How to avoid the accelerated ageing of the cable insulation and damage
Ways to avoid aging of cable insulation
There should be good drainage facilities in cable trenches and cable tunnels, such as shallow water troughs and water collection wells, which can effectively drain water, and automatically set up when necessary, stop the water pumping device, prevent water accumulation, and keep the interior dry. Drainage in cable trenches and longitudinal slopes of tunnels. Prevent water, corrosive gas or liquid, and flammable liquid or gas from entering cables and cable tunnels. The cable tunnel should be naturally ventilated, and bear the normal load of the cable until the temperature of the tunnel is higher than 40-50°C. The ventilation method combining natural ventilation and mechanical ventilation can be adopted. The fan of the ventilation system shall be a fire detector chain to ensure that it can automatically stop when there is fire in the tunnel, and shall not enter the air duct as a cable tunnel ventilation system.
It should be avoided that the cable fire door is in a normally closed state, so that the cable fire barrier is completely sealed, and the sealing effect such as cable ventilation and heat dissipation is filled in the gap between the cable trench cover plate. If the cable is completely closed, the cable cannot be inspected normally, and the fault of the cable cannot be found in time.
According to statistics, cable fire and explosion accidents caused by cable head failure account for about 70% of the total cable accidents. The material and workmanship quality of the hollow cable head must be strictly controlled. The requirements for the service life of the cable head cannot be lower than the service life of the cable. On the street with the rated voltage level and its insulation level, the connecting cable shall not be lower than the rated voltage level and its insulation level. The pressure value between the insulation on both sides of the insulation head shall not be lower than 2 times of the insulation level of the cable protective layer. The form of the joint should be adapted to the setting environmental conditions without affecting the flow capacity of the cable. The length of each side of the cable head is 2 to 3m, and the fire spread treatment should be done within the fire protection range.
Generally speaking, the weak link of the cable insulation cable, so strengthening the monitoring and management of the cable head is an important part of the cable fire. Termination cable heads must not be placed in cable troughs, cable tunnels, cable trays or cable sandwiches between cable heads and must be sorted and tested using various test equipment. The cable head has been found to have abnormal temperature rise or peculiar smell, smoke, and the emergency exit runs early to prevent the running cable from entering the fire field.
In all kinds of cable heads, the length should ensure that there is enough safety distance between two or more cables at the same position of the cable head, and strict sealing measures should be taken between the cable heads of other cables.