- The frequency of triple
harmonics is in the multiple of 3, i.e. 3
^{rd}harmonic, 9^{th}harmonic and 15^{th}harmonic and so on.

- The triple harmonics are generated by single phase non linear load that have common neutral.
- These non linear loads are common in office, hospitals, commercial buildings, educational building, IT offices. Some of examples are

( 1 ) Compact Fluorescent
Lamp

( 2 ) Electronic ballast

( 3 ) SMPS in the Computer

__Triple Harmonic in Neutral Conductor__- If the load is balanced, the neutral current is zero as the vector sum of all three phase current is zero.
- The current flows through neutral conductor in spite of load are balanced due to presence of triple harmonics.
- All the triple harmonics are zero sequence in nature and they are in phase with all the three phases R, Y and B.
- The neutral current increases up to 2 times phase current due to presence of third harmonics.

__Causes of Triple harmonic__- Burning of neutral conductor due to overloading on it ( or size of the neutral conductor must be kept higher in order to consider effect of third harmonic )
- Cable overheating due to skin effect
- Over heating of distribution transformer
- Higher eddy current losses as the eddy current losses is directly proportional to square of the frequency
- Due to heating, it will reduce the life of transformer, switch gear and other switching devices

__Methods to Reduce / Mitigation Triple harmonic__- The Detuned filter ( Type of passive filter consists of series combination of power capacitor and reactor which offer higher impedance for higher frequency harmonics ) is used to reduce the effect of triple harmonic.
- The tuning frequency of the detuned filter is 133 Hz, which is below third harmonic frequency ( 150 Hz ).
- The amplification
of 3
^{rd}harmonic is reduced by this filter. However this filter does not eliminate the harmonic completely.

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