CYPELEC - Harmonic contents

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CYPELEC

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CYPELEC - Harmonic contents

Harmonic contents

Non-linear loads have a harmonic distortion index that can produce currents in the neutral conductor, in three-phase systems, when the neutral is distributed.

These neutral currents are due to phase currents which have a harmonic content (the most significant being the third harmonic) which is not cancelled out in the neutral conductor.

The value of the neutral current due to the third harmonic may be higher than the value of the phase current. In this case, the neutral current will have a decisive effect on the admissible current of the cables in the circuit.

When entering library receivers, users can define the total harmonic distortion rank 3 (THDI3).

Note:

Some of the devices that can cause significant harmonic currents are, for example, fluorescent lighting banks and DC power supplies, such as those found in computers.

The program evaluates the effect of harmonic currents and applies the reduction factors given in Annex E of IEC 60364-5-52.

It also includes checking the neutral cross-section due to possible harmonic content in three-phase circuits, according to the international standard IEC 60364-5-52, section 524.2.1.