FINAL DATA SHEET Experiment No. 2 – Medium Length Line Nominal T Method Name: Carvey Ehren R. Maigue DIAGRAMS & CIRCUITS USED Experiment No. 2 – Medium Length Line Nominal T Method Fig 1.0 Fig 1.1 Fig 1.2 Fig 1.3 Fig 1.4 Fig 1.5 Fig 1.6 GRAPHS, CHARTS & CURVES Experiment No. 1 – Short Line Investigation Fig 2.0 Fig 2.1 Fig 2.2 Fig 2.3 Fig 2.4 Fig 2.5 Fig 2.6 Fig 2.7 Fig 2.8 Fig 2.9 Fig 2.10 DISCUSSION Experiment No. 2 – Medium Length Line Nominal T Method Software and Circuit For this experiment, Tina Version 9.3.50.47 SF-DS has been used. The students were tasked to determine the characteristics of a medium length line with a nominal T configuration represented by figures 1.0 and 1.1. The circuit shown in figure 1.2 was made using the software to simulate the circuit configuration. It can be observed that unlike the previous short line model, the medium line nominal t model now has resistive and inductive components in both ends with a shunt capacitor in between, parallel to the load and supply. No load conditions It can be observed that under no load conditions, as shown in figures 1.3 and 1.4, current still flows in the circuit with the shunt capacitance as a load. It can also be observed that among the two line drops only the sending end line impedance carries a voltage drop labeled as “Vdrop1” in this experiment. This is true since the receiving end line impedance is considered floating without a load. It can also be observed from the aforementioned figures and figures 2.0 and 2.1 that a higher shunt capacitance value increases voltage drops and current, thereby increasing shunt capacitance loss. This consideration is very important since it would mean that on such systems, even under no load condition, power is still being lost and consumed by the transmission system. Full load condition Under full load condition both cases showed immense changes in the phasor diagrams shown in figure 2.2 and figure 2.3. Several phasor components emerged such as voltage drop on receiving end line impedance, voltage and current in the receiving end, and power consumed in the receiving end as well. Comparing the two configurations, it can be observed that a higher shunt capacitance causes the phasor angle of the sending end to swing from a lagging position to a leading position. This would change as R load is lowered, and as shown in figure 2.4, the sending end voltage became lagging and almost had the same phasor configuration. This can be attributed to the load R being small that the system shifts to a more reactive type of system. It is also important to take note of the phasor angle and power factor of the receiving end, in both runs and under all R load values, the PF remained to be 1 or in unity. The main reason is the nature of the load, being purely resistive, the voltage and current’s phasor angles would remain in phase. Voltages The experiment requires the students to sweep the resistive load values within the range of 10 Ohms to 50 Ohms, while observing the changes in parameters. As seen in figures 2.5 and 2.6, the sending end voltage remained the same, however as R load increases, the shunt voltage drop and the load voltage increases. Conversely, as the R load increases, the V drop across the line impedances decreases. Comparing the results of run 1 and run 2 it can be observed that a higher shunt capacitance tends to increase component voltage values by a small amount as seen in figures 1.5 and 1.6. Current The resulting currents after varying the loads across multiple values can be seen in figure 2.7 and 2.8. Several observations can be drawn from the figure. First, as R load increases, the sending and receiving end currents decrease. This holds true to Ohm’s law. However, it can also be seen that as R load increases the shunt capacitance current also increases. Further, it can be observed that a higher shunt capacitance value increases the magnitude as well. A peculiar observation can be seen in comparing the sending current and the receiving current magnitudes. The receiving end magnitude tends to be higher. However, if phasor angles would be considered, it can be seen that the receiving end current and the shunt capacitance current when added would yield a value the same to the sending end current. This is true and follows KCL. Power and Phasors The power values for both cases can be seen in figure 2.9. It can be seen that as R increases P in general decreases; however an inflection point can be seen between 10, 15 and 20 and can be attributed to maximum power transfer parameter. It can also be observed that a higher shunt capacitance value increases the overall power profile of the system. Efficiencies and Voltage Regulation It can be observed from figure 2.10 that as R load increases, the efficiency increases as well. Conversely it can be observed that as R load increases the voltage regulation value for both configurations drastically decreases. Although minutely, it can still be observed that a higher shunt capacitance value tends to lower overall voltage regulation values and increase overall efficiency values. CONCLUSION Experiment No. 2 – Medium Length Line Nominal T Method From the observations, analysis of results and discussion, the following can be drawn: Medium line systems also consider capacitance and admittance aside from resistance and inductance of the system. Under no load conditions the sending and receiving voltage are different, this can be attributed to the shunt capacitance that acts as a load even during no load conditions. For medium line transmission systems with a nominal T model, the sending end current is the summation of the shunt capacitance current and the load current in alignment to Kirchhoff’s Current Law. A purely resistive load would yield unity power factor regardless of the line conditions. The system becomes more efficient as resistance of the load increases. Higher shunt capacitance values also improve the efficiency and voltage regulation characteristics of the system. Any reactive component will cause the system to have an inflection point in terms of its power and load curve. This might be related to maximum power transfer but further investigation must be done to be conclusive. Overall, the experiment has been successful. It allowed the students to determine medium line characteristics, construct a nominal T circuit using TINA as a simulation software, determine the voltage regulation and efficiencies of a nominal T configuration, and construct the relevant phasors needed. QUESTION AND ANSWERS Experiment No. 2 – Medium Length Line Nominal T Method 1. What did you observe about the value of the receiving end and sending end currents in the nominal T circuit as compared to the currents in a short line circuit? Explain your answer. Ans. As opposed to a short line circuit, the nominal T configuration has unequal receiving and sending current. This can be attributed to the shunt capacitance which also functions as a load. By KCL, a portion of the sending end current flows through the shunt capacitance branch causing the receiving end current to be unequal to the sending end current. 2. Why is the capacitance of the line being considered in the analysis of medium length lines? Ans. As the line lengthens the shunt capacitance value causes the admittance value to increase which causes current to flow which in turn results to a voltage drop. This causes a power loss. It is important to consider since the power loss can still occur even at a no-load condition due to its configuration of being in parallel with the load and supply. 3. What causes the voltage at the receiving end to rise more than the voltage at the sending end at low load conditions? Ans. In this experiment, such has not been observed. However, such happened to current. It can be attributed to the system becoming more reactive with a leading power factor. The real component increases but the over all complex power of the system remains conserved by compensating with the reactive component of the parameters through changes in their phasor angle.
