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Introduction to Some Contents of Outdoor Lighting Engineering

Exhibition News 2025-07-03

In LED outdoor lighting projects, a low power factor can cause serious problems and greatly affect the zero line current. In engineering, there has always been ambiguity in the use and control of neutral wires, as well as the use of residual current protectors related to them. This article attempts to provide a clear description and analysis based on engineering cases.

The application of LED lighting fixtures in outdoor landscape lighting has a history of over ten years. Due to the convenience of LED control, the overall scale of such projects has been increasing, with the entire project costing tens of millions or even hundreds of millions of yuan. In this situation, some technical blind spots that were previously overlooked begin to emerge.

Among these technological blind spots, the impact of power factor and zero line current is one of them. Although this issue is simple, it has caused significant engineering problems, hidden dangers, and waste due to its lack of attention.

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In the era of neon lights, ballasts generally have a relatively high power factor, which leads to fewer problems. In the era of LED, the low-voltage switching power supplies used usually do not have PFC [L2] function, resulting in the following consequences:

① In large-scale engineering, due to the low power factor, it may seriously pollute the power grid, and a large number of high-order harmonics will interfere with other equipment.

② Meanwhile, if the power factor is too low, it will also increase the power load of the front-end equipment and increase user investment.

③ Causing excessive zero line current. In old-fashioned circuits, due to the high power factor and low neutral current, commercially available four core cables are also based on this situation, and the diameter of the neutral wire is relatively smaller than that of the phase wire.

④ Severe excessive startup surge current can strongly impact the power grid, causing difficulties in closing the circuit.

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The engineering design unit has already considered and taken some measures regarding the difficulty in closing the ordinary switch mode power supply due to the large input rectification and filtering capacitors, which cause significant impact on the power grid during startup. This is not the focus of this article. Switching power supplies with PFC function, due to their much smaller input capacitance, help reduce startup surge current.

This article mainly describes and analyzes various situations of zero line current in high-power LED projects using three-phase four wire system.