Protecting Transformers From Harmonic Overloading

摘要

For 3-phase wye connected systems, found in most commercial facilities, the presence of multiple phase-neutral connected non-linear loads can lead to serious overloading of transformers, breakers, and wiring. This overloading is the result of harmonic currents drawn by switched-mode power supplies. Systems can be "beefed up" to handle the harmonic currents by doubling neutral wires, over sizing branch circuits and transformers, or utilizing k-rated transformers. Zig-zag transformers or active filters can be added to protect the distribution transformer. A harmonic suppression system, which eliminates harmonic currents in the system by preventing them from ever forming, can unload the entire distribution system without producing waste heat. Whatever harmonic mitigation method is selected, it is clear that the problem of transformer overloading caused by harmonic currents must be addressed before commercial facility power distribution systems can reach the level of dependability demanded by present and future computer based commerce.