1. Faults caused by the influence of ambient temperature on low-voltage electrical appliances
The low-voltage electrical appliances in the optical fiber distribution box are composed of fuses, AC contactors, residual current action protectors, capacitors and meters. The upper limit of the ambient air temperature shall not exceed 40°C; the average value of the ambient air temperature for 24 hours shall not exceed 35°C; the lower limit of the ambient air temperature shall not be lower than -5°C or -25°C.
The optical fiber distribution box transformed by the rural power grid operates outdoors. It is not only exposed to direct sunlight to generate high temperature, but also generates heat itself during operation. Therefore, in the midsummer high temperature season, the temperature inside the box will reach above 60°C. The temperature greatly exceeds the ambient temperature specified for these appliances.
2. Faults caused by product quality
During the transformation of the rural power grid, due to the large number of optical fiber distribution boxes required and the short construction period, the optical fiber distribution box factory needed to supply low-voltage electrical appliances urgently and in large quantities, resulting in the phenomenon that the requirements for product quality were not strict. , causing some products to fail shortly after they were put into operation. For example, some types of AC contactors cannot operate due to the burnout of the contactor closing coil shortly after the optical fiber distribution box is put into operation.
3. Faults caused by improper selection of electrical appliances in the optical fiber distribution box
Due to the inappropriate selection of AC contactor capacity during manufacture, AC contactors of the same capacity are installed for different outlet circuits, and the unbalanced three-phase load is not considered, and the current level of some outlet contactors cannot be adjusted to normal On the basis of the selected model, increase the selection of a current level.
In order to prevent failures in the Fiber Optic Distribution Box, the method of improving the fiber optic distribution box:
1. For an optical fiber distribution box with a distribution transformer capacity of 100kV·A or above, a temperature control relay (JU-3 or JU-4 ultra-small temperature relay should be installed at the side wall of the heat dissipation window in the box) ) and an axial flow fan, which are installed on the box on the left side above the control electrical panel, so that when the temperature in the box reaches a certain value (such as 40°C), the exhaust fan can be automatically activated to forcibly discharge heat to dissipate heat from the box.
2. The protection circuit is used to prevent the failure of the external circuit powered by the optical fiber distribution box. Choose a smaller intelligent phase loss protection.
3. Improve the wiring method of the low-voltage capacitor bank of the original optical fiber distribution box, and change its installation position from the pile head of the AC contactor to be connected between the low-voltage incoming line of the optical fiber distribution box and the meter. To prevent the inaccurate measurement of the metering device due to a phase failure of the capacitor circuit during operation or damage to the capacitor.
4. If a pole-mounted distribution stand is added, when making the shell of the optical fiber distribution box, a 2 mm thick stainless steel plate can be selected, and the size of the optical fiber distribution box will be appropriately enlarged in proportion.
The overall dimensions of the improved optical fiber distribution box are: 1300 mm × 780 mm × 500 mm, in order to increase the electrical safety distance between the outgoing lines of each branch, the outgoing line and the box shell, which is conducive to the operation, maintenance and replacement of agricultural electricians parts, but also to dissipate heat.
As a professional fiber optic distribution box supplier in China, Tuolima has rich experience in high-quality optical fiber distribution box manufacturing. If you want to buy optical fiber distribution box or get more information about optical fiber distribution box, please feel free to contact us!