Power plants, substation switchgear, bus connectors, outdoor knife switch and other important equipment. In the long-term operation, the contacts of the switch and the busbar connection and other parts due to aging lead to excessive contact resistance and fever, and the temperature of these hot parts is difficult to monitor, which eventually led to accidents.
The closed cabinet can not be opened during operation, so it is difficult to measure the actual temperature of the contact (touch) head in operation. If the overheating defects of the touch (touch) head are not found and dealt with in time, it will seriously threaten the safety of electric power production. Fixed switchgear each incoming and outgoing line of a total load current through the 33 or 39 contacts (contacts), trolley mobile switchgear interval of each load share a total load current through the 24 (or more) ( Contact). These access (touch) head directly through the load current, when the load is large, there is a hidden connection (touch) head will be a serious fever. As the hot spot in the sealed cabinet, the operating cabinet door is prohibited to open, on duty personnel can not find the normal monitoring means fever defects. Once the contact fever serious will inevitably cause an accident, affecting the safe operation of the system.
1. At 23:59 on February 3, 2007, a 10kV capacitor bank III644 switch of a substation tripped, and the protection device showed "Overcurrent I segment action". Site inspection found that 10kV distribution room with smoke, 10kV capacitor group III lower switchgear there is a fire phenomenon. The next day check the situation: 10kV capacitor group III 644 B phase switch cabinet and aluminum row loose connection caused by fever led to the Department where the blown and heat-shrinkable material combustion, A, C phase also discharge traces.
2. August 16, 2009 evening, a substation 10kV switchgear failure, burning multifaceted switchgear.
10kV Farm Ⅰ line cabinet (switch, CT, static contact and casing, busbar and docking copper, busbar casing, protection and monitoring devices, screen a small bus, meter, burn the second control cable ; Outlet cable head slightly burned);
10kV white container (busbar, busbar bushing, static contact and casing, protection and monitoring devices, small top screen, watt-hour meter, secondary cable burning; connected copper row, switch, CT, outlet Cable head slight burns);
10kV Hospital Ⅰ cabinet (busbar, busbar bushing, static contact and casing, protection and monitoring devices, screen small bus, watt-hour meter, secondary cable loss; copper connection, switch, CT, outlet Cable head slight burns);
Analysis of the cause of the fault: Switchgear of IkV line in 10kV agricultural special branch has poor contact with isolation plug, and the switch runs at full load for a long time. The contact fever causes the spring of Plum spring to anneal and deform and lose elasticity, causing the contact resistance of the isolated plug to become larger. Burning heat, burn the insulation around the contacts, the final insulation breakdown, resulting in contact short-circuit fault.