Harmonic Analysis Using ETAP Lesson (12) For Power System Engineering Courses

Summary

This tutorial guides viewers through performing harmonic analysis using the ETA program. It covers setting up a project, defining components like power grids, transformers, cables, and static loads, and performing harmonic analysis to detect distortion. Key harmonic sources, such as the static load, are identified, and results show how harmonics affect the system’s total harmonic distortion (THD). The video also explains how impedance varies with frequency and how harmonic sources can be excluded. Finally, it introduces the use of filters to mitigate distortion, with further instruction promised in the next video.

Takeaways

• 😀 **Creating a New Project**: Start by creating a new project in ETAP, name it 'Harmonic One', and use metric units for measurements.
• 😀 **Setting Project Standards**: Choose the NC Code for frequency (50 Hz) and configure other project settings like transformer ratings and impedance values.
• 😀 **Drawing the Power System Diagram**: Begin by selecting a power grid and adding key components such as a two-winding transformer, cables, and static loads.
• 😀 **Configuring Component Parameters**: Define ratings, voltage, and impedance for each component in the system, such as transformers and static loads.
• 😀 **Understanding Cable Configuration**: Select appropriate cables (e.g., 6.6 kV) and specify cable parameters like conductor type, phase configuration, and length.
• 😀 **Load Flow Analysis**: Run the load flow analysis to ensure there are no overloads in the system. Minor under-voltage (e.g., 97%) is acceptable but should be checked for accuracy.
• 😀 **Performing Harmonic Analysis**: Define harmonic sources for each component (e.g., static load) and run harmonic load flow analysis to assess harmonic distortion levels.
• 😀 **Identifying Harmonic Sources**: Static loads are often the primary source of harmonics, and these need to be modeled accurately in ETAP to predict their impact on the system.
• 😀 **Total Harmonic Distortion (THD)**: Monitor critical harmonic limits such as 5% for voltage and 3% for current. Exceeding these limits indicates significant harmonic distortion in the system.
• 😀 **Harmonic Spectrum and Waveforms**: Analyze harmonic spectra to understand the contribution of specific harmonics (e.g., 5th, 7th, 11th) to the total harmonic distortion.
• 😀 **Frequency Scan and Impedance Analysis**: Perform a frequency scan to see how impedance changes with harmonic frequency. Higher frequencies cause higher impedance due to inductive effects.
• 😀 **Mitigating Harmonics with Filters**: If harmonic distortion exceeds acceptable limits, consider using filters to reduce high-order harmonics and improve system performance.

Q & A

What is the primary goal of the harmonic analysis in this lesson?

The primary goal is to conduct a harmonic analysis of a power system using the ETAP software, demonstrating how harmonic distortion can be assessed and managed in a system with various components such as power grids, transformers, and static loads.

Why is the NC code and 50 Hz frequency chosen for the project setup?

The NC code and 50 Hz frequency are chosen because they are standard parameters for power systems, with the 50 Hz frequency being commonly used in many countries for electrical systems, providing a consistent basis for the analysis.

What components are included in the system for the harmonic analysis?

The components include a power grid, transformer (with two windings), cables, and static loads. The static load is assumed to be the source of harmonics in the system.

How is the harmonic source modeled in the ETAP software?

The harmonic source is modeled in ETAP by selecting the appropriate harmonic library model for each component. In this example, the static load is considered the harmonic source, while the transformer is assumed not to produce harmonics unless specified.

What is the significance of the total harmonic distortion (THD) value in this analysis?

The THD value is a key metric used to measure the level of harmonic distortion in the system. It indicates the extent to which the voltage or current waveform deviates from a pure sinusoidal wave. Exceeding the THD threshold can lead to equipment malfunction or inefficiency.

What was the result of the load flow analysis regarding voltage levels?

The load flow analysis showed that the voltage at some buses (e.g., bus 2) was slightly under the required threshold, with an under-voltage of 97%. However, this was considered acceptable for the purposes of the analysis, as values above 95% are generally within tolerance.

How does the frequency scan help in the harmonic analysis?

The frequency scan helps to observe the variation in system impedance as the harmonic frequency increases. It shows how the system's impedance changes with increasing harmonic order, which is important for understanding the system's response to higher-order harmonics.

What causes the impedance to increase with higher-order harmonics?

The impedance increases with higher-order harmonics because the inductive reactance (X) of the system is directly proportional to frequency. As harmonic frequency increases, the reactance rises, which in turn increases the overall impedance.

What is the purpose of excluding harmonic sources in the analysis?

Excluding harmonic sources allows the user to isolate the impact of specific components on the harmonic distortion. By excluding sources like the transformer or grid, the analysis can focus solely on the harmonic effects generated by the static load or other components.

What are the next steps after identifying excessive harmonic distortion in the system?

The next step involves using filters to mitigate harmonic distortion. Filters can be added to reduce the overall total harmonic distortion (THD) and current harmonic distortion (IHD), ensuring the system operates within acceptable limits and preventing damage to equipment.