The standard grounding method of LED display?

　　1. It is considered that the lower end of the column of the outdoor column structure is connected with the ground, so the display screen does not need to be grounded;

　　2. It is considered that the power supply is locked on the box, and the boxes are connected with each other by the lock catch, so the structure grounding means that the power supply is also grounded.

　　There is a mistake in these two methods. Our columns are connected with the foundation bolts, which are embedded in the concrete. The resistance of the concrete is 100-500 Ω. If the grounding resistance is too high, the leakage current will not be discharged in time or there will be residue. The surface of our box is sprayed with paint, and the paint is a poor conductor of electricity, which will lead to poor contact of box connection grounding or increase of grounding resistance, and it is possible that electric sparks may interfere with the screen signal. As time goes by, oxidation and rust will appear on the box or structure surface, and the fixing parts such as screws will gradually loosen with the thermal expansion and cold contraction caused by the temperature difference change. The effect of structural grounding will be weakened or even completely invalid. Potential safety hazard is formed. This may lead to leakage current, electric shock, chip damage due to interference and other safety accidents.

　　So, what should the standard grounding be? As shown in the figure below, the power input terminal has three terminal blocks, which are the live line terminal, the neutral line terminal and the grounding terminal. The correct grounding method is to use the yellow green two-color wire dedicated for grounding to connect all power ground wire terminals in series and lock them, and then lead them out and connect them to the grounding terminal.

　　If there is no grounding terminal on the site, it can be connected to the iron water pipe or iron sewer pipe and other buried pipes that are in good contact with the ground. To ensure good contact, the terminal should be welded on such natural grounding body, and then the ground wire should be locked on the terminal, and binding connection is not allowed. However, flammable and explosive pipelines such as gas shall not be used. Or the grounding body shall be buried on site. The grounding body can be angle steel or steel pipe, which is buried horizontally or vertically in the ground as a simple grounding point. The grounding point should be selected in a remote place to avoid pedestrians or vehicles damaging the grounding body.

　　When we are grounded, the grounding resistance must be less than 4 ohms to ensure that the leakage current is released in time. It should be noted that the ground potential will rise in a short time due to the diffusion of ground current when the lightning protection grounding terminal discharges the lightning current. If the LED display screen is connected to the lightning protection grounding terminal, the ground potential will be higher than the display screen, and the lightning current will be transmitted to the screen along this ground wire, causing equipment damage. Therefore, the protective grounding of LED display screen shall not be connected to the lightning protection grounding terminal, which must be more than 20 meters away from the lightning protection grounding terminal. Prevent the counterattack of ground potential.

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