1. Unreasonable layout of leakage protectorDue to the particularity of the installation site of LED display screen, such as wiring error, line damage, damage of leakage protector in the switch box, failure of some electrical appliances to pass through the switch box, as well as the inevitable misoperation and refusal of leakage protector itself, and the failure to arrange the leakage protector according to the actual power consumption, the total leakage protector tripped frequently.
In this case, in addition to strengthening the management, it is also necessary to reasonably arrange the leakage protector according to the actual situation from the perspective of technology. The leakage protector on the main power supply of the incoming line can be mainly used as the general protection against electrical fire hazards and electrical short circuit, and also as the backup protection for each small leakage protection range. Its rated leakage action current can be selected between 200 500mA, and the rated leakage action time can be selected as 0.2 0.3s. In this way, the impact of surge voltage, surge current and electromagnetic interference on the total leakage protector can be greatly reduced, and the selectivity and reliability of the action of the total leakage protector can be improved. If the secondary leakage protection within each leakage protection range can be in an effective protection state, the frequent tripping probability of the total leakage protector on the construction site can be greatly reduced.
2. There is no effective secondary or tertiary leakage protection within the protection range
The final leakage protector in the switch box is the main protection of electrical equipment. If the final leakage protector is not installed, damaged or improperly selected, it may cause frequent tripping of the superior leakage protector. Because there are many metal conductors and many wire joints in the LED display screen, if the wire insulation is not very good, it will lead to frequent leakage; Some have also added some sockets. In many cases, leakage protectors are not installed, which often causes leakage. Only by forming an effective secondary or tertiary leakage protection mode within each protection range can the frequent tripping of leakage protector be effectively reduced.
3. Leakage protector itself has certain limitations
(1) The current leakage protector, whether electromagnetic or electronic, adopts magnetic induction voltage transformer to pick up the leakage current in the main circuit of electrical equipment. Three-phase or three-phase four wires cannot be arranged in the magnetic ring completely balanced. The three-phase power load of LED display screen can not be completely balanced. Under high current or high overvoltage, a certain electromotive force will be induced in the magnetic ring with high permeability. If the electromotive force is large to a certain extent, it will cause the leakage protector to trip. As the leakage protector with higher rated current adopts a relatively large magnetic ring, the leakage magnetic flux generated is also relatively large, and the leakage current should overcome the magnetization force of the magnetic ring itself, resulting in the higher rated current, lower sensitivity and higher rejection rate of the leakage protector actually used.
(2) The leakage protector has an action uncertain area between the rated leakage action current and the rated leakage non action current. When the leakage current of the leakage protector fluctuates in this area, the leakage protector may trip irregularly.4. Unreasonable selection of leakage protector(1) The rated leakage action current used in the switch box exceeds 30mA, or the leakage protector exceeds more than twice the rated current of electrical equipment, or the leakage protector with time delay is selected. Due to the improvement of rated leakage action current or the decrease of protection sensitivity, the last level leakage protector does not act in case of leakage fault, The superior leakage protector may act.
(2) When the LED display is powered on, the starting current is often large, which may trip the leakage protector. Therefore, power on the box of the display screen in batches as much as possible. In addition, electromagnetic leakage protector which is not sensitive to surge overvoltage and overcurrent shall be selected generally; Or select an electronic leakage protector 1.5 2 times larger than the rated current, but as the final leakage protection, the rated leakage action current shall not be greater than 30mA.
Bao’an District Shenzhen City, China
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