UML sofeware engineer
Lab Simulation Runs
We run several simulations for this project, which are documented in detail in the remainder of this report.
In the first simulation, we left out both of the transmission pi-section. At the end, we included them in the simulation and observed their influence on the entire circuit.
We also run two different simulation runs to observe power-factor correction. First, we omitted the capacitor at substation 4 and measure the power factor and reactive power. We then repeated the simulation with capacitor connected and compared the measurements.
Report Structure
The report has been separated into several sub-parts, each of which describes a crucial part of the entire circuit. Each section explains the background behind the use of the components and includes important calculation, measurements, and plots.
System OverviewFigure 2 shows the general high-level structure of the project
Generator
The generator is our first sub-system to discuss. This is the source of the entire energy supplied to the rest of the system and is therefore an important part. Figure 3 shows the part of the circuit from Figure 2 which is of interest for the generator.
The major source of energy in the US are the fossil fuels - consisting of natural gas (33%), petroleum (28%), and coal (17%). Combined, they account for 78% of the nation’s energy production. Other energy sources include renewable sources like wind and solar (12%) and nuclear power (10%).
Figure 3: Generator Circuit
A typical generator output voltage is 20-22kV. For our project, we used a value of 22kV. The generator outputs a 3-phase voltage at 60 Hz frequency.
Figure 4 shows the PSCAD plot for the generator voltage (Ea1). We can see the existence of the 3-phases which are 120 degrees out-of-phase to each other.
The peak value can be calculated as follows:
When we compare this with the plot, we can confirm the above calculated peak-value.
Figure 4: Generator Voltage Plot
Step-Up Transformation to High-Voltage
Before energy is transmitted over long distances, voltage levels are up-scaled by many magnitudes in order to keep losses during the transportation low.
Figure 5: Step-Up Transformer
Depending on the distance of the transmission lines, different voltage levels are used. Voltages in the US typically range from 765 kV to 13 kV.
For our project, we used a voltage level of 230 kV. Figure 5 shows the step-up substation from the schematics.
Figure 6 shows the PSCAD plot for the transformer output voltage (Ea2). The peak value can be calculated as follows:
When we compare this with the plot, we can confirm the above calculated peak-value.
Figure 6: Step-Up Transformer Voltage Plot
Transmission Lines
Figure 7: Transmission Towers
Transmission lines come in different lengths and towers. Tower size and shape generally depend on the voltage levels and transmission distance. The size of the towers usually increases with voltage levels and transmission distance. Figure 7 shows a comparison between different transmission towers and pertaining voltage levels.
Step-Down Transformation to Medium-Voltage (Substation 2)
After the transportation over a long distance, voltage levels are reduced for further distribution. In our project, voltage levels are reduced from 230 kV to 69 kV. Energy is usually distributed to multiple major population regions (cities or factories) from here. Each major region has its own substation that steps-down the 230 kV to the required 69 kV.
Figure 8: Step-Down Transformer
After the down-scaling of the voltage, transmission distances are usually shorter than previously.
Figure 8 shows the part of interest from the schematics.
Figure 9 shows the PSCAD plot for the transformer output voltage (Ea4). The peak value can be calculated as follows:
When we compare this with the plot, we can confirm the above calculated peak-value.
Figure 9: Step-Down Transformer Voltage Plot
Step-Down Transformation to Local Distribution (Substations 3 & 4)
Before energy is distributed within cities, voltage levels are again down-scaled. In our project, voltages arriving at the local substations are at 69 kV. The substations then generate 13 kV. This is a standard voltage level for local distribution within cities.
Figure 10: Step-Down Transformers
Large factory buildings mostly have their own substation due to their high energy consumptions. We incorporated this into our project as well.
Figure 10 shows the part of interest from the schematics.
Figure 11 shows the PSCAD plot for the transformer output voltage (Ea6). The peak value can be calculated as follows:
When we compare this with the plot, we can confirm the above calculated peak-value.
Figure 11: Step-Down Transformer Voltage Plot
Load Scenario 1 – Factory with Inductive Load
This load was designed to be an inductive load with a 0.6 PF lagging. We chose this load as large factories usually have a lot of motors which act as inductive loads. Initially, we run the simulation without the capacitor connected. The capacitor was later used to perform a power-factor correction to obtain a power-factor of 1.
Figure 15: Inductive load for factory
Based on the PF, we could calculate the phase angle as follows:
The resistor was chosen to be 100 Ohms. With this information we could calculate the inductive reactance and its equivalent inductance in Henry.
In the PSCAD simulation, we generated plot for the power-factor and the reactive power. The plot for the power-factor can be seen in figure 16. The plot was created using a phase difference element and a cosine element. The reactive power is calculated as follows:
Figure 17: Reactive Power
Figure 16: PF for inductive load
We then repeated the above measurements with a capacitor connected in parallel to the inductive load. The goal was to increase the power-factor to 1, which should result in zero reactive power.
The value of the capacitor was calculated as follows:
Figure 18 and 19 show the results of the power factor correction. We achieved a power-factor of 1 and the reactive power decreased to zero.
Figure 19: Reactive Power with PF-correction
Figure 18: PF for inductive load with PF-correction