ do not conduct fault current for a single line to ground fault

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4.4 Adaptive Relay Setting Results in the presence of TCSC Compensation