Publish Time: 2024-06-11 Origin: Site
Fundamental Wave
Definition: According to IEC standards, the fundamental wave is "the first component of the Fourier series of a periodic quantity." In the Chinese power system, it typically refers to a sinusoidal wave with a frequency of 50 Hz.
Harmonics
Definition: Harmonics are "components of the Fourier series of a periodic quantity with orders higher than 1," encompassing integer harmonics, interharmonics, and subharmonics. Practically, harmonics usually refer to integer harmonics with orders higher than 1. Interharmonics are non-integer multiples greater than 1, and subharmonics are multiples less than 1.
Table 1-1 Common Power Waveforms
| Type | Description | Waveform |
Fundamental Wave | A sinusoidal wave with f0 equal to 50 Hz or 60 Hz. | |
Harmonics | fN = N * f0 (where N > 1 is a positive integer), for example: 2nd harmonic, f2 = 2 * f0 = 100 Hz, 3rd harmonic, f3 = 3 * f0 = 150 Hz, 4th harmonic, f4 = 4 * f0 = 200 Hz.… | |
Interharmonics | Frequency is a non-integer multiple of the fundamental frequency greater than 1. fn= n * f0 (n>1 is a non-positive integer) | |
Subharmonic | The second harmonic frequency is a multiple of the fundamental frequency less than 1. fm= m * f0 (m<1) | |
Full Wave | The total power containing fundamental and harmonics is a composite waveform. |
1.2 Harmonics and Power Metering
Harmonic Generation |
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• In an ideal power grid, voltage and current should be sinusoidal at the power frequency. • Nonlinear loads in power systems generate harmonics, significantly impacting the grid when injected. |
The Harm of Harmonics |
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• Minor harmonics can cause metering deviations and data distortions, affecting trade settlements and energy management. • Harmonics increase the risk of grid resonance, causing higher losses, reduced efficiency, and potential overheating, which can lead to fires. They also distort low-voltage equipment supply, impacting performance and lifespan. • Anti-harmonic equipment, including harmonic transformers, is crucial for grid monitoring and requires regular maintenance. |
1.3 Harmonic Transformer
• Harmonic Voltage Transformers: Measure and transform high voltage.
• Harmonic Current Transformers: Measure and transform high current.
• Harmonic transformers are essential for extending the measurement range of electrical instruments and isolating high voltage and large current containing harmonics, converting them into manageable levels for measurement and control.
Table 1-2 Harmonic Voltage Transformer and Harmonic Current Transformer
| Type | Harmonic Voltage Transformer | Harmonic Current Transformer |
Diagram | | |
Purpose | Transform and measure high voltage | Transform and measure high current |
Rated Voltage or Current | 6~110 kV | >6 kV, 0~3 kA or above |
Frequency Range | 50 Hz~3 kHz | 50 Hz~3 kHz |
Class of Standard | Up to class 0.1 | Up to class 0.1 |
Verification Procedures | JJG 1177-2021 | JJG 1176-2021 |
Next article, we will introduce you the TUNKIA solution to harmonic transformer calibration. Stay tuned!
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