There are two possibilities: the contact resistance is too large due to the loose terminal, which leads to overheating; the terminal is not loose, but the loop is over-current and heated for some unknown reason, such as the power supply voltage is too high, or the load is short-circuited.
1. The voltage is too high. It can be checked from the source, the secondary voltage of the transformer - the voltage in the distribution box - the voltage of each electrical equipment.
2. Ground fault. It can also be checked from the transformer, and then grounded to the distribution box. The grounded one should be grounded, and the normal phase line should be excluded from the ground fault. You can use an insulation meter or a shaker to measure when the power is off, and measure in sections. Try to measure only the power supply and distribution lines such as cables, wires, circuit breakers, switches, etc. in sections. Fuses for sensing devices.
The key to grounding is that the grounding resistance should be low and the contact area should be large. The former can ensure that the grounding point has a "zero potential" as low as possible close to the ground potential, which can avoid the possibility that the lightning will "reverse" from the grounding wire and enter the power supply circuit after a thunderstorm. The latter can ensure that there is sufficient capacity to provide a fault current path, including lightning or short-circuit faults, etc. Because the actual construction process has theoretically changed according to the changes of contemporary technology and technology, whether this grounding method is feasible or not depends on how the new standard specification is stipulated.
