Third Harmonic Current in Neutral

Third Harmonic Current

Infirmness in Neutral Wire with Third Harmonic Current is a serious Electrical Fire Risk. Its degree determines how soon the electrical fire would ignite. Computer, SMPS power supplies, Single Phase UPS and Electronic devices, and LED lighting create triplen harmonic current, also known as third harmonic or zero sequence harmonic; which unlike the normal current and also the industrial harmonic currents, do not get cancelled at neutral but get added and triple at neutral. The high neutral current with associated high frequency triplen harmonic is the perfect recipe that cause infirmness in the neutral system.

A single infirmness at a wrong neutral point could ignite electrical fire at the whole building or at a building section or at an individual equipment. It is thus required to mitigate the triplen harmonics from section by section and floor by floor 3ph supply DB levels. It greatly narrows down electrical fire risk for the entire building.     

Considering actual load currents at floor level DBs for most of Buildings, Shopping malls, IT-companies, Corporate head quarters etc, it is concluded that the following two sizes of triplen harmonic filter would cater for the 80% of clients' requirement, and for the balance 20% higher size filters would be supplied on an individual client's need basis.   

Triplen Harmonic Filter - what rating and where to install?

a)    UPS Output DB: i) Use 5A Filter for up to 10A load current from computer, server and/or PLC/HMI/SCADA and 10A Filter for up to 20A 3ph distribution DB. One filter per DB. ii) For higher currents, please consult us.

b)    LED Lighting/ Elevator DB: i) Use 10A Filter for all types of Elevators and install it at Lift-room DB. ii) Use 5A Filter for LED Lighting DB up to 12.5A load current and 10A Filter for up to 25A load current.