Harmonic Current and LV Surge Protector Relationship

What Is Harmonic Current?

Harmonic currents cause system failures in industrial facilities and especially lead to PCB burnouts. Harmonics fall into the sudden surge category, known as the 8/20 ms waveform. To protect against sudden harmonics, Type 2 or Type 2+3 LV Surge Protection Devices must be used. Surge protection devices do not solve harmonic problems but prevent harmonic-induced equipment damage. Harmonic currents are the general term for currents drawn by harmonic-generating devices from a single-type (50 Hz) power grid at frequencies higher than the grid frequency of 50 Hz. Currents drawn above the 50 Hz frequency are reflected in the system as harmonic currents.

3rd Harmonic 3x50Hz = 150Hz

5th Harmonic 5x50Hz = 250Hz

50th Harmonic 50x50Hz = 2500Hz can be calculated as.

For example, a motor or drive with a nameplate rating of 400 Volt, 50 Hz, 15 kW, Cos Q: 0.7 does not draw current from the grid only at 50 Hz. It also draws high-frequency currents. If it drew current only at 50 Hz, phenomena we call harmonics would not occur. To give an example from daily life: if two people hold hands and start walking together with the same speed and acceleration, they can walk all day without either of them falling. But if the speed and acceleration of one differ from the other, one of them will inevitably fall after a while. This is exactly what devices that draw current at frequencies different from 50 Hz do to the grid. Since the grid is very strong and large, it does everything it can to avoid collapsing. However, one day the grid may not withstand this situation and may be damaged by harmonics. The high-frequency effects that motors and drives impose on the system may eventually be reflected as penalties to businesses by electricity distribution companies.

Harmonic Current and LV Surge Protection Relationship

In the graph above, the waveform of the 1st fundamental component, 2nd harmonic, and 3rd harmonic currents is shown. When examining the waveform, when the voltage should reach a peak value of around 311 volts, it will never reach this value. Because while our voltage is on the positive side, the 2nd and 3rd harmonic components create a negative region, pulling the total voltage value down. Therefore, the effective value will also decrease. Harmonic currents cause serious distortions in the sinusoidal waveform and create serious problems, especially in facilities with uninterrupted production.

Damages Caused by Harmonics;

• Burnouts occur in circuit boards and systems
• As the amount of current drawn increases, it causes heating in conductor cross-sections selected according to the motor’s nominal current value.
• Cause distortions in the grid frequency.
• Cause a decrease in the effective value of the voltage.
• Cause instantaneous voltage drops, leading to equipment failures.
• Cause residual current devices to trip unintentionally.
• Cause changes in the motor’s power factor.
• Reduce the insulation resistance of insulating materials, creating leakage currents and leading to short circuits.
• Prevent compensation systems from operating properly.
• Cause unwanted tripping of fuses and magnetic circuit breakers.

With LV Surge Protection Devices, you have the chance to prevent the sudden damages caused by harmonic currents.

As the most effective solution in this regard, we recommend the Raycap PROTEC C 160/320 Type 2+3 SURGE PROTECTION DEVICE.

If you want to solve the harmonic problem at its root;

*You can use electromagnetic filters

*You can use passive harmonic filters.

For a definitive solution, the use of filters is important; however, they are quite costly solutions. If you want to take quick action on this issue and protect your systems, using Type 2+3 Surge Protection Devices in front of drive panels and machine panels will be beneficial against possible damages.

For detailed information and to request a free site survey, you can contact the YILKOMER support line.

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