In the design and construction of power systems, cable selection is a core link related to safety and efficiency. However, if a cable with a small cross-sectional area is selected due to cost control or lack of experience, the following major hidden dangers may be buried:
1. Overheating and fire: the silent "invisible killer" Joule thermal effect is out of control: insufficient cross-sectional area leads to increased conductor resistance, and excessive heat is generated when current passes through (Q=I²R). If the heat dissipation conditions are poor, the cable temperature rises sharply, and the insulation layer may carbonize, melt or even burn.
2. Voltage drop: "chronic poisoning" of equipment, power supply quality collapse at the end: when transmitting power over long distances, too small a cross-sectional area causes the line voltage drop to exceed the standard (ΔU=IR). At the least, the lights flicker, the motor speed is unstable, and, at the worst, the precision equipment shuts down.
3. Life loss: 90% of the faults are caused by this accelerated insulation aging: long-term overload operation increases the thermal aging rate of insulation materials by 3-5 times. Cables originally designed for a lifespan of 25 years may be at risk of breakdown within 5 years. Maintenance costs doubled: Once an underground cable fails, the excavation and repair costs can be more than 10 times the original cost.
4. Energy waste: The Invisible "black hole" line loss devours profits: If the cross-sectional area is reduced by 50%, the resistance loss will double. If a 500-meter-long 380V line is selected incorrectly, the annual power loss may exceed 20,000 kWh, which is equivalent to throwing away tens of thousands of yuan in electricity bills.
5. Legal liability: If an accident occurs, you will be held responsible. Insurance denial trap: Most engineering insurance clearly excludes losses caused by "design errors", and companies may face huge out-of-pocket compensation.
How to avoid selection disasters?
Accurately calculate load current: Consider correction factors (K value) such as harmonics, ambient temperature, and laying methods Dynamic planning margin: reserve 15%-25% capacity to cope with future expansion needs Full life cycle
Cost analysis: Saving 10,000 yuan in cable fees in the early stage may mean 100,000 yuan in maintenance costs in the later stage
Electrical safety is not a fluke, and the essence of cable selection is the designer's calculation of awe for life. When each conductor's cross-sectional area accurately matches the safety requirements, we can truly build a copper wall to protect the light.
