Low-voltage switch belongs to the high-frequency electrical appliances in low-voltage electrical appliances. They are often not used alone, but installed in distribution cabinets and distribution boxes, and used in conjunction with other electrical components in the circuit. So in the process of using, it is inevitable that malfunction will occur.
I. Short Circuit in Switchboard of Distribution Box
1. Supporting splints (porcelain or bakelite) and insulating base of inserting contacts in distribution cabinet are dirty, damp or mechanically damaged.
Solutions: Regular cleaning and inspection should be strengthened, damp bakelite plywood and base should be dried, damaged equipment should be replaced in time, and attention should be paid to reducing the spacing of mother row support plywood in order to improve its dynamic stability.
2. Improper selection of electrical components in distribution cabinet (insufficient sectional capacity).
Solution: Electrical appliances with appropriate interruption capacity should be selected according to the load size, and reasonable protection circuit should be designed.
Procedure: Operating rules should be strictly enforced to prevent misoperation, simple insulation cover should be installed, or insertion insulation baffles should be installed between adjacent switch boards.
4. After power outage and maintenance of distribution cabinet, due to negligence, wrenches, spindles and other tools are forgotten on the bus. Before power transmission, they are not carefully checked and short circuit occurs after power transmission.
Solution: It should be operated in strict accordance with the relevant electrical maintenance regulations. After the completion of the maintenance, light tools should be used to prevent forgetting.
5. Short circuit of switch board is caused by small animals such as rats and snakes drilling into distribution cabinet.
Solution: Protective net can be installed to prevent small animals from penetrating.
II. Overheating of bus connection in distribution box
1. Poor contact of monorail busbar joints
Solutions: Load should be transferred immediately, after power failure, the contact area should be dismantled and treated or replaced with a new bus. For a circuit that does not allow power failure or load transfer for a time, forced cooling of the contact area can be temporarily carried out by a fan, but maintenance must be arranged as soon as possible. Conductive paste should be applied to prevent electrochemical corrosion at the contact area and reduce the joint. Contact resistance has a good effect. Therefore, DJG-I and II conductive pastes should be applied at the contact point of the mother row whether it is disassembled or replaced. The non-contact part of the new replacement bus should be painted. Painting can improve the comprehensive heat dissipation and wash, and reduce the body temperature rise. For the same mother row, the temperature rise of the painted mother row is about 74% of that of the unpainted mother row.
2. Too tightly or too loosely screwed butt bolts of the main row of the distribution box
Solution: The bolt is screwed too tightly, the washer part of the mother row is compressed, the cross section is reduced, and the current passes through, causing heat. At the same time, due to the expansion of aluminium and copper wash larger, the washer part of the mother row will be further compressed. When the current decreases, the temperature decreases, and the shrinkage rate of the mother row is larger than that of the bolt, thus forming a gap, which increases the contact resistance. Moreover, as the temperature increases, the contact resistance will become larger, resulting in overheating of the bolt connection. The bolt is screwed Guosong, the mother row contacts badly, the contact resistance is very large, of course, will cause overheating of the connecting part. Therefore, when tightening the butt bolts of the busbar, the tightening degree should be appropriate, generally tightening until the spring washer is flattened. The bolts and nuts of the failed spring washers and sliding buckles should be replaced in time.